Removing and installing engine control unit J623, engine control unit with metal locking plate — VW

🧭 Before you start

Fits: VW Passat B8 (3G, 2014–)

• Renewed: shear bolts

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• If the engine control unit J623 is renewed, the adaption values must be read out and stored before the engine control unit J623 is removed.
• If the adaption values of the injectors cannot be read from the old (defective) engine control unit anymore, the adaption values must be entered manually into the new engine control unit.
• The threads of the shear-head bolts are secured with locking fluid. To unscrew these bolts, the threads must therefore be heated with the hot air blower.
• The metal locking plate must always be re-fitted on the engine control unit J623.

🔧 Engine codes this applies to

📋 Procedure

1. If the engine control unit J623 is renewed, the adaption values must be read out and stored before the engine control unit J623 is removed.
2. The procedure is described in "“Guided Functions”" mode, test sequence/function "“Replace engine control unit”". Use Fahrzeugdiagnosetester for this.
3. Save adaption values in a file.
4. After you have saved the adaption value file, switch off ignition and remove ignition key, [Note: If the adaption values of the injectors cannot be read from the old (defective) engine control unit anymore, the adaption values must be entered manually into the new engine control unit.]
5. ⚠ 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. — Open retaining clip (arrow) and take out engine control unit J623.

6. Make groove (for a screwdriver) in head of shear-head bolt (1) using a small grinder (2). [Note: The threads of the shear-head bolts are secured with locking fluid. To unscrew these bolts, the threads must therefore be heated with the hot air blower.]
7. Select settings on hot air blower as shown in figure, i.e. set temperature potentiometer (2) to maximum heat output and two-stage air flow switch (3) to position 3.
8. ⚠ Risk of burns from hot air blower.When heating up the thread of the locking element, the shear-head bolts and parts of the sheet-metal housing become hot as well. Ensure to only heat up the thread and no surrounding components. Cover surrounding components, if necessary. — Hold hot air blowerVAS 1978/14A with nozzle attachment (arrow) to thread of shear-head bolt and heat thread for about 20 to 30 seconds.
9. Unscrew shear-head bolt (1) using screwdriver (2).
10. Detach metal locking plate from connectors for engine control unit J623.
11. Release and unplug connectors.
12. The metal locking plate must always be re-fitted on the engine control unit J623.
13. Remove any locking compound residues from the threaded holes for the shear-head bolts. Threads can be cleaned using a tap (thread cutter).
14. Always use new shear bolts.
15. Use to activate engine control unit.

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