What it means
A control module has lost communication with the fuel pump control module. Fuel delivery may be affected on vehicles that use a separate control module for the pump.
How it works
The fuel pump control module regulates the pump on vehicles that use a separate module, often adjusting fuel delivery to meet engine demand. It reports status to other modules over the vehicle network. U0109 sets when a reporting module stops receiving expected messages from the fuel pump control module.
Common causes
Most likely first.
- Loss of module power or ground
- Open, shorted, or damaged communication wiring or connector
- Module or gateway fault
Symptoms
- Warning lights or messages
- Communication faults in other modules
- Starting or running problems may occur
How to diagnose it
- Scan all modules for U0109 and related fuel or network codes, and save freeze-frame data before clearing codes.
- Note whether the engine cranks, starts, stalls, or loses power, and check whether fuel pump module data is available.
- Inspect the fuel pump control module connector and harness for corrosion, loose pins, water intrusion, or damage.
- Check the module's power and ground circuits under the captured conditions against the manufacturer's specification.
- Test the communication wiring for opens, shorts, or poor connections using the vehicle wiring diagram.
- If supplies and network wiring are sound, use vehicle-specific diagnostics to distinguish a module fault from a gateway or pump circuit problem.
Common fixes
- Repair a loose or corroded fuel pump control module connector.
- Repair damaged wiring or a poor ground connection at the module.
- Restore module power and fix the cause of any blown fuse.
- Repair a gateway or network fault if testing identifies one.
- Replace or program the fuel pump control module only after its supplies, network, and pump circuits have been checked.
Can I keep driving?
If the engine starts and runs normally, limit driving and avoid situations where a sudden stall would be dangerous. If it hesitates, stalls, or will not start, do not continue driving; fuel delivery may be unreliable.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.