U0109 — Data Bus: Fuel Pump (FP) Control Module – No Communication #

Please note: The code description and wording may vary slightly depending on the vehicle manufacturer (OEM). Always refer to your OEM’s service information for exact terminology.

Known Description Variations:

• Fuel Pump Module Communication Lost (GM, Ford)
• No Communication with Fuel Pump Control Module (Toyota, Nissan)
• Lost Communication with Fuel Pump Module A (Chrysler, Dodge, Jeep, RAM)
• Fuel Pump Control Module No Data Received (Volkswagen, Audi)

Summary of DTC U0109 #

Diagnostic Trouble Code (DTC) U0109 signals that the vehicle’s main controller (commonly the Powertrain Control Module or PCM) has lost digital contact with the Fuel Pump Control Module (FPCM). This communication occurs via the data network, known as the Controller Area Network (CAN) bus. When this link is broken, the PCM can’t monitor or command the fuel pump properly. As a result, the vehicle might experience drivability issues or even fail to start. This is a communication fault, not an immediate failure of the fuel pump itself. Restoring proper network function is crucial for reliable vehicle operation.

Frequent Symptoms for Code U0109 #

When U0109 is present, symptoms can range from subtle to severe. The most common clues that something is amiss include:

• Check Engine Light (CEL) illuminated or Service Engine Soon warning
• Crank-no start condition (engine turns over but won’t start)
• Hard starting or extended cranking time
• Sudden engine stalling while driving
• Poor engine performance or hesitation
• Reduced fuel efficiency
• No noise from the fuel pump when the ignition is turned on

Most Probable Causes for U0109 #

U0109 is most often triggered by a disruption in the communication line between the PCM and the FPCM. The following are the most common root causes, listed in order of likelihood:

1. Open, shorted, or corroded CAN bus wiring or connectors
2. Faulty Fuel Pump Control Module (FPCM)
3. Loose or poor electrical connection at the FPCM or PCM
4. Blown fuse or relay powering the FPCM
5. Battery voltage issues (weak battery, poor ground)
6. Faulty Powertrain Control Module (PCM) (rare)
7. Aftermarket installations disrupting wiring

Step-by-Step Diagnostic for U0109 #

A methodical approach is essential for tracing the cause of U0109. Use the following technician-tested steps:

• Verify the code: Confirm U0109 is current and not stored as a pending or historical code. Clear codes and check if it returns.
• Inspect fuses and relays: Check all fuses and relays related to the fuel pump system and FPCM. Replace any that are blown or suspect.
• Visual check of wiring and connectors: Examine CAN bus wiring, connectors at the FPCM, and related grounds for corrosion, damage, or loose pins.
• Check battery voltage: A weak battery or poor ground can cause communication loss. Ensure the battery is fully charged and all grounds are secure.
• Use scan tool to check network: Attempt communication directly with the FPCM using a diagnostic scanner. If the module is not detected, suspect wiring or module failure.
• Test CAN bus resistance: With the battery disconnected, measure resistance across CAN high and low wires at the FPCM connector. Compare to OEM specs (usually around 60 ohms).
• Check for aftermarket interference: Look for recent modifications (audio, alarms, remote start) that may have disrupted factory wiring.
• Substitute known-good module (if possible): As a last resort, replace the FPCM with a known-good unit to confirm module failure.

Possible Repairs for U0109 #

Once you’ve pinpointed the cause, the following repairs are commonly required to resolve U0109:

• Repair or replace damaged CAN bus wiring or connectors
• Replace the Fuel Pump Control Module (FPCM) if testing confirms failure
• Clean and secure all related electrical connections
• Replace blown fuses or faulty relays
• Correct battery or ground issues
• Restore wiring after removal of aftermarket equipment
• Replace or reprogram PCM (very rare, only after all other possibilities are exhausted)

Can You Drive With Code U0109? #

Short answer: It’s risky and not recommended. In some cases, the car may start and run intermittently, but loss of fuel pump control can cause sudden stalling or a no-start condition at any time. This poses a safety risk, especially if stalling occurs in traffic or at high speed. Always address U0109 promptly, and avoid driving until the cause is corrected.

Vehicles Most Commonly Affected by U0109 #

While U0109 can occur on virtually any modern vehicle equipped with a separate Fuel Pump Control Module, certain models are more frequently affected due to design and wiring layout. These often include:

• GM vehicles (Chevrolet, GMC, Cadillac, Buick, especially 2007–2016 trucks/SUVs)
• Ford and Lincoln (particularly F-Series trucks and SUVs, 2005–2018)
• Chrysler, Dodge, Jeep, RAM with separate FPCMs (2008+)
• Toyota and Lexus hybrids and late-model vehicles with smart fuel control
• Volkswagen and Audi models with networked fuel pump modules
• Nissan and Infiniti late-model cars and SUVs

Common Mistakes & Best Practices for U0109 #

It’s easy to misdiagnose U0109 if common pitfalls aren’t avoided. Keep these points in mind:

• Don’t replace the fuel pump itself unless it’s confirmed faulty—U0109 is a network code, not a pump failure code.
• Avoid overlooking basic checks like blown fuses or loose connectors.
• Don’t rush to replace control modules without thorough wiring and power/ground testing.
• Always clear codes and retest after any repair or wiring fix to confirm resolution.
• Document any aftermarket wiring or modifications found during diagnosis.

U0109 Quick FAQ #

Still have questions? Here are quick answers to common concerns:

• Q: Does U0109 mean my fuel pump is dead?
  A: Not necessarily. U0109 means the network can’t talk to the fuel pump control module, not that the pump itself has failed. The cause is often wiring or communication related.
• Q: Can a weak battery cause U0109?
  A: Yes, low system voltage or poor battery connections can interrupt module communication and trigger U0109. Always check battery state and grounds first.