Engine Control Module: Service and Repair

Engine Control Module

Special tools, testers and auxiliary items required

• Heat Gun 220 V/50 Hz (VAS 1978/14) with nozzle attachment from Wiring Harness Repair kit (VAS 1978A)

• Locking Pliers (commercially available)

• 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.





• 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 the engine control module is replaced, in "Guided Fault Finding" select "Replace Engine Control Module" to (VAS 5051B).

- Turn the ignition and remove the ignition key.

- Remove front rubber seal on plenum chamber.

- Unclip the right plenum chamber cover and lift it up slightly.

- Grasp under plenum chamber cover and unclip ECM - 1 - from bracket.





• Ignore - 2 -.

To avoid damage (burning) of wire connections and harness connectors, insulation and control modules, the following work steps must be adhered to exactly! Observe operating instructions for heat gun.

- 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".





• Next, the thread of protective housing in which the shear bolts is threaded in is heated using the heat gun. This step decreases the locking effect of the locking compound on the thread of the shear bolts, thus allowing the shear bolts to be unscrewed more easily.

By heating the shear bolts, parts of the protective housing are heated intensely. Do not burn yourself on this! Make sure that only the shear bolt is heated if possible and no other components in the vicinity are heated. Possibly cover these parts.

- Perform the following work steps in order on both shear bolts - 4 -.





- Guide nozzle of hot air gun on to shear bolt of protective housing.





- Switch the heat gun on and heat the bolt for approximately 20 to 25 seconds.

- Remove shear bolts with locking pliers in direction of - arrow -.





• 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).





- Remove both shear bolts - 3 -.

- Separate the retaining tab - 2 - of the control module connector.

- Release connector and disconnect multi-pin connectors from ECM.

• When multi-pin connector is disconnected from the ECM, adaptation values are erased and content of DTC memory remains intact.

Installing

Installation is in reverse order of removal, note the following:

- The ECM must be equipped with the protective housing again.

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

- Use new shear bolts.

After installing a new ECM, 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 (VAS 5051B).