Engine Control Module: Service and Repair

Engine Control Module (J623)

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

Special tools, testers and auxiliary items required

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

• Puller (T10369)

• Small Commercially Available Locking Pliers

• Some ECMs 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 - 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 (for example to connect the test box or to replace the ECM), the protective housing must be removed.

Removing

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

- Turn off the ignition and remove the key.

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

- Loosen the nuts - arrows - by several turns.






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

- Remove the nuts and remove the windshield wiper arms from the wiper axles.

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

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






• Danger of causing damage to the plenum chamber cover.

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

- Free up the engine wiring harness on the back of the plenum chamber bulkhead.

- Open clips - arrows - and remove the ECM.






Additional steps if there is a protective housing installed.

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 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 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.

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






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






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

- Disconnect metal retainers from the connectors.

- Remove both retainer bolts from ECM.

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






- Remove the used ECM and connect the new ECM.

Installing the ECM

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.

Perform the following step after installing a new ECM

- Activate the ECM in "Guided Functions" under "replace engine control module". Use a vehicle diagnosis tester for this.