U0109 on 2007-2014 Chevrolet Tahoe: Lost Communication With Fuel Pump Control Module Fixes

What's Unique About the 2007-2014 Chevrolet TAHOE

On the GMT900 platform, which includes the 2007-2014 Tahoe, the FPCM is notoriously mounted on the driver's side frame rail, often above the spare tire. This exposed location makes the module and its electrical connector highly susceptible to corrosion from road salt, water, and debris. The connector pins face downward, which can trap moisture and accelerate corrosion. This design choice is the primary reason U0109 is a relatively common and well-documented issue for these trucks. Furthermore, frame grounds like G300 (under the driver door) and others are prone to corrosion from undercoating or road grime, which can cause intermittent power issues to the module.

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 engine stalling, sometimes intermittently.
• Reduced engine power or hesitation.
• Check Engine Light (Malfunction Indicator Lamp) is illuminated.
• Transmission may not shift correctly (often seen with other communication codes).
• No audible hum from the fuel pump when the key is turned to the 'ON' position.

Most Likely Causes

1. Failed Fuel Pump Control Module (FPCM) 🔴 High Probability → Shop Fuel Pump The module is mounted on the frame rail, where it is exposed to moisture and road salt, leading to internal failure from corrosion or vibration. Water intrusion is common, especially on vehicles used to launch boats.
   How to confirm: After verifying power, ground, and communication lines to the module are intact, the module itself is the likely culprit. A scan tool may show it as offline. Wiggling the connector may cause intermittent communication loss if the terminals inside the module are failing.
   Typical fix: Replace the Fuel Pump Control Module. Many aftermarket options from brands like Dorman come pre-programmed, avoiding a trip to the dealer for programming.
   Est. part cost: $80-$200
2. Corroded FPCM Connector or Wiring 🟡 Medium Probability The same exposed mounting location that damages the module also causes corrosion on the connector pins and wiring harness. The downward-facing pins can trap moisture.
   How to confirm: Visually inspect the FPCM connector for green or white corrosion, swollen wires, or backed-out pins. A poor connection on the pink ignition voltage wire is a common finding. Wiggle the harness while monitoring communication status with a scan tool.
   Typical fix: Clean the connector if corrosion is minor. If damage is severe, replace the connector with a new pigtail (e.g., ACDelco PT2799).
   Est. part cost: $20-$50
3. Blown or Corroded Fuse for the FPCM ⚪ Low Probability The underhood fuse block on GMT900 trucks is known to be susceptible to internal corrosion, which can cause poor contact and intermittent power loss to the FPCM circuit.
   How to confirm: Check fuse #21 (FSCM) and fuse #56 (ECM IGN) in the underhood fuse block for power with the key on. Remove the fuses and inspect the metal legs for corrosion. A real-world repair showed a recurring U0109 was solved by cleaning corrosion from the fuse #21 terminals in the fuse block itself. 🎬 See this video for locating the fuel control module fuse.
   Typical fix: Replace the blown fuse. If the fuse block itself is corroded, it may need to be cleaned or replaced.
   Est. part cost: $1-$10 for a fuse, $150-$300 for a fuse block.
4. Poor Ground Connection ⚪ Low Probability Frame grounds are susceptible to rust and corrosion. A poor ground can cause intermittent module operation. The primary ground for this area is G300, located on a body mount under the driver's door.
   How to confirm: Locate the ground for the FPCM on the frame rail (often G300). Remove the bolt, and clean the contact surfaces of the eyelet and frame to bare metal. A forum user noted that low system voltage from a bad ground can cause multiple seemingly unrelated codes along with fuel system issues.
   Typical fix: Clean and secure the ground connection.
   Est. part cost: $0

Rare But Worth Checking

• CAN Bus Network Fault: If multiple 'U' codes (e.g., U0073, U0100, U0101, U0121) are present along with U0109, it points to a wider network problem, not just the FPCM circuit. TSB #08-07-30-021H describes this scenario, often caused by chafed wiring in the transmission harness connector (X150/X109) or corrosion in other module connectors. The bulletin explicitly states not to replace modules until the wiring has been thoroughly inspected.

Diagnosis Steps

1. Scan for all DTCs in all available modules. Note if U0109 is alone or present with other communication codes, which would suggest a wider network issue per TSB #08-07-30-021H.
2. Locate the FPCM on the driver's side frame rail, near the rear door or above the spare tire.
3. Visually inspect the FPCM and its connector for physical damage, corrosion, or water intrusion. Pay close attention to the pins for any green or white powder.
4. Check the fuses related to the FPCM/FSCM (typically fuse #21, a 20A fuse) and the ECM ignition feed (fuse #56) in the underhood fuse block. Inspect the fuse terminals for corrosion, not just if the fuse is blown.
5. Using a multimeter, verify battery voltage on the appropriate power wire (often a pink wire for ignition voltage) and a good ground at the FPCM connector.
6. Check the CAN bus wires (typically a twisted pair) at the connector for proper voltage (around 2.5V, fluctuating slightly) and resistance. With the battery disconnected, measure resistance between the two CAN wires (often pins 6 and 14 on the OBD-II port); it should be 60 ohms.
7. If power, ground, and communication lines test good, the FPCM is faulty and should be replaced.

Parts You'll Likely Need

• Fuel Pump Control Module (FPCM) (OEM #13506835) — This module is the most common point of failure due to its exposed mounting location leading to corrosion and internal faults.
  Trusted brands: ACDelco (Professional or GM Genuine), Dorman OE Solutions (e.g., 601-132)
  OEM price range: $150-$250
  Aftermarket price range: $80-$150
• Fuel Pump Control Module Connector Pigtail (OEM #ACDelco PT2799) — If the connector is heavily corroded, it must be replaced to ensure a reliable connection to the new module. 🎬 Watch: How to repair and replace a corroded FPCM connector.
  Trusted brands: ACDelco, Dorman
  OEM price range: $30-$60
  Aftermarket price range: $20-$40

Related Codes That Often Appear With This One

• U0100 — Lost Communication with ECM/PCM. This can appear if there's a broader network issue.
• U0101 — Lost Communication with TCM. Often appears with other communication codes as described in TSB #08-07-30-021H, pointing to a shared network wiring problem.
• P0562 — System Low Voltage. This code was reported on a forum along with other fuel system codes, suggesting a weak battery or poor ground connection could be the root cause.

Technical Service Bulletins (TSBs) & Recalls

• 08-07-30-021H: Addresses loss of high-speed GMLAN communications, which can set various U-codes including U0109, and may cause symptoms like no-start, gauge fluctuation, and shifting problems. It covers 2007-2014 Tahoe, Suburban, Silverado, Sierra, Escalade, and others.
• PIT4853C: While focused on Hybrid models, this bulletin also references TSB 08-07-30-021 and points to checking ground G300 for poor connection due to undercoating, a relevant check for non-hybrid models as well.

Platform-Specific Known Issues

• TSB #08-07-30-021H addresses widespread GMLAN communication failures that can cause U0109 along with many other codes. The bulletin points to potential wiring issues, particularly in the transmission harness connector, as a possible cause for these network-wide outages.
• A recurring U0109 on a 2011 GM truck was traced back to a corroded terminal for fuse #21 in the underhood fuse block, even after the FPCM was replaced. The technician had to remove and clean the fuse block itself to solve the problem.
• The FPCM ground is often tied to ground point G300, located under the vehicle at the driver's door on a body mount. This area is prone to collecting dirt and undercoating, which can compromise the connection.

Mechanic-Grade Diagnostic Values

• GMLAN Bus Resistance — expected: 60 Ohms (± 5 Ohms). Failure: A reading of 120 Ohms indicates an open in the bus or a missing terminating resistor. A reading near 0 Ohms indicates the CAN High and Low wires are shorted together.
• FPCM Ignition 1 Voltage — expected: 11.5 - 12.5 Volts (Key On). Failure: Low or no voltage on the Pink wire at the FPCM connector indicates a problem with the power supply from the fuse block, not the module itself.
• CAN Bus Voltage (Key On) — expected: CAN High and CAN Low should both be approximately 2.5V to ground, with slight fluctuations. CAN High biases slightly above 2.5V and CAN Low biases slightly below during communication.. Failure: A wire stuck high (at 5V or 12V) or low (at 0V) indicates a short to power or ground.

Scan Tool Commands That Help

• GDS2 (Global Diagnostic System 2): Fuel Pump Driver Control Module Configuration — This function is required after replacing the Fuel Pump Control Module to ensure it is properly configured for the vehicle's specific options. A GDS2 software update was released to add this function which was initially missing for some models.
• Bi-directional Scan Tool (e.g., Tech2, GDS2): Fuel Pump On/Off Command — To verify if the FPCM is capable of receiving commands and activating the fuel pump. If the pump runs with the scan tool command but not during a normal key cycle, it points to a communication or command signal issue rather than a failed pump or module.

Wiring & Ground Locations

• FPCM Connector — On the Fuel Pump Control Module, located on the driver's side frame rail, often near the spare tire.. This is the primary point for testing power, ground, and communication signals. Key pins include: Pin 1 (Black) for Ground, Pin 16 (Pink) for Ignition 1 Voltage, Pin 32 (Red/White) for Battery Positive Voltage, and the twisted pair of Tan and Tan/Black wires for the GMLAN bus.
• G300 — Under the vehicle at the driver's door on a body mount.. This is a primary ground point for components in the rear of the vehicle, including the FPCM. Corrosion or looseness at this point due to undercoating or road grime can cause intermittent power and communication issues for the module.
• Underhood Fuse Block — Driver's side of the engine bay.. Houses Fuse #21 (FSCM 20A) and Fuse #56 (ECM IGN 15A). The internal terminals of the fuse block itself can corrode, creating a poor connection for the fuse and causing intermittent power loss to the FPCM, even if the fuse itself is good.
• G103 — On the front of the passenger side cylinder head.. While not the primary FPCM ground, poor engine and body grounds can create voltage potential differences that disrupt sensitive module communications. Ensuring all major grounds are clean and tight is a crucial step in diagnosing network codes.

Real Owner Repair Stories

• YouTube channel 'Phillip Bailey' (2011 GM Truck) — Crank no start, recurring U0109 code.
  ❌ Tried (didn't work) Replacing the Fuel Pump Control Module (FPCM). The truck ran but the problem returned the next day.
  ✅ What actually fixed it The terminals for fuse #21 (FSCM) in the underhood fuse block were corroded, causing an intermittent connection. The technician had to remove the fuse block, clean the corroded terminals within it, and apply dielectric grease before reinstalling to create a reliable connection.
• Tahoe Yukon Forum user 'K9ErnieSSV' (2014 Tahoe SSV) — Check Engine Light, Service Trailer Brake message, codes P069E and P2534.
  ❌ Tried (didn't work) Replacing both batteries., Cleaning grounds near the FPCM.
  ✅ What actually fixed it The issue was self-induced. The owner had removed a fuse tap from fuse slot #43 (Aux HVAC) that was leftover from police equipment. This seemingly unrelated fuse was also part of the Ignition 1 signal circuit for the FPCM. Reinstalling a fuse in this slot resolved the FPCM codes.
• YouTube channel 'Hands On Auto Training' (2008 Chevy Tahoe) — Intermittent no crank/no start, code for 'ignition one circuit voltage low' in FPCM.
  ❌ Tried (didn't work) Wiggling harnesses to find a chafed wire.
  ✅ What actually fixed it The female terminals inside the FPCM connector were spread or 'opened up', likely from improper probing during previous diagnosis. This caused a poor connection on the pink ignition power wire. The fix was to de-pin the connector and tighten the spread terminals to ensure a solid connection with the module's pins.

When the Usual Fixes Don't Work

• While the most common fix is replacing the FPCM, a significant number of real-world repair stories show that the problem was actually upstream from the module. In one case, a 2011 GM truck with a recurring U0109 had its FPCM replaced, but the issue persisted. The root cause was found to be corrosion on the fuse terminals inside the underhood fuse block, which required cleaning the block itself to achieve a permanent fix. This highlights the importance of verifying a stable power supply at the FPCM connector before condemning the module.

OEM Part Supersession History

• 25785013, 20759945, 25967325 → 13506835 (among others, part numbers frequently update) — Part numbers are often superseded due to minor manufacturing changes, updated internal software, or different suppliers.
  Heads up: While many modules are physically identical, they require programming to the vehicle's VIN. Some aftermarket modules come pre-programmed, but a used module from another vehicle will likely not work without being reprogrammed by a dealer or specialist.

Model Year Variations Within This Range

• 2007-2014: There are no significant documented changes to the location or primary failure mode of the FPCM within this generation. However, part numbers for the module itself may have been updated several times. Always verify the correct part number for a specific year and VIN.