U0109

Lost Communication With Fuel Pump Control Module A

Q: Is it safe to drive with U0109?

Not really — losing communication with the fuel pump control module can cut fuel delivery, so the engine may stall or refuse to start; get it fixed before relying on the car.

Q: Can I just clear U0109?

You can, but if the module or its wiring is truly at fault the code returns and the engine may quit again; the connection has to be repaired.

Network / communication Generic OBD-II High

What it means

U0109 means the ECM has lost communication with the fuel pump control module — the controller that manages fuel pump operation and pressure. Without it the engine can lose fuel delivery, leading to hard starting, stalling, or a no-start. It is usually caused by a wiring or connector fault, a lost power or ground feed, or a failed module rather than the pump itself. Because it can leave you stranded, treat it as a priority repair.

High

Can I keep driving? Risky — if the fuel pump control module goes silent the engine can lose fuel delivery and stall or fail to start, so treat it as a possible no-start and repair promptly.

Real-world scan data

Seen in

103

scans in the past year

Found in

<0.1%

of scans

<0.1%

of scans that found faults

Figures reflect only diagnostic scans recorded through our own apps and tools. Cars are typically scanned because a symptom or warning light prompted it, so these counts describe our scan records — not the incidence of faults in any model, and not the quality, reliability, or safety of any vehicle. No comparison between manufacturers or models is implied. All trademarks belong to their respective owners; no affiliation or endorsement is implied.

Common symptoms

What you'll notice

Hard starting, extended cranking, or no-start
Engine stalling or cutting out while driving
Check-engine light on, sometimes with fuel-related codes
Fuel pump not priming when the key is turned on

Common causes

Most likely first

Blown fuse or lost power/ground feed to the fuel pump control moduleLikely
Damaged, corroded, or disconnected wiring or connector at the moduleCommon
Failed fuel pump control moduleCommon
CAN bus wiring fault between the module and the ECM/gatewayLess often
Water intrusion or corrosion at the module, often mounted near the tankLess often

How to diagnose & fix

Work through it in order

Scan for companion codes and check whether the module responds at all to a scan tool.
Confirm power and ground at the fuel pump control module and check its fuse.
Inspect the module's connector and CAN wiring for corrosion, damage, or water intrusion.
Check the bus circuits between the module and the ECM/gateway for opens or shorts.
If power, ground, and wiring are good but the module stays silent, replace it, then clear and re-test.

FAQ

Quick answers

Is it safe to drive with U0109?+

Not really — losing communication with the fuel pump control module can cut fuel delivery, so the engine may stall or refuse to start; get it fixed before relying on the car.

Can I just clear U0109?+

You can, but if the module or its wiring is truly at fault the code returns and the engine may quit again; the connection has to be repaired.

Read & clear U0109 yourself

Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.

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✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX