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Checking secondary air inlet valve N112: VW Golf IV / Bora (AEH, AKL, APF, APK, …)

Step-by-step checking secondary air inlet valve N112 for the VW Golf IV / Bora: 11 steps. What to remove, in what order, and what to check after.

Workshop procedure for VW — the exact step sequence and torque figures, straight from real workshop data.

11 steps 12 engine codes engine codes merged from 4 documented variants

🧭 Before you start

Fits: VW Golf IV / Bora (1J)

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  • Start engine and run at idling speed. When the secondary air pump motor V101 runs, a vacuum must be perceptible at the union of the secondary air inlet valve N112.
  • Pull 2-pin connector off valve and connect voltage testerV.A.G 1527B to disconnected connector. Check activation whilst secondary air pump motor V101 is running: LED must light up.
  • Connect voltage testerV.A.G 1527B to contact 1 of disconnected connector and to earth: LED must light up.

🔧 Engine codes this applies to

AEHAKLAPFAPKAQYAZHBGPBGQBPRBPSCBTACBUA

📋 Procedure

  1. Pull upper vacuum hose (arrow) off secondary air inlet valve N112.
  2. Start engine and run at idling speed. When the secondary air pump motor V101 runs, a vacuum must be perceptible at the union of the secondary air inlet valve N112.
  3. Check activation of valve:
  4. Pull 2-pin connector off valve and connect voltage testerV.A.G 1527B to disconnected connector. Check activation whilst secondary air pump motor V101 is running: LED must light up.
  5. Renew secondary air inlet valve N112.
AEH? Steps differ between engine variants — check this job against your exact car before you commit to it. Check my car — free →
  1. Connect voltage testerV.A.G 1527B to contact 1 of disconnected connector and to earth: LED must light up.
  2. Check wire between 2-pin connector contact 1 and fuse 43 for open circuit referring to current flow diagram. Wire resistance: max. 1.5 Ω.
  3. Connect 121-pin adapter cableV.A.G 1598/31 to control unit wiring harness. The engine control unit remains disconnected.
  4. Check wire between test box socket 71 and 2-pin connector contact 2 for open circuit referring to current flow diagram. Wire resistance: max. 1.5 Ω.
  5. Additionally check wire for short circuit to battery positive and earth. Specification: ∞ Ω.
  6. Renew engine control unit 24.

Other VW procedures

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

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Workshop data on this page last updated 20 Sep 2026.