Engine Control Module: Service and Repair

Engine Control Module

Special tools, testers and auxiliary items required

• Heat gun - 1 - (from the wiring harness repair kit (VAS 1978))





• Nozzle attachment - 2 - (also from the wiring harness repair kit (VAS 1978))

• Commercially available locking pliers (vise grips) - 3 -

• Vehicle diagnostic, testing, and information system (VAS 5051B)

The engine control module - 1 - is connected with a metal retainer - 2 and 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 engine control module (e.g. to connect the test box or to replace the ECM), the protective housing must be removed.

Removing

- If engine control module was replaced, select diagnostic object "Replacing engine control module (ECM)" in "Guided Functions".

- Turn ignition and remove the ignition key.

- Pry off the caps on the wiper arms using a screwdriver.

- Loosen nuts - arrows - by several turns.





- Loosen wiper arms from the wiper axle by tilting slightly.

- Then, remove nuts completely and remove wiper arms from the wiper axles.

• If it is not possible to remove the windshield wiper arms this way, use the puller (T10369) or a commercially available puller.

- Remove rubber seal - 1 - and remove plenum chamber cover - 2 -.





• The plenum chamber cover could be damaged.

• Coat the transition area between the windshield and plenum chamber cover - 2 - with soapy water and carefully pull the cover vertically up out of the retainers on the windshield, beginning at the edge of the window.

- Remove plenum chamber cover - 2 - by carefully pulling cover out of retainer on windshield.

- Free up rear engine wiring harness on plenum chamber partition.

- Open clips - arrows - and remove ECM.





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.





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 the 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.





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 of shear bolts as shown in illustration.

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





- Remove shear bolts with suitable 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 connectors.

- Remove both retainer bolts from ECM.

- Disengage connector from ECM and remove connector.





- Remove used ECM and connect new one.

Installing

Install in reverse order of removal.

- After that, the ECM 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.

After installing new Engine Control Module, the following work steps must be performed:

- Activate the engine control module in the "Guided Functions" operating mode under "Replace engine control module" on the vehicle diagnosis and service system (VAS 5052).