Scan Tool Connecting
Wiring and Components, Checking with Test Box VAG 1598/31
• The test box adapter cable (121-pin) (V.A.G 1598/31) is designed so that it can be connected simultaneously to the engine control module harness and the engine control module itself.
• This is advantageous because electronic engine control remains fully functional (e.g. measurement of signals with engine running) when the test box is attached.
• The procedures will indicate whether the engine control module is to remain connected to the test box or not.
• To connect testing devices to the test box (V.A.G 1598/31), always use adapters from connector test set (V.A.G 1594 C).
CAUTION!
To avoid damaging electronic components, switch to the corresponding measuring range and observe all test conditions before connecting the test leads.
Special tools, testers and auxiliary items required
• Heat gun - 1 - from wiring harness repair kit (VAS 1978)
• Nozzle attachment - 2 - also from wiring harness repair kit (VAS 1978)
• Small, commercially available locking pliers (vise grips)
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.
Work Procedure
- Switch off ignition.
- Remove rubber seal - 1 - for plenum chamber cover.
- Remove plenum chamber cover - 2 -.
- Pry off caps on wiper arms with a screwdriver and remove nuts.
- Pull wiper arms from wiper axles.
- Remove left and right bolt - arrows - from cowl panel trim - 1 -.
- Remove bolts - arrows - and remove cover form E-box.
CAUTION!
The heater pump valve unit (left of E-box) becomes very hot during operation - Risk of burning!
- Carefully pry off retaining clip - 3 - with a screwdriver - arrows 1 and 2 - and remove ECM from E-box.
To increase difficulty with which ECM connectors can be accessed, the ECM is secured in a metal housing with retaining tabs and shear bolts.
The threads of shear bolts - 1 - (that are not installed into the ECM) are coated with a locking compound. For this reason, threads must be heated with heat gun to remove both bolts.
The threads of both shear bolts - 2 -, that are installed 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 adjustment on heat gun as shown in the illustration, with temperature potentiometer - 2 - set to maximum heat and 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.
- Heat threads of both shear bolts - 1 - for approximately 25 to 30 seconds.
- Remove shear bolts with locking pliers.
- Both shear bolts that are installed into the ECM do not require heating to be removed. They can be removed without heat.
- Disconnect metal retainers from ECM connectors.
- Release and pull off connector from engine control module (ECM).
- Connect adapter cable (121-pin) (V.A.G 1598/31) to wiring harness connector. Ground (GND) clip at test box must be clipped to battery minus. The procedures will indicate whether engine control module is to be connected to test box.
- Perform test as described in relevant repair sequences.
Installing Engine Control Module (ECM) (J623)
Installation is in reverse order of removal.
- The ECM must be equipped with metal retainer again.
- New shear bolts must always be used.
- Clean threaded holes of residue and locking compound for new shear bolts. Cleaning can be performed with a thread cutter (tap).
- Check DTC memory and, if necessary, erase. => Vehicle diagnostic, testing, and information system VAS 5051