Engine Control Module: Service and Repair

Engine Control Module (J623)

• Some Engine Control Modules (ECM) (J623) are not equipped with a protective housing. The removal and installation of the protective housing depends on the engine and transmission combination.

• The ECM - 1 - has a protective housing - 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 ECM (for example to connect the test box or to replace the ECM), the protective housing must be removed.

In case the protective housing has been installed, use the following special tools:

Special tools, testers and auxiliary items required

• Hot Air Blower (VAS 1978/14A) with nozzle attachment from the Wiring Harness Repair Kit (VAS 1978 B)

• Small commercially available locking pliers

Removing

- Select "replace engine control module" in "Guided Functions" on the vehicle diagnostic tester if the ECM was replaced.

- Turn off the ignition and remove the key.

- Remove the plenum chamber cover.

- Remove the bolts - arrows -, pull the filler tube out of the windshield washer fluid reservoir and out of the opening in the body and move it to the right.






- Open the retainer - arrow - and remove the ECM - 1 -.






• Ignore - 2 -.

Additional steps if there is a protective housing installed.

The ECM - 1 - is secured in a protective housing - 5 - with retaining tabs - 2 - and shear bolts - 3 and 4 - to make it harder to access it.






The shear bolts threads - 4 - (that are not installed in 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 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 airflow 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.

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






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

- The shear bolts installed in the Engine Control Module (ECM) do not need to be heated for removal. They can be removed without heat.






- Separate the protective housing from the control module connectors.

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

- Remove old ECM and install the ECM.

Installing

Install in reverse order of removal.

- If protective housing was installed, then the ECM must absolutely be retrofitted with the protective housing.

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

- Always use new shear bolts.

Perform the following step after installing a new ECM module.

- Activate the ECM in "Guided Functions" under "replace engine control module". To do this, use a vehicle diagnostic tester.