U0109 on 2007-2014 GMC Yukon XL: Lost Communication With Fuel Pump Control Module Fixes

What's Unique About the 2007-2014 Gmc YUKON XL

On the GMT900 platform, which includes the 2007-2014 Yukon XL, the FPCM is notoriously prone to failure. This is primarily because GM mounted the module on a frame crossmember, usually above the spare tire, exposing it directly to road salt, water, and vibration. This design flaw leads to severe corrosion of the module's aluminum housing and electrical connector, making it a top failure point. Before assuming the expensive in-tank fuel pump has failed, investigating the FPCM on these trucks is a critical, money-saving first step.

Diagnostic Flowchart

Tap your situation to follow the diagnostic path that matches what you're seeing on this vehicle.

Symptoms You May Notice

• Engine cranks but will not start.
• Sudden loss of engine power while driving.
• Intermittent stalling.
• Check Engine Light is on.
• No audible 'hum' or 'whine' from the fuel pump when the key is turned to the 'ON' position.
• Reduced engine performance and rough running.

Most Likely Causes

1. Failed Fuel Pump Control Module (FPCM) 🔴 High Probability → Shop Fuel Pump The module is mounted under the vehicle above the spare tire, making it extremely vulnerable to corrosion from moisture and road salt, which damages its internal electronics and connector pins. The aluminum case is known to corrode and swell, allowing water intrusion.
   How to confirm: After verifying power and ground are present at the module's connector, use a scan tool to attempt direct communication. If the module has power but does not communicate, it has failed. Visually inspect for a swollen or corroded case.
   Typical fix: Replace the Fuel Pump Control Module. The new module must be programmed to the vehicle's VIN. Some owners relocate the new module to a drier location, such as inside the rear quarter panel.
   Est. part cost: $150-$270
2. Corroded Underhood Fuse Box or Blown Fuse 🟡 Medium Probability → Shop Fuse Box The underhood fuse box on these trucks is known to allow moisture entry, causing the terminals for the FPCM fuse (typically #21, a 20A fuse) to corrode and lose connection. This can create an intermittent open circuit that mimics a failed module.
   How to confirm: Visually inspect fuse #21 (and related fuses #20 and #56) and its terminals in the fuse box for green or white corrosion. Test for 12V power on both sides of the fuse. Wiggling the fuse while the engine is running may cause it to stall, confirming a bad connection.
   Typical fix: Clean the fuse terminals with a terminal cleaning tool and apply dielectric grease. If corrosion is severe, the entire fuse box may need to be replaced. Replace the fuse if blown.
   Est. part cost: $1-$5 for a fuse, $200-$400 for a fuse box.
3. Wiring Harness or Connector Damage 🟡 Medium Probability The wiring harness leading to the FPCM is routed along the frame and is susceptible to chafing, breaks, and corrosion, especially at the connector that plugs into the module. The pins in the connector itself are a common point of failure due to water damage.
   How to confirm: Visually inspect the entire length of the harness to the FPCM. Unplug the connector and check for corroded, bent, or broken pins. Test for continuity, power (Pink/Black wire), and ground (Black wire) at the connector with a multimeter.
   Typical fix: Repair the broken or corroded section of wire. Replace the connector pigtail if it is damaged. Common pigtail part numbers include ACDelco PT2712.
   Est. part cost: $20-$50 for a connector pigtail.

Rare But Worth Checking

• Faulty Engine Control Module (ECM): → Shop Engine Control Module (ECM) This is very rare. The ECM should only be considered after all other possibilities, including the FPCM, wiring, and fuses, have been definitively ruled out. Usually, other codes would be present if the ECM were failing.

Diagnosis Steps

1. Scan for all diagnostic trouble codes. Note any other 'U' codes, as they can point to a wider network problem. The presence of P069E alongside U0109 is a strong indicator the issue is localized to the FPCM circuit.
2. Open the underhood fuse box. Locate fuse #21 (FPCM, 20A) and inspect it and its terminals for corrosion or damage. Also check fuses #20 and #56.
3. Using a multimeter, confirm that you have 12V power at the FPCM fuse. A test light is even better to confirm the circuit can carry a load.
4. Safely raise the vehicle and lower the spare tire to gain access to the Fuel Pump Control Module (FPCM) on the frame crossmember.
5. Visually inspect the FPCM and its electrical connector for signs of corrosion, swelling, or physical damage. A swollen aluminum case is a tell-tale sign of internal failure.
6. Disconnect the FPCM connector. Check for 12V power (often a Pink/Black wire) and a solid ground connection (Black wire) on the appropriate pins using a multimeter and a wiring diagram.
7. Check the CAN bus wires (often a twisted pair) at the connector for proper resistance (typically around 60 ohms with the battery disconnected and FPCM unplugged).
8. If power, ground, and CAN bus wiring are all confirmed to be good, the Fuel Pump Control Module itself is faulty and must be replaced.
9. If a new FPCM is installed and programmed but the code returns, re-inspect the underhood fuse box terminals for a poor connection, as this is a common cause for comeback repairs.
🎬 See why this U0109 code can sometimes return after a repair.

Parts You'll Likely Need

• Fuel Pump Control Module (OEM #20850907) — This module is the most common point of failure for the U0109 code due to its poor mounting location leading to corrosion. Note: GM has superseded this part number multiple times; common replacements are 20759945, 25966043, and 20850907. The latest ACDelco part is often D1977F. 🎬 Check out this pre-programmed module that skips the dealer software step.
  Trusted brands: ACDelco, GM Genuine Parts, Dorman
  OEM price range: $150-$270
  Aftermarket price range: $100-$180

Related Codes That Often Appear With This One

• U0073 — Control Module Communication Bus 'A' Off. This is a general network code indicating a problem on the main CAN bus, often seen with TSB #08-07-30-021H.
• U0100 — Lost Communication With ECM/PCM. Often appears when network issues are present.
• U0101 — Lost Communication with TCM (Transmission Control Module). Indicates a wider network communication failure.
• P069E — Fuel Pump Control Module Requested MIL Illumination. This code is specifically set by the FPCM to tell the ECM there is a fault, often preceding a total communication loss (U0109). Seeing this code strongly points to the FPCM itself or its direct wiring/power supply.

Technical Service Bulletins (TSBs) & Recalls

• Bulletin #08-07-30-021H: Mentions that communication DTCs including U0109 can be set in conjunction with various electrical issues like door lock cycling and other warning lamps, pointing to a potential network-wide issue.
• NHTSA #14V614 / GM Campaign #14515: A safety recall was issued for a defective FPCM on many 2008-2014 models, including the Yukon XL, that could cause the engine to stall. This directly addresses the root cause of the U0109 code.

Platform-Specific Known Issues

• The placement of the FPCM above the spare tire is a known design flaw on 2007-2014 GM trucks and SUVs, leading to a high failure rate from corrosion.
• The underhood fuse box is susceptible to water intrusion, causing corrosion on multiple fuse terminals, including the one for the FPCM (Fuse #21), which can mimic a failed module.
• TSB #08-07-30-021H notes that U0109 can be set along with a host of other communication codes due to intermittent network issues, sometimes caused by connector problems elsewhere in the vehicle.
• GM issued a recall for some models (NHTSA #14V614, GM Campaign #14515) for a defective FPCM that could cause stalling, which is directly related to the U0109 fault.

Mechanic-Grade Diagnostic Values

• CAN Bus Network Resistance — expected: Approximately 60 Ohms. Failure: A reading of 120 Ohms indicates an open in one of the CAN wires or a missing termination resistor. A reading near 0 Ohms indicates a short between the CAN high and low wires.
• FPCM Connector Pin 32 (Red/White wire) Voltage — expected: Battery Voltage (12V+). Failure: No voltage indicates a loss of main power, likely from a blown Fuse #21 or a break in the power wire.
• FPCM Connector Pin 15 (Pink wire) Voltage — expected: Ignition 1 Voltage (12V+ with key in ON position). Failure: No voltage indicates a loss of the ignition signal to the module.
• FPCM Connector Pin 13 (Dark Green/White wire) Voltage — expected: 12V present for 2-6 seconds with key ON, or constant 12V when cranking.. Failure: No voltage indicates a break in the signal wire from the ECM or a faulty ECM.
• FPCM Connector Pin 1 (Black wire) to Chassis Ground Resistance — expected: Near 0 Ohms. Failure: High resistance indicates a poor ground connection, which is critical for module operation.

Scan Tool Commands That Help

• GDS2 / Tech2 / High-End Bidirectional Scanner: Fuel Pump On/Off Command — Use this command to manually activate the fuel pump. If the pump runs with this command but not during a normal start attempt, it suggests the FPCM is capable of working but is not receiving the proper command from the ECM, or there's an intermittent wiring issue.
• GDS2 / Tech2 / High-End Bidirectional Scanner: FPCM Data Display — Monitor the live data from the FPCM to check parameters like 'Ignition 1 Signal' or 'Module Voltage'. This can confirm if the module is receiving the necessary power and ignition signals without needing to physically probe the wires.
• ACDelco TDS with SPS (Service Programming System): Module Programming/Setup — This is required after installing a new, unprogrammed FPCM. The software downloads the correct calibration for the vehicle's VIN and programs it to the new module, allowing it to communicate with the other vehicle systems.

Wiring & Ground Locations

• FPCM Connector (X411) — On the Fuel Pump Control Module, mounted to the frame crossmember above the spare tire.. This is the central connection point for all power, ground, and communication lines for the module. Corrosion or damage here is a primary cause of U0109.
• FPCM Ground (Pin 1) — The Black wire at Pin 1 of the FPCM connector. It is grounded to the vehicle's frame near the module.. A poor ground connection will prevent the module from powering up and communicating, directly causing a U0109 code even if power is present.
• ECM Connector (Black) — At the Engine Control Module (ECM) in the engine bay.. Pin 50, a Dark Green/White wire, is the source of the fuel pump enable signal. If this signal is missing at the FPCM (Pin 13), checking for 12V at ECM Pin 50 can determine if the ECM is faulty or if the wire is broken between the two modules.
• Harness Chafe Point (4WD Models) — The wiring harness may rub against the transfer case on 4-wheel-drive models.. A technician noted that the Dark Green/White signal wire can chafe and break in this location, causing an intermittent or total loss of the 'turn-on' signal to the FPCM. This is an easily missed failure point if the inspection is only focused at the rear of the vehicle.

Real Owner Repair Stories

• YouTube channel 'Phillip Bailey' (2011 GMC Sierra (GMT900 Platform)) — Crank no start, comeback repair. The truck would not start for the customer the day after the FPCM was replaced.
  ❌ Tried (didn't work) Initially replaced the Fuel Pump Control Module (FPCM), which seemed to fix the problem temporarily.
  ✅ What actually fixed it The root cause was a poor, corroded connection at Fuse #21 in the underhood fuse box. Even though the circuit tested good with a load test (headlight), the corrosion created an intermittent failure. The mechanic confirmed this by wiggling the fuse while the truck was running, which caused it to stall and reset the U0109 code. The final repair was to replace the entire underhood fuse box due to widespread corrosion on multiple terminals.

OEM Part Supersession History

• 20964304 → 20850907, D1977F (ACDelco) — Part revision and consolidation.
  Heads up: Some sources list different part numbers for 2007-2009 (e.g., 20964304) vs. 2010-2014 (e.g., 20964305), suggesting internal software or hardware differences. Always verify the correct part number by VIN before ordering.

Model Year Variations Within This Range

• 2007-2009 vs 2010-2014: The original equipment FPCM part number may differ between the early and later years of this generation. For example, 2007-2009 models may use PN 20964304, while 2010-2014 models may use PN 20964305. While modern replacement parts often cover the entire year range, this indicates a change in the original production parts that may be relevant when sourcing used components.