Removing and installing high-voltage wiring harness for high-voltage battery — AUDI

🧭 Before you start

The system is de-energised and secured by a high-voltage technician first. Access is from three places: the engine bay (headlight, upper longitudinal member, JX1 cover), underneath (trim panels, spare wheel well covers, fuel tank, refrigerant line brackets) and the luggage compartment (floor trim, tool kit, wiring junction TV1). The harness is unplugged at both ends and lowered out through the floor opening. Refitting reverses this, with the cable ties and leadthrough restored exactly.

Fits: Audi A8 D4 (4H, 2010–2017)

Don't miss

• Only a qualified high-voltage technician may de-energise the system, using the diagnostic tester, and lock it with cap T40262.
• Unplug high-voltage connectors by pulling straight upwards; levering, rotating or tilting damages the coding on the wires.
• Check the red warning label on JX1 is present and leave it undamaged.
• Pull out the pilot line connector first, then fold up the retaining clip at the battery terminals.
• Refit every cut or released cable tie in its original position and make sure the floor leadthrough engages and seals.
• Never lean on or kink high-voltage cables; insulation damage is not always visible afterwards.

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

🔧 Engine codes this applies to

🔩 Torque settings

Values can differ between engine variants — check the code stamped on your block.

ℹ️ Always cross-check the exact figure against your vehicle's factory manual before final tightening — a wrong torque can damage the engine. These values are extracted from workshop data and may not cover every variant or revision.

📋 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. — Disconnect 12 V batteries Electrical system27Battery; Disconnecting and connecting battery.
3. Remove front left headlight Electrical system94Headlights; Removing and installing headlights.
4. Remove upper longitudinal member General body repairs, exterior50Lock carrier; Exploded view - lock carrier.
5. Unplug connector to bonnet lock (left-side) above cover of power and control electronics for electric driveJX1.

6. Unplug electrical connector (2).
7. Remove bolt (3) and move coolant expansion tank to one side. Coolant lines (1) and (4) remain connected.
8. Remove bolts (arrows) on cover (1) and take cover off power and control electronics for electric driveJX1(2).
9. Check that the red warning label on the power and control electronics for electric driveJX1 is present and take care not to damage it.
10. Push locking mechanism (4) in direction of (arrow).
11. Disconnect high-voltage wiring harness for hybrid batteryPX1(2) from power and control electronics for electric driveJX1 as described below.
12. Use release tool T40258 to release and unplug the high-voltage connectors for the high-voltage wiring harness for hybrid batteryPX1 from the left side.
13. ⚠ 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. — Release wiring bracket for high-voltage wiring harness for hybrid batteryPX1 in engine compartment and guide high-voltage wiring harness for hybrid batteryPX1 downwards out of engine compartment.
14. Remove underbody trim panels (front, centre & rear) on left side General body repairs, exterior66Underbody trim panels; Exploded view - underbody trim panels.
15. Remove covers (front and rear) for spare wheel well General body repairs, exterior66Underbody trim panels; Exploded view - covers.
16. Remove fuel tank with attached components Fuel supply system, petrol engines20Fuel tank; Removing and installing fuel tank.
17. Remove nuts (1) on brackets (2) for refrigerant lines.
18. Cut through cable ties towards rear as far as wiring guide (3) and unclip high-voltage wiring harness.
19. Remove nut (4) on wiring guide (3).
20. Unclip wiring guide (3) from floor (arrows).
21. Move refrigerant lines clear (1) at brackets (2).
22. Remove bolts (1) (2 Nm). — 2 Nm (1.5 lb-ft)
23. Unclip line (2).
24. Unclip wiring guide (3) from body (arrows).
25. Unscrew nuts (2) (2 Nm) on leadthrough (3). — 2 Nm (1.5 lb-ft)
26. Remove luggage compartment floor trim (right-side) General body repairs, interior70Luggage compartment trim panels; Removing and installing luggage compartment floor.
27. Remove centre and right sections of vehicle tool kit.
28. Remove wiring junctionTV1Electrical system97Relay carriers, fuse carriers, electronic boxes; Overview of fitting locations - relay carriers, fuse carriers, electronic boxes.
29. Unclip cover (1) over connectors of high-voltage wire for hybrid battery, positive terminal P1.
30. 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).
31. First pull out pilot line connector 1TV44(1) then fold up retaining clip (4) in direction of (arrow).
32. 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.
33. ⚠ 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. — Remove wiring guide (1) (1.5 Nm) and cut though cable ties (arrows). — 1.5 Nm (1.1 lb-ft)
34. Unclip leadthrough (3) and guide downwards through body floor.
35. Guide high-voltage wiring harness for hybrid batteryPX1(2) through opening in body floor and take out of vehicle downwards. [Note: All cable ties which have been released or cut through during removal must be re-attached in the same position on installation.Tighten all screw connections to the tightening torques specified.When installing leadthrough in luggage compartment floor, make sure that it engages and seals securely.]
36. ⚠ 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. — 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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