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Home / Codes / U0109
DTC code page

U0109: Lost Communication With Fuel Pump Control Module

Quick answer: Another module stopped hearing the fuel pump control module on the vehicle network.

Drivers also search this fault as lost communication with fuel pump control module, fuel pump module offline, U0109 fuel pump communication fault.

Severity: high Family: network Related paths: 14
Meaning

What U0109 usually means

U0109 means the fuel pump control module stopped reporting normally over the network. On vehicles that use a separate fuel pump driver or control module, that matters because the module is the middleman between fuel-pressure demand and what the pump actually does. When it drops offline, the car may crank too long, stall, refuse to start, or suddenly stack fuel-pressure and low-voltage style faults that look mechanical until you notice the communication loss.

Fast triage

Start here before chasing parts

  • Scan first: save freeze-frame and pending codes before clearing anything.
  • Confirm the complaint: compare the stored code with current drivability symptoms.
  • Use context: trims, live data, and related codes usually narrow the fault faster than guesswork.
  • Work simplest to hardest: leaks, connectors, maintenance items, and known patterns before expensive components.
Initial checks

What to check first

  • Ask whether the vehicle also has long-crank, no-start, or reduced-fuel-pressure symptoms because U0109 matters much more when drivability changed with it.
  • Check battery and charging condition early since weak voltage can silence modules and destabilize fuel control together.
  • Inspect the fuel pump module area for corrosion or water exposure because many are mounted in locations that collect road spray.
Driving risk

Can you keep driving?

U0109 can quickly turn into a no-start or stall complaint because fuel delivery control depends on this module staying awake and reachable. Diagnose it promptly instead of continuing to clear the code.

High urgency: If symptoms are active, reduce driving and diagnose quickly before secondary damage builds.
Likely causes

Common causes behind this code

  • Fuel pump control module power or ground failure
  • Communication wiring fault between the module and the rest of the network
  • Water intrusion or corrosion at the module or connector near the frame or rear body
  • Low system voltage resetting the module under load or during cranking
  • Internal failure of the fuel pump control module itself

Cause phrases often tied to this code: fuel pump module power loss, CAN wiring issue, module corrosion, low voltage, failed fuel pump driver module.

Diagnostic order

Suggested workflow

  1. Scan all modules and confirm whether the fuel pump control module communicates directly.
  2. Verify the module power feeds, grounds, and wake-up circuits under load.
  3. Inspect the module connector, wiring, and mounting area for water intrusion, corrosion, or damaged pins.
  4. Check companion fuel-pressure and fuel-pump circuit codes to see whether the communication fault is part of a wider control problem.
  5. Only condemn the module after external voltage supply and communication integrity are proven.
Avoid guesswork

Common mistakes

  • Replacing the in-tank fuel pump because the engine has low pressure without checking whether the driver module is even online.
  • Ignoring low battery or charging instability that can make a healthy module vanish temporarily.
  • Treating U0109 like a pure network code and missing the fuel-delivery consequences.
Repair path

Practical fix guidance

  • Repair the proven module power, ground, connector, or network fault before replacing the control module.
  • If the module is corroded or water-damaged, fix the mounting or sealing issue so the replacement does not fail the same way.
  • After repair, verify normal starting, stable pressure control, and full module communication.
Vehicle context

Affected brands in this MVP

Brand hubs help broaden internal linking now and can evolve into make-specific diagnostic notes later.

Aliases and common searches

English phrases tied to U0109

Useful when the driver knows the wording but not the exact DTC yet.

  • lost communication with fuel pump control module
  • fuel pump module offline
  • U0109 fuel pump communication fault
Related search intent

Queries this page can answer naturally

  • U0109 code meaning
  • what does U0109 mean
  • lost communication with fuel pump control module
  • fuel pump module not communicating
FAQ

Quick questions about U0109

Can U0109 cause a crank-no-start?

Yes. If the fuel pump control module is offline, the pump may not be commanded correctly and the engine can crank without starting.

Is U0109 the same as a bad fuel pump?

No. The pump itself can be fine while the control module or its power and communication path fail.

Why is corrosion common with U0109?

Many fuel pump driver modules live under the body or near the rear of the vehicle where water and salt exposure are harsh.