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) - 1 - with nozzle attachment - 2 - from Wiring Harness Repair kit (VAS 1978A)

• Locking pliers - 3 - (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 Engine Control Module (ECM) (e.g. to connect the test box or to replace the ECM), the protective housing must be removed.

Removing

- If Engine Control Module (ECM) is replaced, select diagnostic object "Replace ECM" in "Guided Functions" operating mode -> vehicle diagnostic tester.

- Switch off ignition and remove ignition key.

- Remove rubber seal at front of plenum chamber.

- Unclip right plenum chamber cover and raise slightly.

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





• Ignore - 2 -.

Risk of damage (burning) from wiring and connectors, insulation and control modules.

• Follow the next steps exactly! Observe hot air gun operating instructions.

- Perform adjustments on hot air gun as shown in illustration:

- Set temperature adjuster potentiometer - 2 - to maximum heat output.





- Set two-stage air quantity switch - 3 - to "3" position.

• 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 installed more easily.

Risk of burning.

• By heating the shear bolts, parts of the protective housing are heated intensely. Ensure as much as possible that only the shear bolt is heated and not the adjacent parts. Possibly cover these parts.

- Perform the following steps one after another on both shear bolts - 4 -.





- Direct hot air gun nozzle toward protective housing shear bolt.





- Switch hot air gun on and warm bolt for 20 to 25 seconds.

- Remove shear bolts with pliers - arrow -.





• 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).





- Remove both shear bolts - 3 -.

- Disconnect control module connector locking mechanism.

- Release connector and disconnect multi-pin connector from control module.

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

Installing

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

• Replace shear bolts.

- Reinstall ECM protective housing.

- Clean shear bolt threaded holds of locking compound residue using a thread tap, for example.

After installing a new Engine Control Module (ECM), the following work steps must be performed:

- Activate ECM in "Guided Functions" operating mode under "Replace Engine Control Module (ECM)".