Engine Control Module: Service and Repair

Engine Control Module (J623)

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)

• Commercially available pliers

• Some Engine Control Modules (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 - 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.






• The protective housing must be removed to disconnect the connectors from the ECM.

Removing

- If the ECM was replaced, select diagnostic object "Replacing engine control module " in "Guided Functions" using a vehicle diagnostic tester.

- 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 the wiper arm cannot be removed in this way, use a standard puller.

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






- Open the clamp - arrow - and remove the ECM.






• Cover painted surfaces with a cloth to protect against scratches.

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 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 the connector side of the 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 -).






- 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 bolts from the 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.

- The ECM must be installed with a 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 engine control module:

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