Checking operation of fuel shut-off valve N109: Audi A3
Step-by-step checking operation of fuel shut-off valve N109 for the Audi A3: 8 steps. What to remove, in what order, and what to check after.
Checking the fuel shut-off valve N109 on the Audi A3 (8P, 2003–2012) with auxiliary heater is a pressure test combined with final control diagnosis. The fuel pipe to the auxiliary heater is detached and sealed or held over a container, and vacuum hand pump VAS 6213 is connected to it. The diagnostic tester is plugged into the 16-pin connector with the ignition off. About 1.5 bar is built up in the pipe and must hold for around 1 minute, which proves the valve closes. N109 is then activated through the auxiliary heater final control diagnosis, and the pressure must drop as soon as it opens. A pipe end left unsealed or a slow leak at the pump hose will give a misleading result.
🧭 Before you start
Detach the fuel pipe from the auxiliary heater and seal or catch its end, connect the hand pump and connect the tester to the 16-pin socket with the ignition off. Build up about 1.5 bar and confirm it holds for about 1 minute. Start final control diagnosis for the auxiliary heater, activate N109 and watch the gauge: the pressure must release as the valve opens. Reconnect the fuel pipe afterwards.
Fits: Audi A3 (8P, 2003–2012)
Don't miss
- Seal the detached fuel pipe or place it in a container to catch fuel.
- Connect the tester with the ignition switched off.
- Pressure of about 1.5 bar must hold for about 1 minute with the valve closed.
- Pressure must release immediately when N109 is activated.
- Keep ignition sources away from the open fuel pipe (general practice).
Written for this job from the workshop steps below · TorqFix editorial.
📋 Procedure
- Detach fuel pipe from auxiliary heater . [Note: Seal the fuel pipe detached or place the end of the detached fuel pipe in a small vessel (a small amount of fuel may emerge during subsequent final control diagnosis).]
- Connect e.g. vacuum hand pumpVAS 6213 to fuel pipe to auxiliary heater (A).
- With ignition switched off, connect vehicle diagnostic, testing and information systemVAS 5051 A to 16-pin diagnostic socket in vehicle using diagnosis cableVAS 5051/5A and select function "“Final control diagnosis of auxiliary/additional heater”"Guided Fault Finding function of vehicle diagnostic, testing and information system5051 A.
- Use the vacuum hand pumpVAS 6213 to build up a pressure of approx. 1.5 bar in the fuel pipe to the auxiliary heater.
- Wait approx. 1 minute. The pressure must be maintained.
- Perform final control diagnosis for auxiliary/additional heater Guided Fault Finding function of vehicle diagnostic, testing and information system5051 A. When doing so, keep switching until control element fuel shut-off valve N109 is displayed.
- Activate the fuel shut-off valve N109 control element and in doing so observe the display on the pressure gauge of the vacuum hand pumpVAS 6213.
- As soon as the fuel shut-off valve N109 is activated, the pressure in the fuel pipe must be released (via the fuel shut-off valve N109).
Other AUDI procedures
- Removing and installing toothed belt – Audi · 56 torque figures
- Removing engine – Audi A8 D3 · 41 torque figures
- Removing camshaft timing chain from camshafts – Audi A6/A7 C7 · 38 torque figures
- Installing engine – Audi A8 D4 · 36 torque figures
- Removing and installing camshaft timing chain · 29 torque figures
- Removing heat exchanger of rear air conditioning unit from air conditioning unit and re-installing
- Servicing automatic gearbox 01L, four-wheel drive — Removing and installing selector shaft
- Removing and installing printed circuits for mechatronic unit
- Removing and installing motor plate (rear) and cable for sunroof sun blind · 1 torque figures
- Exploded view - sump (top section) · 2 torque figures
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.