Knock sensor — removal and installation (BMW 3 Series E46)

4-cylinder engine M43TU

Removal

1. Two knock sensors are bolted to the left wall of the cylinder block. One sensor detects knock in cylinders 1 and 2, and the other in cylinders 3 and 4.

2. Relieve the pressure in the fuel system (see chapter 4A) and disconnect the negative battery cable.

3. Remove the upper section of the intake manifold (see chapter 4A).

4. Disconnect the electrical connectors of the camshaft and crankshaft position sensors.

5. Remove the two bolts securing the wire box to the lower section of the intake manifold.

6. Disconnect the electrical connector plug from the knock sensor and release the connector from the bracket.

7. The knock sensor for cylinders No.1 and 2, located between the oil filter and the intake manifold, can be removed as follows (Fig. 4.7).

• a) The sensor can be accessed from above through the opening between the intake manifold pipes of cylinders 2 and 3, if you first disconnect the fuel line from the fuel rail. Be prepared for fuel to leak from the connection. Plug both openings to prevent dirt from getting into the fuel system.
• b) To provide sufficient space for removing the sensor, you must first unscrew the cooling system pipe mounting bolt and pull the pipe away from the engine a little.
• c) Unscrew the sensor mounting bolt and remove the sensor from the engine.

8. Access to the second sensor is obvious. Simply unscrew the sensor mounting bolt and remove it from the engine (Fig. 4.8).

Installation

9. Before installing the sensor, thoroughly clean the mating surfaces of the cylinder block and the sensor itself.

10. Install the sensor in place and tighten its bolt to the required torque.

11. Otherwise, installation is carried out in the reverse order of removal, taking into account the following notes.

• a) Connect all electrical connectors.
• b) Install the upper section of the intake manifold as described in Chapter 4A.
• c) Fill the fuel system as specified in section 4A.

4-cylinder engine N42

Removal

12. Disconnect the negative battery cable.

13. Remove the intake manifold as described in Chapter 4A.

14. There are two knock sensors installed on the engine. The rear sensor is blocked from access by the starter. If you need to remove the rear sensor, you must first remove the starter (Fig. 4.14).



15. Trace the sensor wiring and disconnect their electrical connectors.



16. Unscrew the bolts and remove the sensors (Fig. 4.16).

Installation

17. Install the sensor in the reverse order of removal. Before installation, thoroughly clean the mating surfaces of the sensor and the cylinder block. Tighten the sensor mounting bolt to the required torque.

6-cylinder engines

Removal

18. These engines have two knock sensors on the left wall of the cylinder block. One sensor monitors knock in cylinders 1 through 3, the other in cylinders 4 through 6.

19. Disconnect the negative battery cable.

20. Remove the intake manifold (see chapter 4A).

21. Locate the sensor electrical connector bracket located under the idle air control valve.

Caution! If you need to remove both sensors, mark the connectors so that you can connect them correctly during installation. Incorrect connection of the connectors can result in serious engine damage.

22. Release the connector from the retainer and disconnect it(them).

23. Loosen the sensor mounting bolt and remove the sensor from the engine. The knock sensor for cylinders 1-3 is located under the temperature sensors in the cylinder head (Fig. 4.23). The sensor for cylinders 4-6 is located behind the connector bracket.

Installation

24. Before installing the sensor, thoroughly clean the mating surfaces of the cylinder block and the sensor itself.

25. Install the sensor in place and tighten its bolt to the required torque.

26. Connect the sensor connectors and secure them to the bracket. Do not mix up the connectors.

Warning! Incorrect connection of connectors may result in serious engine damage.

27. Install the intake manifold (see chapter 4A).

(The original article is located on: «bmwman.ru»)