Removing and installing high-voltage battery: Audi A8 D4 (CHJA)

🧭 Before you start

Have the system de-energised and locked out, remove the right-hand luggage floor trim and check the warning labels. Unplug the cooling module, release the high-voltage positive and negative cables after pulling the pilot line, disconnect the vent line, remove brackets and couplings and the potential equalisation line. Lift the unit onto rails, then out with a second person and store it under the correct warning notice. Refit in reverse with clean equalisation contacts and re-energise via the diagnostic tester.

Fits: Audi A8 D4 (4H, 2010–2017)

• Special tools named: VAS 6786

Don't miss

• Only a qualified high-voltage technician may de-energise and lock out the system.
• Pull the pilot line connector first, then release the high-voltage plugs with the release tool.
• Never lever high-voltage connectors or kink high-voltage wiring.
• Clean potential equalisation contact surfaces to bare, rust- and grease-free metal.
• Make sure no lines or connectors are trapped beneath the battery unit.

Written for this job from the workshop steps below · TorqFix editorial.

🔧 Engine codes this applies to

📋 Procedure

1. ⚠ Working on vehicles with high-voltage wiring:Do not support yourself or tools on high-voltage wiring or associated components --> this can damage the insulation. High-voltage wiring must not be excessively bent or kinked --> this can damage the insulation. The round high-voltage connectors are colour-coded with an external coloured ring and are provided with mechanical coding or guide lugs. It is important to observe this coding when joining up the round high-voltage connectors, otherwise the connectors can be damaged. — De-energise high-voltage system. [Note: De-energising high-voltage system:Connect vehicle diagnostic testerSelect Guided Fault Finding modeUsing the Go to button, select the following menu options in succession:Selecting function/componentBodyElectrical systemSelf-diagnosis-compatible systems8C - Hybrid battery management -J8408C - Hybrid battery management, functions51 - De-energise high-voltage system (Rep. gr. 93)]
2. ⚠ High voltage can cause fatal injuryDanger of severe or fatal injuries from electric shock The high-voltage system may only be de-energised by a suitably qualified person (Audi high-voltage technician). It must be definitely confirmed that the high-voltage system is de-energised. The system may only be de-energised using the vehicle diagnostic tester via "“Guided Fault Finding”". The qualified person (Audi high-voltage technician) confirms that the system is de-energised and uses the locking cap T40262 to ensure that the system cannot be re-energised. The ignition key and the maintenance connector for high-voltage system TW are then stored in a safe place by the qualified person.The qualified person (Audi high-voltage technician) marks the vehicle by attaching the appropriate warning signs. — Remove luggage compartment floor trim (right-side) General body repairs, interior70Luggage compartment trim panels; Removing and installing luggage compartment floor.
3. Check that the red warning label and the battery warning label are present on the hybrid battery unitAX1 and that they do not become damaged.
4. Unplug connectors (1) to battery cooling module.
5. Unclip cover (1) over connectors of high-voltage wire for hybrid battery, positive terminal P1.

6. Release and unplug connectors for high-voltage wire for hybrid battery, positive terminal P1(3) and high-voltage wire for hybrid battery, negative terminal P2(2).
7. First pull out pilot line connector 1TV44(1) then fold up retaining clip (4) in direction of (arrow).
8. Release and disconnect high-voltage wire for hybrid battery, positive terminal P1(3) and high-voltage wire for hybrid battery, negative terminal P2(2) using release tool T40258.
9. ⚠ Do not use excessive force when releasing and unplugging the high-voltage connectors.To release the catch, first press gently on the high-voltage connector you wish to unplug and then pull the connector upwards.Never use levering tools to release and unplug the high-voltage connectors.Only unplug high-voltage connectors by pulling them upwards. Do NOT rotate or tilt them; this could damage the coding on the high-voltage wires. — Pull off wiring guide (2) and wiring clip (arrow) and move high-voltage wiring harness for hybrid batteryPX1(1) to side.
10. Disconnect vent line (1) on hybrid battery unitAX1 and set down on hybrid battery unitAX1.
11. Remove brackets for fastening rings (1) on both sides.
12. Unscrew bolts (arrows) and remove bracket (1) upwards.
13. Remove couplings (1) on left and right.
14. Unscrew bolts (arrows) and remove coupling (1) upwards.
15. Unbolt potential equalisation line on body and set down on hybrid battery unitAX1.
16. Re-install luggage compartment floor trim (right-side) General body repairs, interior70Luggage compartment trim panels; Removing and installing luggage compartment floor.
17. Remove bolts (arrows) on bracket for hybrid battery unitAX1(1).
18. Place rails T40275(2) in luggage compartment on both sides.
19. Lift hybrid battery unitAX1 with bracket (1) over two bolt heads (arrows) and set down towards rear on rails (2).
20. With assistance from a second mechanic, take hold of the hybrid battery unitAX1(1) on both sides (arrows) and lift it out of luggage compartment.
21. Remove potential equalisation line on hybrid battery unitAX1.
22. Set down hybrid battery unitAX1 on a suitable surface.
23. Remove bolts (arrows).
24. Remove cover (1) from hybrid battery unitAX1.
25. Remove air ducts (1)(arrows).
26. Remove vent line from hybrid battery unitAX1.
27. Remove bolts (arrows) and take hybrid battery unitAX1(1) off bracket (2).
28. Set down hybrid battery unitAX1 on a suitable surface.
29. Put up battery warning notice (storage)VAS 6786 according to regulations. [Note: When fitting hybrid battery unitAX1 in vehicle, make sure that no lines or connectors are trapped beneath hybrid battery unitAX1.Check the contact surfaces of the potential equalisation lines prior to installation.The contact surfaces must be clean and free from rust and grease.Otherwise, repair the contact surfaces using the contact surface cleaning setVAS 6410Electrical system; General information97Cleaning contact surfaces.]
30. ⚠ Working on vehicles with high-voltage wiring:Do not support yourself or tools on high-voltage wiring or associated components --> this can damage the insulation. High-voltage wiring must not be excessively bent or kinked --> this can damage the insulation. The round high-voltage connectors are colour-coded with an external coloured ring and are provided with mechanical coding or guide lugs. It is important to observe this coding when joining up the round high-voltage connectors, otherwise the connectors can be damaged. — Connect high-voltage wires according to their coding .
31. Check that the red warning label and the battery warning label are present on the hybrid battery unitAX1 and that they do not become damaged.
32. Re-energise high-voltage system. [Note: Re-energising high-voltage system:Connect vehicle diagnostic testerSelect Guided Fault Finding modeUsing the Go to button, select the following menu options in succession:Selecting function/componentBodyElectrical systemSelf-diagnosis-compatible systems8C - Hybrid battery management -J8408C - Hybrid battery management, functions51 - Re-energise high-voltage system (Rep. gr. 93)]

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