Car fault diagnostics (BMW 7 Series E38)

Description of diagnostics of electronic control systems and fault codes are given in Chapter Engine electrical systems.

This section offers the simplest scheme for identifying the causes of malfunctions and failures occurring in vehicle components and systems. Failures and their possible causes are divided into groups based on their relationship to specific vehicle components or systems, such as the engine, cooling system, etc., and the text also provides references to chapters and sections related to these issues.

Remember that successful troubleshooting is determined by the integrity of a good body of knowledge and a patient, systematic approach to problem research. Always move from simple to complex, bring each check to its logical conclusion and try not to miss obvious facts - anyone can forget to fill the fuel tank or leave the lights on overnight.

Finally, you should always try to get a clear picture of the progression of the fault and take appropriate steps to prevent a recurrence. If the electrical equipment failure occurred due to a poor contact quality, check the condition of all other contacts and electrical connectors in the system at the same time. If the same fuse has blown several times in a row, there is no point in replacing it further - try to find out the cause of the failure. Remember that the failure of a minor component may be a sign of a malfunction of a more important unit or the entire system.

Engine

Mandatory conditions for starting any gasoline engine are the proper supply of air-fuel mixture to the cylinders and adequate spark formation at the spark plugs.



First of all, you should make sure that the fuel supply is working properly.

To determine whether a spark is formed, remove the spark plugs, insert them into the tips and apply them individually to ground. Do not hold the wire or tip with your hands - use insulated pliers. Ask an assistant to start the engine. If there is no spark, try to determine the cause of the failure.

The engine does not turn over when trying to start it

1. The battery terminals are oxidized or the wire tips are loose.

2. The battery is discharged or defective. If the cable ends are not corroded and are securely connected to the battery terminals, turn the ignition key to the "ON" position, then turn on the headlights and/or windshield wipers - if they do not work, the battery is discharged.

3. The transmission is not accurately set to the "P" position (AT) or to neutral gear (manual transmission), or the clutch is not fully depressed.

4. Break in the starting system circuit.

5. The starter gear is jammed in the toothed ring of the drive disk/flywheel.

6. The starter traction relay is faulty.

7. Starter is faulty.

8. The ignition switch is faulty.

The engine turns over but does not start

1. The launch is not performed correctly (see section Operating techniques and auxiliary systems Chapters Controls and operating techniques).

2. The engine immobilizer is faulty or not disabled.

3. The fuel pump emergency switch is faulty.

4. The fuel tank is empty or filled with low-quality fuel.

5. The air filter is heavily soiled. There are vacuum leaks in the air supply elements, malfunctions in the fuel injection and ignition control systems.



6. The battery is discharged (the engine turns over too slowly).

7. The battery terminals are oxidized or the wire ends are loose.

Gasoline engine

1. The fuel pump is faulty, or its relay is damaged - check by ear that the pump is turned on when the ignition is turned on.

2. Ignition system components are damaged or excessively damp.

3. Spark plugs are worn or faulty, or the spark plug gap is set incorrectly.

4. Break in the starting system circuit.

5. The engine control unit fuse is damaged, one of the engine control system sensors is faulty.

6. Low compression pressure.

Diesel engine

1. The engine is not warmed up: check the proper functioning of the pre-heating system.

2. The fuel injection start adjustment is out of adjustment. Check and make adjustments.

3. The injectors are faulty. Check. Loosen the union nuts one by one - when you loosen the nut of the faulty cylinder, the engine speed will not drop.

4. The high-pressure fuel pump (HPFP) is faulty. Install a known good HPFP for testing.

5. There is no voltage on the electromagnetic (EM) shut-off valve. Connect a voltmeter or LED tester to the switch. Turn on the ignition. The LED should light up. Otherwise, you should find the break in the wiring and fix it.

6. The electromagnetic shut-off valve is faulty. Check the reliability of the electromagnetic switch fastening, check the contacts. Turn the ignition on and off. A click should be heard in the switch.

7. There is damage in the fuel supply line or air in the lines:

• The lines or hoses are mechanically damaged or clogged. Clean the fuel lines and remove air from the lines and filter;
• The fuel filter is clogged. Replace the filter element;
• In winter, check the filter and lines for ice or wax. Put the car in a heated garage, add gasoline to the system;
• The tank ventilation or fuel intake mesh filter is clogged. Clean it.

The starter operates without turning the engine

1. The starter gear is jammed.



2. The starter gear teeth or flywheel/drive disc ring gear are worn or damaged.

Difficulty starting a cold engine

See also Section Cold engine starts poorly, runs unsteadily.

1. Low battery level.

2. The functioning of the power supply system components or electrical equipment is disrupted.

Difficulty starting a hot engine

See also Section Warm engine starts poorly and runs unsteadily.

1. The air filter is clogged.

2. The functioning of the power supply system components or electrical equipment is disrupted.

3. Fuel is not supplied to the fuel injectors.

4. Insufficient compression in the cylinders.

The starter engages too noisily or with difficulty

1. Starter gear teeth or flywheel/drive disc teeth are worn or damaged.

2. The starter mounting bolts are missing or not tightened enough.

The engine starts but immediately stalls

1. The engine immobilizer is faulty.

2. The electrical wiring is faulty, or the wires on the terminals of the ignition coil or generator are loose.

3. The functioning of the power supply system components or electrical equipment is disrupted.

4. The basic settings of the engine control unit (ECM) are violated.

5. There is damage to the exhaust and emission control system.

6. There are losses of vacuum at the throttle body, intake manifold or through vacuum hoses.

The stability of the engine at idle speed is impaired

Gasoline engine

1. There is a loss of vacuum. Make sure that the fasteners are tightened securely, check the fact and quality of fastening on their nipples on the intake manifold of all vacuum hoses. Listen to the running engine with a stethoscope or a section of fuel hose - the presence of a hissing sound indicates a leak. Using a soap solution for checking is no less effective.



2. The functioning of the components of the power supply system or electrical equipment is disrupted.

3. The crankcase ventilation (PCV) valve is clogged.

4. The air filter is clogged.

5. The fuel pump does not supply sufficient fuel to the injectors.

6. There are leaks through the cylinder head gasket - measure the compression in the engine cylinders (see Engine).

7. The working projections of the camshaft cams are worn out.

Diesel engine

1. The quality of the connections of the fuel hoses with the high-pressure fuel pump and fuel filter is damaged. Replace the fuel hoses, secure them with clamps, tighten the screws of the corner connections.

2. The fuel injection pump mount is mechanically damaged or loose.

3. The connections of the return line and the fuel supply line are reversed.

4. There is damage in the fuel supply line:

• The pipes or hoses are mechanically damaged or clogged. Clean the fuel pipes;
• The fuel filter is clogged. Replace the filter element;
• In winter, check the filter and lines for ice or wax. Put the car in a heated garage, add gasoline to the system;
• The tank ventilation or fuel intake mesh filter is clogged. Clean it.

5. Fuel injection start adjustment is out of adjustment. Check and make adjustments.

6. The injectors are faulty. Check. Unscrew the union nuts one by one - when you unscrew the nut of the faulty cylinder, the engine speed will not drop.

7. The fuel injection pump is faulty. Install a known good fuel injection pump for testing.

There are misfires in the cylinders at idle speed

1. Spark plugs are worn or dirty, or the spark plug gap is set incorrectly.



2. There is a malfunction of the power supply system components or electrical equipment.

3. The high-voltage wiring is faulty.

4. Poor quality fuel has been added or the fuel filter is clogged.

5. There are losses of vacuum in the intake manifold or through hose connections.

6. Low or unevenly distributed compression in the cylinders.

7. The engine control system is malfunctioning.

There are misfires in the engine cylinders when the car is moving in gear

1. The fuel filter is blocked or the fuel system is contaminated.

2. The spark plugs are faulty or dirty, or the spark plug gap is set incorrectly.

3. There is a malfunction of the power supply system components or electrical equipment.

4. The high-voltage wiring is faulty.

5. The components of the exhaust gas toxicity reduction system are faulty.

6. Low or unevenly distributed compression in the cylinders.

7. The ignition system is faulty.

8. There are vacuum losses at the throttle body, intake manifold or through vacuum hoses.

The engine stalls spontaneously

1. Idle speed adjustment is incorrect.

2. The fuel filter is clogged, or moisture or dirt has entered the fuel system.

3. There is a failure of components/information sensors of the power supply system.

4. Components of exhaust gas toxicity reduction systems are faulty.

5. The spark plugs are faulty or dirty, or the spark plug gap is set incorrectly.

6. There are losses of vacuum at the throttle body or through the vacuum hoses.

The engine does not develop full power

1. There is a malfunction of the power supply system components or electrical equipment.

2. The air cleaner is clogged.

3. The spark plugs are faulty or the spark plug gap is set incorrectly.

4. The ignition coil is faulty.

5. The ATF level has dropped (see chapter Vehicle settings and routine maintenance).

6. Clutch/AT slips.

7. The fuel filter is blocked and/or dirt/moisture has entered the fuel system.

8. The fuel used was of poor quality.

9. The turbocharger control valve is damaged.

10. Low or unevenly distributed compression in the cylinders.

Additional for diesel engine

1. Uneven fuel supply from the high-pressure fuel pump to the cylinders. Adjust on a warm engine.

2. The moment of start of fuel supply of the high-pressure fuel pump is set incorrectly. Adjust.

3. The fuel filter or high-pressure fuel pump (injector) is clogged. Wash the pre-filter, change the fine filter element, clean the sprayer or replace the pump (injector).

4. The maximum crankshaft speed adjustment is not correct.

There are pops in the intake system or shots in the exhaust system

1. The functioning of the components of the power supply system or electrical equipment is disrupted.

2. There is a defect in the secondary circuit of the ignition system (destruction of spark plug insulators or damage to high-voltage wires).

3. The fuel injection system needs adjustment, or its components are excessively worn.

4. There are vacuum losses at the throttle body, intake manifold or through vacuum hoses.

5. The valves are stuck.

6. The order of connecting the I/O wires is violated.

When accelerating or driving uphill, detonation sounds occur

1. The fuel used was of poor quality.

2. The functioning of the components of the power supply system or electrical equipment is disrupted.

3. The wrong type of spark plugs are installed.

4. The basic ECM settings are violated.

5. The knock sensor is faulty.

6. There are losses of vacuum.

The engine continues to run after turning the key to the "OFF" position

1. Idle speed is too high.

2. There is a malfunction in the electrical equipment or components of the engine control system.

3.The fuel Vapor Capture system (EVAP) purge valve is defective.

4. High engine operating temperature (coolant level dropped, thermostat is faulty, radiator is blocked or water pump is faulty).

5. The injectors are not sealed properly.

Diesel engine smokes

1. Black smoke:

• The air cleaner is dirty. Replace the filter element;
• Incorrect fuel used. Flush tank and change fuel;
• The moment when the fuel injection pump starts to supply fuel is set incorrectly.

2. Blue smoke:

• Oil burning in the combustion chamber due to worn piston rings, high oil level in the air cleaner, worn seals in the turbocharger covers, leaks in the gasket between the crankcase and the turbocharger. Repair the engine, adjust the oil level, replace the seals, tighten the turbocharger mounting bolts or replace the gasket;
• No fuel is supplied to one of the injectors. Check by heating the outlet pipes of the manifold;
• Poor fuel atomization by the injector due to a faulty valve or a broken atomizer. Grind the valve or replace the injector.

3. White or brown smoke:

• Low temperature in the cooling system. Check the thermostat;
• Poor operation of the injectors due to wear or breakage of the atomizer. Replace the atomizer.

Engine electrical equipment

Reduced capacity or insufficient battery charge

1. The generator drive belt is worn or damaged, or its tension adjustment is incorrect.

2. The electrolyte level is insufficient or the battery is very discharged.

3. The battery terminals are oxidized or the wire tips are loose.

4. The generator does not provide the required charging current.

5. Break in the charging circuit wiring.

6. A short circuit to ground in the electrical wiring creates a constant leak of current generated by the battery.

7. There is an internal defect in the battery.

The charge indicator lamp does not go out when the revs increase

1. The drive belt tension is loose.

2. The voltage regulator and/or generator is damaged.

3. The generator brushes are worn out.

4. The wire between the generator and the voltage regulator is damaged.

5. The instrument cluster is faulty.

The charge indicator lamp does not light when the key is turned to the "ON" position

1. The control lamp is out of order.

2. The generator is faulty.

3. There is a defect in the printed circuit board, wiring inside the instrument cluster unit, or lamp socket.

The charge indicator lamp does not go out when the key is turned to the "OFF" position

1. The diodes are broken.

Starter

The electrical wiring terminals must be securely fastened and not oxidized!

1. If the starter does not turn, first make sure that there is voltage at terminal No.50 of the traction relay (minimum 10 V). If the results are negative, check the condition of the starter current circuit wiring.

2. To check the starter's operation at full battery voltage, do the following:

• Without engaging gears, turn the key to the "ON" position;
• Short-circuit terminals 30 and 50 of the starter with a wire with a cross-section of at least 4 mm².

3. If the starter works perfectly, the cause of the malfunction should be sought in the wires to the starter. If the starter does not work, it should be checked with it removed.

The starter does not turn when the key is turned to the "START" position

1. The battery is low.

2. Short-circuit terminals 30 and 50 of the starter: if it rotates, check the wire 50 connected to the ignition switch for a break, and also assess the condition of the starter switch.

3. The ground wire is broken or the quality of its terminal connection is poor.

4. Weakening of current strength due to poor quality or oxidation of contact connections.

5. There is no voltage at terminal 50 of the traction relay as a result of a break in the electrical wiring or damage to the starter switch.

The starter rotates slowly and does not turn the crankshaft

1. The battery is low.

2. Summer oil is poured in.

3. The flow of current is difficult due to poor quality contacts.

4. Carbon brushes do not fit tightly against the collector, are stuck in the guides, are worn out, broken, oily or dirty.

5. Insufficient distance between the brushes and the commutator.

6. The collector is grooved or burnt and oily.

7. No voltage at terminal 50 (minimum 8 V).

8. The bearing is broken.

9. The traction relay is faulty.

The starter "grabs", but only provides jerky engine cranking

1. The gear drive is faulty.

2. The gear is dirty.

3. The toothed ring of the drive disk is damaged.

Starter pinion does not disengage from flywheel/drive disc ring gear

1. The gear drive components are dirty or damaged.

2. The traction relay is faulty.

3. The return spring is weak or broken.

The starter continues to operate after the ignition key is released

1. The traction relay is jammed - immediately turn off the ignition and replace the traction relay.

2. The ignition switch does not turn off - disconnect the battery, replace the switch.

Power supply system

Excessive fuel consumption

1. The air filter is dirty or blocked.

2. Tire inflation pressure is insufficient or tires of the wrong size are installed.

3. The engine has mechanical damage. Check the compression, if necessary, carry out the appropriate restoration repair.

4. Idle speed and maximum crankshaft speed are excessively high.

5. There is a malfunction of the power supply system components, electrical equipment or electronic control.

6. Leaks in the air intake system.

7. There is damage to the exhaust system and a reduction in exhaust toxicity.

8. Additional for diesel engine: Clogged return line. Blow air through the return line from the injection pump to the fuel tank.

There are fuel leaks and/or the smell of gasoline

1. There are leaks in the fuel supply lines or vent lines.

2. The fuel tank is full. Refuel only until the gun switches off automatically.

3. There are leaks/evaporation from the fuel and exhaust gas lines.

The engine does not start

1. When the starter is turned on, the fuel pump does not work (the noise of its operation cannot be heard). Lightly tap the pump body to release the jammed part. Check the correctness of the voltage supply to the pump (check the serviceability of the fuse and the reliability of the fastening of the contact terminals of the corresponding electrical wiring).

2. The fuel pump relay is faulty.

3. The injector valves are stuck. Check the injectors, replace if necessary. Check the voltage supply to the injectors.

4. There is no signal from the ignition sensor or ECT sensor. Check the condition of its wiring, query the OBD system memory.

5. Fuel lines are damaged, clogged or leaky, there are defects in the hoses.

6. The fuel filter is clogged.

7. As a result of a leak, excess air is sucked into the intake tract.

8. Vacuum pipes are damaged or their tightness is compromised.

9. The fuel pressure regulator is damaged - check the residual pressure.

10. The throttle position sensor (TPS) is damaged.

11. No power to ECM.

12. The fuel tank ventilation lines are clogged, the filter in the tank is clogged.

13. Presence of ice or wax in the filter or diesel engine lines.

14. The preheating system does not work.

15. The diesel engine fuel shut-off valve is damaged.

16. The moment of start of fuel supply is disrupted.

17. The diesel engine injectors are damaged. Loosen the union nuts one by one and check if the corresponding cylinder works.

18. The fuel injection pump is faulty.

Cold engine starts poorly, runs unsteadily

1. The CO content does not meet the standard requirements - make the appropriate measurement, check the idle speed.

2. The ECT sensor is faulty.

3. The fuel pressure does not meet the required value.

4. As a result of a leak, excess air is sucked into the intake tract.

Warm engine starts poorly and runs unsteadily

1. The air intake system is leaky. Check the intake system. To do this, let the engine idle and wet the seals and connections on the intake tract with gasoline. If the speed increases briefly, eliminate the leaky areas.

2. The fuel pump check valve is damaged.

3. Leaks in the fuel system.

4. Increased fuel pressure in the fuel system.

5. EVAP system malfunction.

6. The return fuel line to the tank is clogged or crushed.

7. The injector valves are stuck. Check the injectors, replace if necessary. Check the voltage supply to the injectors.

8. No signal from the Hall ignition sensor or coolant temperature sensor. Check the condition of the corresponding wiring, perform a survey of the OBD II system.

9. As a result of a leak, excess air is sucked into the intake tract.

10. The pressure regulator is damaged - check the residual pressure.

11. The TPS sensor is damaged.

12. No power to ECM.

The engine runs intermittently

1. Fuel pump wiring connections are intermittently loose. Check wiring connectors and fuses for the fuel pump, MAF sensor, and fuel pump relay.

2. Low fuel quality, formation of vapor locks.

3. Weak fuel supply.

4. The fuel filter is faulty.

5. The fuel pump is faulty.

6. The injectors are faulty.

7. The lambda probe is faulty, there are problems in the mixture quality control circuit, or the lambda probe is not heated.

8. TPS is faulty.

9. The exhaust manifold or exhaust pipe is damaged (there are exhaust gas leaks).

10. EVAP system malfunction.

11. The injector valves are stuck. Check the injectors, replace if necessary. Check the voltage supply to the injectors.

12. No signal from Hall Effect Ignition Sensor or ECT Sensor. Check wiring, query ECM memory for fault codes.

13. As a result of a leak, excess air is sucked into the intake tract.

14. Vacuum lines are damaged or leaky

15. The pressure regulator is damaged - check the residual pressure.

16. No power to ECM.

The engine runs intermittently in transient modes and in idle mode

1. The air intake system is leaky. Check the connections of the intake system. Start the engine and wet the connections of the intake tract components with gasoline. If the engine speed increases briefly, eliminate the cause of the leak.

2. Incorrect idle speed adjustment. Check TPS and lambda adjustment.

Hot engine won't start

1. Incorrect adjustment of CO content. Check CO content and idle speed.

2. Too high pressure in the fuel system - check the fuel pressure, replace the pressure regulator if necessary.

3. The return line between the pressure regulator and the fuel tank is clogged or bent. Clean or replace the line.

4. The engine temperature sensor is faulty.

5. The tightness of the power supply system is broken.

6. The air intake tract is not sealed.

The engine runs after being turned off

1. Injectors are leaky. Check injectors.

2. The fuel shut-off valve on the diesel engine does not work.

Lubrication system

The indicator lamp does not light when the key is turned to the "ON" position

1. The oil pressure sensor is faulty. Turn on the ignition, disconnect the wire from the sensor and short it to ground - if the lamp lights up, replace the sensor.

2. There is no voltage supplied to the sensor, the contacts are corroded - check the condition of the corresponding electrical wiring.

3. The control lamp is faulty.

4. The instrument cluster is faulty.

The indicator light does not go out after starting the engine

1. The oil is overheated. If the indicator lamp goes out after gas is supplied, nothing needs to be done.

The indicator lamp does not go out after gas is supplied, or lights up while driving

1. The oil level has dropped.

2. There is a short circuit in the oil level sensor wiring.

3. The sensor is faulty.

Oil pressure too low at all speeds

1. The oil level has dropped.

2. The mesh filter of the oil intake in the oil pan is clogged.

3. The oil pump is worn out.

4. The crankshaft bearings are damaged.

Too low oil pressure at low speeds

1. The pressure reducing valve is stuck open due to contamination.

Oil pressure too high at engine speeds above 2000 rpm

1. The pressure reducing valve does not open due to contamination.

Cooling system

Overheat

1. The coolant level has dropped.

2. The water pump drive belt is worn or damaged, or its tension adjustment is incorrect.

3. The internal radiator channels are blocked or the radiator grille is dirty (obstructed).

4. The thermostat is faulty.

5. The fan impeller blades are broken or cracked.

6. The fan clutch is faulty.

7. The coolant temperature gauge is faulty.

8. The water pump is faulty.

9. The radiator cap does not hold pressure - check the cap under pressure.

Hypothermia

1. The thermostat is faulty.

2. The coolant temperature gauge readings are inaccurate.

External coolant leaks

1. The hoses are damaged or destroyed as a result of aging of the material, or their fastening on the fittings has become loose.

2. The water pump seals are damaged - coolant leaks through the inspection hole in the pump body.

3. There are leaks from the internal channels of the radiator or reservoir.

4. There are leaks through the engine drain plug or the release plugs of the water galleries.

Internal coolant leaks

Internal coolant leaks are usually detected by checking the engine oil. Inspect the dipstick blade and the inside surfaces of the cylinder head(s) for traces of water and oil foaming.

1. There are leaks through the cylinder head gasket - check the cooling system under pressure.

2. There are cracks in the cylinder walls or in the head casting.

Coolant losses occur

1. There is too much coolant in the system.

2. The coolant boils away as a result of engine overheating.

3. There are internal or external coolant leaks.

4. The radiator cap is faulty - check the cap with pressure.

Coolant circulation is disrupted

1. The water pump is not functioning properly.

2. The cooling system is clogged - flush it and fill it with fresh fluid. If necessary, remove the radiator and perform a reverse-flow flush.

3. The water pump drive belt is worn or damaged, or its tension adjustment is incorrect.

4. Thermostat is stuck.

Heater

The heater fan does not work

1. The fan electric motor fuse is faulty.

2. The fan switch is faulty - check if voltage is supplied to the pre-resistors, remove and check the fan switch.

3. The fan electric motor is faulty. Check if voltage is supplied to it with the ignition on and the fan switch closed - if voltage is supplied, replace the motor.

The heater fan does not work at one of the stages

1. The pre-resistor is faulty.

The heater does not turn off with the regulator

1. The switch is faulty.

2. The control mixing flap cables are damaged or do not move well.

Heating power too low

1. The coolant level is insufficient.

2. The heater control handles are difficult to operate, faulty - check the control assembly, replace the corresponding drive cable if necessary.

Noise in the area of the heater fan

1. Dirt or leaves got in - remove the fan and clean it, clean the air duct.

2. The impeller is out of balance and the bearing is damaged.

Clutch

The clutch does not disengage (the manual transmission control lever does not move freely to the reverse gear position and back when the clutch pedal is pressed to the floor)

1. The clutch disc is bent or damaged (see chapter Cardan and drive shafts, gearbox, differential and hub assemblies).

The clutch is slipping (engine speed increases without increasing vehicle speed)

1. The clutch disc is oily or its friction linings are worn. Remove the clutch (see chapter Cardan and drive shafts, gearbox, differential and hub assemblies) and check the condition of its components.

2. The clutch disc has not been properly run in. It may take 30 to 40 normal car starts to completely run in a new disc.

3. The pressure plate/clutch basket is worn out (see chapter Cardan and drive shafts, gearbox, differential and hub assemblies).

There is a strong vibration when the clutch is engaged

1. The clutch disc is oily. Remove the clutch and check the condition of its components. Eliminate any leaks found.

2. The splines of the driven disk hub are worn out (clutch disc). Remove the clutch and check the condition of its components.

3. The pressure plate/clutch basket or flywheel is bent. Remove the clutch and check the condition of its components and the flywheel.

Jerks when engaging the clutch

1. Damage to engine and gearbox mounts. Check and replace if necessary.

2. Looseness of the gearbox mounting to the suspension. Tighten the mounting bolts.

3. Uneven contact of the pressure plate. Replace the clutch basket.

4. The crankshaft is not aligned with the gearbox. Check the alignment.

A squealing or rattling noise occurs when the clutch is fully engaged (pedal released)

1. The clutch release bearing is seized. Remove the clutch and inspect the bearing. Remove any burrs and burrs, and lubricate the bearing before reinstalling.

A squealing or rattling noise occurs when the clutch is fully disengaged (the pedal is pressed)

1. The release bearing is worn or damaged (see chapter Cardan and drive shafts, gearbox, differential and hub assemblies).

2. The springs are worn or damaged (or aperture blades) pressure plate in the clutch basket (see chapter Cardan and drive shafts, gearbox, differential and hub assemblies).

The clutch pedal remains depressed to the floor after it is released

1. The piston of the clutch master or slave cylinder is jammed. Damage to the clutch hydraulic system or release bearing. Check the condition, remove the clutch components if necessary.

Manual transmission (MT)

When the manual transmission is set to neutral, extraneous noises occur while the engine is running

1. The input shaft bearing is worn out.

2. The bearing of the driven shaft drive gear is damaged.

3. The intermediate shaft bearings are worn out.

4. The intermediate shaft axial play adjustment washers are worn or damaged.

Extraneous noises occur in any position of the manual transmission

1. Any of the above reasons and/or:

2. There is not enough transmission oil in the manual transmission (his level dropped).

Extraneous noises occur in a particular gear

1. The gear teeth of this transmission are worn, damaged or chipped.

2. The synchronizer of this gear is worn out or damaged.

The manual transmission "jumps" out of the highest gear

1. Dirt has gotten between the gearbox and the engine, or the gearbox has shifted relative to the engine.

Difficulties occur when shifting gears

1. The clutch is not fully depressed (disengaged).

2. The shift rod is damaged, loosened or out of adjustment. Carefully check the condition of the components and replace any defective ones if necessary.

There are transmission oil leaks

1. There is too much transmission oil in the manual transmission. Drain the excess if necessary.

2. The differential seals need to be replaced.

Automatic transmission (AT)

Due to the complexity of the AT design, it is advisable to diagnose its faults and repair its components in a car service workshop.

Common problems associated with the operation of the switching mechanism

1. The following can be attributed to failures associated with a malfunction of the shift rod adjustment:

2. The engine can be started in transmission positions other than "P" and "N";

3. The transmission position indicator readings differ from the actual gear selected;

4. The vehicle is moving with the transmission in position "P" or "N";

5. Gears shift with difficulty or randomly.

6. Adjust the gear shift rod.

The transmission slips, shifts with difficulty, makes extraneous noises, or does not allow the vehicle to move when shifted into one of the gears

1. There are many possible causes for the problems listed in the title, but only one of them falls within the competence of the amateur mechanic - incorrect transmission fluid (ATF) level.

2. Before driving the car to the auto service workshop, check the level and condition of the ATF. Correct the ATF level or change it.

There are transmission fluid (ATF) leaks

1. ATF is dark red in color. Its leaks should not be confused with engine oil, which can be carried to the transmission housing by the oncoming air flow.

2. To identify and localize the source of the leak, first remove all traces of dirt and grease from the transmission housing. Use a suitable degreaser and/or steam clean. Then drive the vehicle for a short time at low speed (so that traces of a leak are not carried away by the oncoming flow far from its source). Stop, jack up the car and visually inspect to determine the source of the leak. Most often, these are:

3. Transmission oil pan - tighten mounting bolts and/or replace oil pan gasket;

4. ATF filler tube - replace the rubber seal where the tube enters the transmission housing;

5. ATF lines - tighten fittings or replace lines;

6. Vent tube - the transmission is overfilled and/or water has entered it.

ATF is brown or smells burnt

1. ATF level is insufficient.

Kickdown mode does not turn on when the pedal is fully pressed (the downshift does not engage)

1. The ATF level has dropped.

2. The engine management system is faulty.

3. The sensor switch or its wiring is faulty.

4. The selector drive cable is out of adjustment.

The engine does not start in any selector position or starts in positions other than "P" and "R"

1. The adjustment of the start permission switch sensor is disturbed.

2. The engine control system is not functioning properly.

3. The selector cable adjustment is incorrect.

Transmission slips, jerks or makes noise when shifting gears. Car does not move when in "D" or "R" mode

1. The ATF level has dropped.

2. The sensor or its wiring is faulty.

3. The engine control system is not functioning properly.

Bridges

Extraneous noises

1. Normal road noise - cannot be corrected.

2. Tire noise - check the condition of the treads and tire inflation pressure.

3. Wheel bearings are worn or damaged, or their tightening force has weakened.

Vibrations

1. Check the condition of the wheel bearings by alternately jacking up the corresponding corner of the car and rotating the wheel manually. Listen to the sounds coming from the bearing. Remove the bearings and check their condition.

Oil leaks

1. Differential seals are damaged.

Brake system

Before you come to a final conclusion about the presence of problems with the braking system, make sure that the tires are in satisfactory condition and inflated to the required pressure, the front wheel alignment is not out of alignment and the vehicle is not loaded unevenly.

Increased brake pedal travel

1. The working circuit of the brake tract is damaged - check the system for leaks.

The brake pedal springs and sinks

1. Air has entered the brake system - bleed the system.

2. The fluid level in the master cylinder reservoir has dropped - make the appropriate adjustments, bleed the system.

3. Formation of steam bubbles. Occurs mainly under heavy load on the brakes. Replace the brake fluid, remove air from the system.

Reduced braking effect, pedal falls through

1. The hydraulic circuit is not sealed.

2. The seals in the main or working brake cylinders are damaged.

3. The rubber gasket is damaged. Repair the caliper.

Poor braking despite high pedal force

1. Brake linings are oily.

2. Incorrect or hardened pads are installed.

3. The brake booster is faulty.

4. The brake pads are worn out.

When braking, the car pulls to the side

1. The tire inflation pressure is not correct.

2. The treads are unevenly worn.

3. Brake linings are oily.

4. Different brake pads are installed on the same axle.

5. Brake pads are excessively worn.

6. The caliper shafts are dirty.

7. The calipers are damaged by corrosion - replace them.

8. Brake pads are worn unevenly.

Spontaneous braking

1. The compensation hole in the master brake cylinder (MBC) is clogged.

2. The clearance between the drive rod and the master cylinder piston is insufficient.

Brakes get hot while driving

1. The compensation hole in the master brake cylinder is clogged.

2. The clearance between the drive rod and the master cylinder piston is insufficient.

The brakes are shaking

1. The wrong type of brake pads are installed.

2. The brake disc is corroded in places.

3. The brake disc runout is excessive.

The brake pads do not move away from the brake disc, the wheel is difficult to turn manually

1. Corrosion in brake caliper cylinders. Repair or replace the caliper.

Uneven wear of brake pads

1. The wrong type of brake pads are installed. Replace the pads.

2. The calipers are damaged by corrosion - replace them.

3. The piston stroke is difficult.

4. The tightness of the brake system tract is broken.

Wedge-shaped wear of brake pads

1. The brake disc does not rotate parallel to the caliper.

2. The calipers are damaged by corrosion - replace them.

3. The piston is not functioning properly.

Squeaking brakes

1. Often the reason is atmospheric influence (air humidity). If the creaking appears after a long period of standing in high humidity and then disappears, there is no need to do anything.

2. The wrong type of brake pads are installed.

3. The brake disc does not rotate parallel to the caliper.

4. The caliper shaft is dirty.

5. The brake shoe mounting springs are bent.

6. The pressure springs are stretched.

Brake pedal pulsation

1. Sign of normal ABS operation.

2. The brake disc runout is excessive.

3. The brake disc does not rotate parallel to the caliper.

ABS warning light comes on while driving

1. The supply voltage is insufficient (below 10 V). Check the voltage. Check whether the generator indicator lamp goes out after the engine starts. If everything is OK, check the generator drive belt.

2. There is a fault with the ABS - check the condition and reliability of the clamp connection of the ground of the return pump (in the hydromodulator).

Suspension and steering

The car pulls to one side when moving

1. Tires are unevenly inflated.

2. There is a defect in the tires.

3. Excessive wear of suspension or steering components.

4. It is necessary to adjust the front wheel alignment angles.

5. The front brakes are seized.

There is jerking, twitching or vibration

1. Wheel balance is disturbed or rims are out of ovality.

2. Wheel bearings are worn out, their tightening force has weakened, or their adjustment is out of order.

3. Shock absorbers or other suspension components are worn or damaged.

There is excessive rocking of the car/its nose "digging" in when turning or braking

1. Suspension struts are faulty.

2. Suspension components are damaged.

The steering wheel is too hard to turn

1. The fluid level in the power steering reservoir has dropped excessively.

2. The tires are not inflated correctly.

3. The steering linkage joints are not sufficiently lubricated.

4. The front wheel alignment angles are out of adjustment.

5. The power steering does not develop the required power.

There is excessive play in the steering

1. The tightening force of the front wheel bearings has weakened.

2. Excessive wear of suspension or steering components.

The power steering does not develop the required force

1. The power steering pump drive belt is worn out or damaged, or its tension adjustment is incorrect.

2. The power steering fluid level has dropped excessively.

3. The patency of the hoses or lines of the hydraulic system is impaired.

4. Air has entered the power steering system - bleed the system.

There is excessive wear on the treads (not in one particular area)

1. The tires are not inflated correctly.

2. Wheel balance is disturbed.

3. The wheel rims are damaged.

4. Excessively worn suspension or steering components.

There is excessive wear on the outer edge of the treads

1. The tires are not inflated correctly.

2. Turns are made too sharply.

3. The front wheel alignment angles are out of adjustment (excessive convergence).

4. The suspension arm is bent or twisted.

There is excessive wear on the inner edge of the treads

1. The tires are not inflated correctly.

2. The front wheel alignment angles are out of adjustment (divergence).

3. Steering components are damaged or loose.

There is localized wear of the tread

1. Wheel balance is disturbed.

2. The discs are damaged or bent.

3. There is a defect in the tires.

Windscreen wiper blade defects

Slippage

1. Rubber working elements are dirty.

2. The edges of the brushes are frayed, the rubber working elements are worn out or torn.

In the cleaning field, the remaining water immediately collects into drops

1. The windshield is contaminated with varnish or oil.

The brush cleans one-sidedly - one way is good, the other is not

1. The rubber working element has one-sided wear.

2. The windshield wiper arm is twisted, the blade does not fit precisely to the glass.

Uncleaned surfaces

1. The reliability of the working element fixation in the brush frame is compromised.

2. The brush does not adhere evenly to the glass.

3. The lever pressing force is too low - lightly lubricate the wiper arm hinges and springs or install a new arm.

Tyre defects

Severe tire wear on both sides of the working surface

1. Tire pressure is too low.

Severe wear of the tire in the middle of the working surface along the entire circumference of the tread

1. Tire pressure is too high.

Uneven tread wear

1. Static and dynamic imbalance of the wheel, possibly due to excessive lateral runout of the disc, too much play in the bearing joints.

Uneven wear in the middle of the tread

1. Static wheel imbalance, possibly due to excessive vertical runout.

Severe wear of individual areas in the middle of the tread working surface

1. The result of sudden braking.

Saw-tooth wear of the tread, often accompanied by an invisible tear in the fabric base of the tire

1. Vehicle overload. Check the condition of the inner walls of the tires.

Rubber tongues on the side edges of the tread (scaly wear)

1. Wheel alignment is incorrect.

2. The tires are worn out.

3. Shock absorbers/torsion springs/strut assemblies are faulty.

Formation of burrs on one side of the front wheel tread

1. Wheel alignment is out of adjustment.

2. The tires are worn out.

3. Frequent movement on wavy surfaces. Fast movement on turns.

Cord breaks. At first only visible from the inside

1. Driving over sharp rocks, tire impacts, etc. at high speed.

One-sided wear of the working surface of the tread

1. Check the camber adjustment.

2. There is a fault with the ABS - check the condition and reliability of the clamp connection of the ground of the return pump (in the hydromodulator).