Troubleshooting Automatic Transmission (BMW 3 Series E46)

Note: Due to the complexity of the automatic transmission, it is not possible for the vehicle owner to check and service it. For problems not described below, the vehicle should be taken to a dealer or an automatic transmission specialist. Do not rush to remove the transmission if you suspect a problem, as most checks can be performed without removing it from the vehicle.

Transmission fluid leak

Transmission fluid is usually dark in color. Leaks should not be confused with engine oil, which can easily be carried into the transmission by air flow.

To locate the source of the leak, remove all dirt from the transmission housing and surrounding area with steam or a degreaser. Drive the car at low speed so that the air flow does not carry the leaking fluid away from the source of the leak. Raise and support the car and locate the leak. The most common leak locations are:

• a) Transmission oil pan (chapters 1 and 7B).
• b) Dipstick connection (chapters 1 and 7B).
• c) Pipes/connections of the joints of the transmission with its radiator (chapter 7B).

Transmission fluid is brown or has a burnt odor

• Low transmission fluid or need to be replaced (chapter 7B).

Main faults in the selector mechanism

Chapter 7B describes the procedure for checking and adjusting the automatic transmission selector cable. The most common faults caused by a poorly adjusted selector are:

• a) Starting the engine in gears other than "Park" or "Neutral".
• b) Discrepancy between the indication of the engagement of any gear and the gear actually engaged.
• c) The vehicle is moving while the "Park" or "Neutral" mode is engaged.
• d) Unreliable or incorrect gear shifting.

Contact chapter 7B and adjust the selector cable.

The gear does not shift down when the accelerator pedal is fully depressed (kickdown)

• Low transmission fluid level (chapter 7B)
• Incorrect selector adjustment (chapter 7B).
• Throttle position sensor malfunction (chapter 4).

Engine does not start in any gear, or starts in gears other than Park or Neutral

• Incorrect adjustment of the selector cable (Chapter 7B)

Transmission slippage, rough shifting, noise or no rotation in forward or reverse gears

There are many possible causes for the above malfunctions, but the car owner can only do one thing - the fluid level. Before sending the car to a service station, check the level and condition of the fluid (see chapter 7B). Top up or replace fluid as needed. If you cannot fix the problem, contact a specialist.