U0109
Lost Communication with Fuel Pump Control Module
The Fuel Pump Control Module has stopped transmitting on the vehicle data bus, so other control units no longer receive its messages. Fuel-delivery control is lost, which can starve the engine of fuel. Typical causes are loss of power or ground at the module, an open or shorted CAN/LIN bus wire, a connector fault, or an internal module failure.
- Check engine light: Yes
- Emissions related: Yes
- Repair difficulty: hard
Symptoms
- Multiple warning lights may illuminate
- Affected modules may go into limp mode or shut down
- Specific functions inoperative depending on module
- Diagnostic tools may show communication faults
Common causes
Ordered by how often each turns out to be the cause.
- Fuel pump module unpowered (often a fuse or relay)Common
- CAN wiring to FPCM brokenPossible
- Gateway module routing CAN messages incorrectlyLess likely
Parts involved
- Fuel Pump Control Module
- CAN Bus Wiring
U0109 is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.