Removing and installing engine control unit J623 with protective housing, Golf, Passat — VW

🧭 Before you start

Fits: VW Golf VII Variant (BA), VW Golf VII (5G, 2012–2020), VW Passat B8 (3G, 2014–)

• Renewed: shear bolts

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• 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.

🔧 Engine codes this applies to

📋 Procedure

1. If the engine control unit is to be renewed, switch on ignition, and select the following menu options on vehicle diagnostic tester:
2. Switch off ignition and remove ignition key. [Note: If the engine control unit comes into contact with the positive battery terminal, the engine control unit will be destroyed. For this reason, the battery always needs to be disconnected prior to removing the engine control unit from its bracket Electrical system27Battery; Disconnecting and connecting battery.]
3. 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.]
4. 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.
5. Heat head of shear bolt (1) for approx. 20 to 30 seconds.

6. Unscrew shear bolt (1) using screwdriver (2).
7. Remove protective housing from engine control unit J623.
8. Release fastener (arrow A), and remove engine control unit J623(arrow B).
9. Release and unplug connectors for engine control unit J623.
10. Insert lower edge of engine control unit J623 into bracket (arrow A), and engage engine control unit in bracket at upper edge.
11. It is essential that the engine control unit J623 be provided with the protective housing again.
12. Clean the threaded holes for the shear bolts of thread-locking agent residues. Threads can be cleaned using a thread tap.
13. Always use new shear bolts.
14. Connect battery Electrical system27Battery; Disconnecting and connecting battery.
15. Switch on ignition and select the following menu options on vehicle diagnostic tester:

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