AutoFixDB - Free OBD-II diagnostic trouble code lookup. Find causes, symptoms, diagnostic steps and repair solutions.

Overview

U0109 indicates a communication failure via the CAN bus between the Powertrain/Engine Control Module (PCM/ECM) and the Fuel Pump Control Module (FPCM), often causing no-start or drivability issues.

Common Symptoms

Check Engine Light illumination
Engine cranks but will not start
Intermittent stalling or rough running
Loss of fuel pump operation
Reduced power or hesitation

Most Common Causes

Open, shorted, or corroded CAN bus wiring or connectors high

Communication circuits (CAN high/low) disruption is the most frequently reported root cause.

Faulty Fuel Pump Control Module (FPCM) medium

Module failure prevents successful CAN communication with PCM/ECM.

Blown fuse or poor power/ground to FPCM medium

Loss of power or ground can mimic communication loss.

Faulty Powertrain/Engine Control Module low

Rare cause but possible when all wiring and module tests pass.

Diagnostic Steps

Connect a professional OBD‑II scanner and verify U0109 and any related communication codes.

Expected: U0109 present; other communication or powertrain codes may also appear.

Interpretation: Confirming code presence and additional codes helps isolate whether issue is isolated to FPCM communication.
Inspect fuses, relays, and power/ground for the fuel pump control module.

Expected: Fuses intact; proper constant power and good ground connections.

Interpretation: Blown fuse or poor ground indicates power supply issues rather than CAN communication failure.
Visually inspect wiring and connectors on CAN high/low and module leads for damage, corrosion, or loose pins.

Expected: No visible damage; connectors clean and seated.

Interpretation: Damage or corrosion suggests wiring repair before further module testing.
With battery disconnected, measure continuity/resistance on CAN bus circuits between PCM/ECM and FPCM.

Expected: Continuity present; resistance near specification (approx 60 ohms for CAN bus).

Interpretation: Open or high resistance indicates broken wire or poor connection.
Attempt direct communication with the FPCM using a scan tool.

Expected: FPCM responds to queries.

Interpretation: No response suggests wiring harness issue or module fault.

Repair Solutions

Repair or replace damaged wiring/connectors in the CAN bus and module circuits medium

Estimated Cost: $50 - $250

Often resolves the communication loss; costs vary with labor and vehicle complexity.

Replace the Fuel Pump Control Module (FPCM) hard

Estimated Cost: $600 - $1200

Include programming and calibration if required by the vehicle.

Replace blown fuses or repair poor grounds easy

Estimated Cost: $5 - $50

Basic electrical service; often a first step before advanced troubleshooting.

Replace PCM/ECM only after exhaustive wiring and module tests hard

Estimated Cost: $800 - $1500

Rare; only when confirmed defective after eliminating other causes.

Common Misdiagnoses

Avoid these common diagnostic mistakes:

Assuming the fuel pump itself is failed when the code indicates a communication issue rather than mechanical pump failure.
Replacing PCM/ECM without thorough CAN bus and power/ground testing.

Frequently Asked Questions

What is the definition of the U0109 engine code?

When your OBD-II scanner reads U0109, it means: Lost Communication with Fuel Pump Control Module. This code is related to the vehicle's Engine Mechanical.

Can U0109 cause engine damage?

With a severity level of high, the vehicle may crank but not start, stall, or suffer from fuel delivery interruption due to loss of communication with the fuel pump control module.

What happens when the U0109 code is active?

The most typical signs are: Check Engine Light illumination, Engine cranks but will not start, Intermittent stalling or rough running.

What causes the U0109 code?

This code is frequently triggered by: Open, shorted, or corroded CAN bus wiring or connectors, Faulty Fuel Pump Control Module (FPCM), Blown fuse or poor power/ground to FPCM.

Estimated repair costs for different causes of U0109

It depends on what needs to be fixed. Replace blown fuses or repair poor grounds repairs are cheaper (~$50), while Replace PCM/ECM only after exhaustive wiring and module tests repairs are on the higher end (~$1500).

Does U0109 affect Ford, Toyota, or Honda?

Yes, U0109 is a generic code that applies to all OBD-II compliant vehicles, including Ford, Toyota, Honda, Chevrolet, Nissan, Dodge, BMW, and more.

U0109: Lost Communication with Fuel Pump Control Module