U0109 — Fuel pump control module communication lost
The vehicle's main computer cannot communicate with the fuel pump control module. This usually happens due to wiring issues, a faulty module, or network problems within the car's electronic system. Without this communication, the fuel pump may not operate correctly, potentially causing starting problems or engine stalling.
Common causes
The cause is almost always one of a few things. Here they are — U0109 rarely comes from anything outside this list:
- Damaged or corroded wiring/connectors to fuel pump module
- Faulty fuel pump control module
- Blown fuse or relay related to fuel pump circuit
- Network communication fault in vehicle CAN bus
- Software glitch in engine control unit
Where to start
In the order a sensible mechanic would work — the cheap checks first, the expensive replacements only after:
- Check and clean wiring connectors to fuel pump module
- Inspect and replace any blown fuses or faulty relays
- Test communication lines and repair damaged wiring
- Reflash or update engine control unit software if needed
- Replace fuel pump control module if all else fails
That is what holds for U0109 in general. From here it depends on your engine — tell me which car it is and what it does, and I will give you the steps for it: real procedures, torque figures and diagrams instead of general advice.
Why TorqFix for your car?
Above is what the code means and why it appears. TorqFix goes further — it gives you specific procedures, torque values, wiring diagrams and pinouts for your exact engine, not generic steps for every car. Real workshop data (127,000+ diagrams, 10,000+ procedures), interpreted by AI in your language.
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Code breakdown
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.
The same code can mean different things on different makes. Match the meaning to your make before acting on it.
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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