Engine Control Module: Service and Repair
Engine Control Module
Special tools, testers and auxiliary items required
• Hot air gun from Wiring Harness Repair Kit (VAS 1978A).
• Nozzle attachment from Wiring Harness Repair Kit (VAS 1978A)
• Small commercially available locking pliers
• Some engine control modules are not equipped with a protective housing. The removal and installation of the protective housing depends on the engine and transmission combination.
• 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.
• The protective housing must be removed to disconnect the connectors from the engine control module.
Removing
- If the engine control module is replaced, select "Guided Functions" on the Vehicle Diagnosis, Testing and Information System (VAS 5051B) and then "Replace engine control module".
- Turn the ignition and remove the ignition key.
- Remove rubber seal - 1 - for plenum chamber cover.
- Remove plenum chamber cover - 2 -.
- Pry out cover caps on windshield wiper arms with a screwdriver and loosen nuts - arrows - a few turns.
- Loosen wiper arms by tilting slightly from windshield wiper axle.
- Remove nuts completely and remove wiper arms.
• If wiper arms cannot be removed in this way, use a standard puller.
- Remove the bolts - arrows - and the cowl panel trim - 1 - from the windshield.
- If the vehicle is equipped with dome braces, remove bolts - 1 and 3 - and remove dome braces - 2 -.
- Remove the bolts - arrows - and the cover from the E-box.
CAUTION!
The heater pump valve unit to the left of the E-box becomes very hot during operation or when the ignition is on.
- Carefully pry off the retaining clip - 3 - with a screwdriver - arrows 1 and 2 - and remove the ECM from the E-box.
The engine control module - 1 - is secured in a metal housing - 5 - with retaining tabs - 2 - and shear bolts - 3 and 4 - to make it harder to access it.
• Some engine control modules are not equipped with a protective housing. A protective housing is not installed in vehicles with automatic transmissions.
The threads of the shear bolts - 4 - (that are not screwed into 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 screwed into 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 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.
Grinding and drilling is not permitted.
- Warm threads on connector-side shear bolts for approximately 25 to 30 seconds.
- Remove shear bolts with locking pliers (see direction of - arrow -).
- The shear bolts installed in the engine control module do not need to be heated for removal.
- Disconnect metal retainers from the ECM connectors.
- Disengage the connectors from the engine control module and disconnect the connector.
- Remove old Engine Control Module (ECM) (J623) and install the Engine Control Module (ECM) (J623).
Installing
Install in reverse order of removal.
- After that, the Engine Control Module (ECM) (J623) 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.
- Clip the cowl panel trim into the retainers on the windshield.
The procedures to follow after connecting the new ECM are described in Guided Fault-Finding and Guided Functions.