Engine Control Module: Service and Repair

Engine Control Module

Special tools, testers and auxiliary items required

• Heat gun 220 V/50 Hz (VAS 1978/14) with nozzle attachment from wiring harness repair kit (VAS 1978)

• Small, commercially available locking pliers (vise grips)

• The Engine Control Module (ECM) - 1 - is bolted to a protective housing - 5 -. To make removing the shear bolts - 4 - for the retaining tabs - 2 - more difficult, the threads are coated with locking compound.





• To disconnect the connectors from the ECM (e.g. to connect the test box or to replace the ECM), the metal housing must be removed.

Removing

- If the engine control module is replaced, in "Guided Fault Finding" select "Replace Engine Control Module" to Vehicle Diagnosis, Testing and Information System (VAS 5051B).

- Turn ignition and remove the ignition key.

- Remove nut - 3 - and bolt - 2 -.





- Remove filler neck - 1 - with filler tube from the washer fluid reservoir and opening in the body - arrow -.

- Remove bolts - arrows - and the cover from the E-box.





- Release retainers - A arrows - and remove engine control module (ECM) (J623) - arrow B -.





To increase the difficulty with which the ECM connectors can be accessed, the ECM - 1 - is secured in a metal housing - 5 - with retaining tabs - 2 - and shear bolts - 3 and 4 -.





The threads of the shear bolts - 4 - (that are not screwed into the ECM) are coated with a locking compound. For this reason, the threads must be heated with the heat gun to remove both bolts.

The threads of both shear bolts - 3 -, that are screwed into the ECM, are not coated with a locking compound. The threads in the ECM housing must not be heated and do not require to be heated (unintentional heating of the ECM).





- Set the adjustment on the heat gun as shown in the illustration, with the temperature potentiometer - 2 - set to maximum heat and the two-stage air flow switch - 3 - set to level 3.






By heating the threads, the retaining tabs, shear bolts and parts of the metal housing become very hot. Do not burn yourself on this! Make sure that only the threads are heated as much as possible, and not any of the surrounding parts. Possibly cover these parts.

- Warm threads on connector-side shear bolts for approximately 25 to 30 seconds.





- Remove shear bolts with locking pliers (see direction of - arrow -).





- Both shear bolts that are screwed into the ECM do not require heating to be removed. They can be removed without heat.

- Disconnect metal retainers from the ECM connectors.

- Disengage connectors from ECM and then disconnect the connectors.

- Remove old engine control module (ECM) (J623) and install the engine control module (ECM) (J623).

Installing

Install in reverse order of removal.

- After that, the Engine Control Module (ECM) (J623) must be equipped with the metal retainer.

- Clean threaded holes for shear bolts of locking compound residue. Cleaning can be performed with a thread cutter (tap).

- Always use new shear bolts.

• Tightening Specifications E-box cover bolts: 3.5 Nm 3.5 Nm

Perform the following step after installing a new engine control module:

- Activate the engine control module in the "Guided Functions" operating mode under "Replace engine control module" on the vehicle diagnosis and service system (VAS 5051B).