Checking wiring from knock sensor to engine control unit — AUDI
Checking wiring from knock sensor to engine control unit on Audi: 7 steps, 1 torque figure, engines APF, AVU, BFQ.
Workshop procedure for AUDI — the exact step sequence and torque figures, straight from real workshop data.
🧭 Before you start
Fits: Audi A3 (8L, 1996–2003)
- Special tools named: V.A.G 1598/31
Don't miss
- Connect test box V.A.G 1598/31 to wiring harness for engine control unit. Do not connect to the engine control unit itself.
- To avoid accident risks when road testing the vehicle with test equipment, always observe the relevant safety precautions . — Interrogate the fault memory of the engine control unit again.
🔩 Torque settings
Values can differ between engine variants — check the code stamped on your block.
| Torque | Fastener / step |
|---|---|
| 20 Nm (15 lb-ft) | Loosen the knock sensor then tighten it |
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.
📐 19 workshop diagrams for APF
Real factory drawings for this job — timing marks, bolt locations and routing. Locked in the free view.
📋 Procedure
- Connect test box V.A.G 1598/31 to wiring harness for engine control unit. Do not connect to the engine control unit itself.
- Check for open circuit and short to positive or earth in the following wiring connections:
- Rectify any open/short circuit as necessary.
- Loosen the knock sensor then tighten it to 20 Nm. — 20 Nm (15 lb-ft)
- Perform test drive.
- ⚠ To avoid accident risks when road testing the vehicle with test equipment, always observe the relevant safety precautions . — Interrogate the fault memory of the engine control unit again.
- Replace the knock sensor G61.
Ask TorqFix about your Audi APF — it answers with the exact sequence for that engine and the workshop drawing for each step. First question is free after a 20-second sign-up, no card.
Ask about your Audi APF — free → or sign up free to see the drawingsOther AUDI procedures
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Who makes these pages, and how
TorqFix was built by a mechanic — after a 2,700 km drive with five roadside repairs that no diagnostic tool could explain.
The figures on this page come from manufacturer workshop documentation and are shown as they are. The page is assembled automatically from that data — it is not written by an AI. The AI works in the chat, where it answers for your specific car. It writes nothing here.
Variants of the same model differ. Cross-check torque against the factory manual for your engine before final tightening.
Seen a figure that does not match your manual? Write to us — we correct it and note when. support@torqfix.com
The story behind TorqFix →Workshop data on this page last updated 20 Sep 2026.