Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
12 51 001 Replacing Wiring Harness Section For Engine (S85)
Necessary preliminary tasks:
- Read out fault memory of control unit of Digital Motor Electronics (DME).
- Check stored fault messages.
- Switch off ignition.
- Disconnect battery.
- Remove intake air manifold. See 11 61 050 REMOVING AND INSTALLING AIR INTAKE MANIFOLD (S85) .
- Remove cover for ionic current control unit on left and right.
- Remove ignition coil cover on left and right.
- Unlock all plug connections in electronics box and disconnect.
Release bolt on cable duct (1).
Release bolt on cable duct (1).
| Work step | Note: |
|---|---|
| Release battery positive lead on cable duct at front and rear | Tightening torque. See ENGINE ELECTRICAL SYSTEM - TIGHTENING TORQUES . |
| Unlock plug on ignition coils on left and right and disconnect | |
| Unlock plug on ionic current control unit on left and right and disconnect | |
| Release grounding cable for ionic current control unit on left and right | |
| Unlock plug on pulse generator of left and right inlet camshafts and disconnect | |
| Unlock plug on pulse generator of left and right exhaust camshafts and disconnect | |
| Unlock plug on wiring harness section for alternator on cable duct and disconnect | |
| Unlock plug on wiring harness section for A/C compressor on cable duct and disconnect | |
| Unlock plug on fuel injectors on left and right and disconnect | |
| Unlock plug on electric switchover valve and disconnect | |
| Unlock plug on Hall sensor on left and disconnect | |
| Unlock plug on servomotor on left and disconnect | |
| Unlock plug on coolant temperature sensor and disconnect | |
| Unlock plug on idle speed actuator on left and right and disconnect | |
| Unlock plug on tank venting valve on left and right and disconnect | |
| Unlock control line on starter motor and disconnect | |
| Unlock plug on Hall sensor on right and disconnect | |
| Unlock plug on differential pressure sensor and disconnect. | |
| Unlock plug of crankshaft pulse generator and disconnect. | |
| Unlock plug on control sensor on left and right and disconnect | |
| Unlock plug on monitor sensor on left and right and disconnect | |
| Unlock plug on temperature sensor on left and right and disconnect |
Release bracket on underside of transmission.
Lay cable, plugs of oxygen sensors, temperature sensor and crankshaft sensor over bracket of right catalytic converter.
Feed out cable towards top.
Remove wiring harness.
Installation:
Pay attention to cable routing/mounting points.
Now clear the fault memory.
NO RELATED
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.