Volkswagen Golf Service & Repair Manual: Removing and installing engine control unit -J623- (with protective housing)

Hot air blower -VAS 1978/14A--item 1- with nozzle -2- from wiring harness repair set -VAS 1978 B-

If engine control unit is renewed, select test sequence/function Replace engine control unit on “vehicle diagnostic tester” in “Guided functions” mode.
Switch off ignition and remove ignition key.

Note

t	If the engine control unit comes into contact with the positive battery terminal, the engine control unit will be destroyed.

Therefore, the battery must be disconnected before the engine control unit is removed → Electrical system; Rep. gr.27.

Note Cover the area around the engine control unit, and protect it from flying sparks.

Make groove (for a screwdriver) in head of shear bolt -1- using a small grinder -2-.

Note

The threads of the shear bolts are secured with locking fluid. To unscrew these bolts, the threads must therefore be heated with the hot air blower.

Select settings on hot air blower as shown in illustration, i.e. set temperature potentiometer -2- to maximum heat output and two-stage air flow switch -3- to position 3.

Risk of damage to adjacent components caused by hot air blower. Risk of overheating.If necessary, cover adjacent components.

It is essential that the engine control unit -J623- be provided with the protective housing again.
Remove any locking compound residues from the threaded holes for the shear-head bolts. Threads can be cleaned using a tap (thread cutter).
Use new shear-head bolts.

After having installed the new engine control unit, the following work must be carried out:

Connect battery → Electrical system; Rep. gr.27.
Connect vehicle diagnostic tester.
Switch on ignition and select the following menu options on vehicle diagnostic tester:

Removing and installing engine control unit -J623- (with protective housing)