Engine Control Module: Service and Repair

Engine Control Module

Special tools, testers and auxiliary items required

• Hot air gun (VAS 1978/14) - 1 - with nozzle attachment - 2 - from the wiring harness repair kit (VAS 1978A)





• Locking pliers - 3 - (commercially available)

• 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 electrical connectors from the ECM (for example, to connect the test box or to replace the ECM), the protective housing must be removed.

Removing

- If the ECM s replaced, in "Guided Fault Finding" select "Replace Engine Control Module" to vehicle diagnosis, testing and information system (VAS 5051B).

- Turn the ignition and remove the ignition key.

- Remove right cover from the plenum chamber.

- Remove the ECM by removing the bolts - arrows -.





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

Remove the ECM.





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





The threads of both shear bolts - 3 - (that are installed in 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.





CAUTION!
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.

Heat threads on the connector side of the shear bolts as shown in the illustration.

Switch on the heat gun and heat the bolt for approximately 20 to 30 seconds.





- Remove the shear bolts using locking pliers in the - direction of the arrow -.





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

- Disconnect the metal retainers from the electrical connectors.

- Remove both bolts from the ECM.

- Disengage the connectors from the ECM and disconnect the connector.

- Remove the old ECM and connect the new one.

Installing

Install in reverse order of removal.

- After that, the ECM must be equipped with the metal retainer.

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

- Always use new shear bolts.

- Carefully clip the cowl panel trim back into the retainer on the windshield.

The procedures to follow after connecting the new ECM are described in Guided Fault Finding and Guided Functions.