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

What's Unique About the 2007-2014 Chevrolet SUBURBAN

On the GMT900 platform, which includes the 2007-2014 Suburban, the Fuel Pump Control Module (FPCM) is notoriously mounted on the frame rail, often on a cross-member directly above the spare tire. This location exposes it to significant moisture, road salt, and debris kicked up by the tires. The module's design and orientation can trap this corrosive material, leading to failure of the module's internal electronics and severe corrosion of its electrical connector and wiring. This design choice is a primary contributor to the high failure rate of this specific part on these trucks, making U0109 a relatively common code.

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.
• Transmission may not shift properly (as part of a larger network issue). [Bulletin #08-07-30-021H]
• Various other warning lamps may be illuminated on the instrument panel. [Bulletin #08-07-30-021H]

Most Likely Causes

1. Failed Fuel Pump Control Module (FPCM) 🔴 High Probability → Shop Fuel Pump The module is mounted on the frame rail above the spare tire, making it highly susceptible to corrosion from water and road salt, which damages internal electronics and the connector pins.
   How to confirm: After verifying power, ground, and communication lines to the module are intact, the module itself is the most likely culprit. A definitive test is to swap with a known good module. Visually, the old module may have a swollen or cracked case from internal corrosion.
   Typical fix: Replace the Fuel Pump Control Module. OEM replacements may require programming to the vehicle's VIN, but several aftermarket options (like Dorman) are pre-programmed and plug-and-play. It is highly recommended to apply dielectric grease to the connector 🎬 Watch: Important replacement and programming tips for GMT900 trucks. of the new module to prevent future corrosion.
   Est. part cost: $70-$270
2. Corroded or Damaged Wiring/Connector 🟡 Medium Probability The same environmental factors that damage the module also affect its electrical connector and the nearby wiring harness. Pins can corrode and turn green/white, and wires can fray or break.
   How to confirm: Visually inspect the FPCM connector for green or white corrosion, bent pins, or damaged wires. Use a multimeter to check for proper voltage (Pin 32), ground (Pin 1), and CAN bus signals (Pins 6 & 7 or 22 & 23 depending on year/diagram) at the connector.
   Typical fix: Clean the connector terminals carefully with an electrical contact cleaner and a small brush. If corrosion is severe, the connector pigtail must be replaced. Damaged sections of the wiring harness must be repaired or spliced.
   Est. part cost: $20-$60 for a new pigtail connector.
3. Blown Fuse for FPCM ⚪ Low Probability Corrosion in the under-hood fuse box is also a known issue on GMT900 trucks, which can cause poor contact or a blown fuse for the FPCM. A short circuit in the FPCM or its wiring can also cause the fuse to blow repeatedly.
   How to confirm: Locate the fuse for the FPCM (labeled 'FSCM' or similar) in the under-hood fuse box and check for continuity. For the 2007-2014 Suburban, check the 20A fuse in position #21. Check for corrosion on the fuse legs and in the fuse slot itself.
   Typical fix: Replace the blown fuse. If the fuse slot is corroded, it must be cleaned. If the fuse blows again immediately, it indicates a short circuit in the wiring or a failed FPCM that needs to be diagnosed further.
   Est. part cost: $1-$5

Rare But Worth Checking

• Faulty Powertrain Control Module (PCM): → Shop Engine Control Module (ECM) This is very uncommon. Before suspecting the PCM, all other possibilities, including wiring, fuses, and the FPCM itself, should be exhaustively ruled out. A faulty PCM will typically set other communication codes as well.
• CAN Bus Network Failure: A break or short in the main communication network wiring can cause this code, but it will almost always be accompanied by a host of other U-codes from various modules (e.g., U0100, U0101, U0121). The provided TSB #08-07-30-021H mentions this scenario. A user on a Reddit forum mentioned checking a communication line connector under the driver's side dash.

Diagnosis Steps

1. Check for other DTCs. If multiple 'U' codes are present (like U0100, U0101), suspect a wider network problem rather than just the FPCM.
2. Locate the FPCM. On the 2007-2014 Suburban, it is mounted to the frame cross-member above the spare tire. You will likely need to lower the spare tire for access.
🎬 Watch: How to locate and replace the module on your Suburban.
3. Visually inspect the FPCM and its connector for any signs of physical damage, water intrusion, or corrosion (green/white powder). The module case may be cracked or swollen.
4. Check the FPCM fuse. In the under-hood fuse box, inspect the 20A fuse in slot #21 (sometimes labeled FSCM-B+). Check the fuse and the slot for corrosion.
5. With the key on, use a multimeter to verify battery voltage and a solid ground at the FPCM connector. A wiring diagram is essential. 🎬 See this walkthrough for diagnosing a crank-no-start with no communication. Check for 12V+ at the Red/White wire (Pin 32) and good ground at the Black wire (Pin 1).
6. Check the communication lines. Using a multimeter, check the CAN bus communication wires (often a twisted pair, e.g., Tan and Tan/Black) for continuity and resistance between the FPCM connector and the PCM.
7. If all wiring, power, and grounds are confirmed to be good, the Fuel Pump Control Module is the most likely failed component.

Parts You'll Likely Need

• Fuel Pump Control Module (OEM #20850907, 20759945) — This module is the most common failure point for code U0109 on this vehicle due to its vulnerable mounting location leading to corrosion and internal failure.
  Trusted brands: ACDelco (GM Genuine), Dorman (e.g., 590-205, often pre-programmed)
  OEM price range: $200-$270
  Aftermarket price range: $70-$150
• FPCM Connector Pigtail (OEM #22790584) — If the connector is heavily corroded, it may be impossible to clean and will need to be replaced to cut out and replaced to ensure a good connection to the new module.
  Trusted brands: ACDelco, Dorman, Standard Motor Products
  OEM price range: $40-$70
  Aftermarket price range: $20-$50

Related Codes That Often Appear With This One

• U0100 — Lost Communication with ECM/PCM. This can appear if the entire CAN bus is compromised.
• U0101 — Lost Communication with TCM. Often set alongside other U-codes when a network-wide issue is present, as noted in TSB #08-07-30-021H.
• U0073 — Control Module Communication Bus 'A' Off. This is a general network code indicating a problem with the main CAN bus, which would prevent modules like the FPCM from communicating.
• P069E — Fuel System Control Module Requested MIL Illumination. This code is often set in conjunction with U0109 and indicates the FPCM has detected an internal fault and has asked the PCM to turn on the Check Engine Light.

Technical Service Bulletins (TSBs) & Recalls

• 08-07-30-021H: Notes that communication DTCs including U0109 can occur with various electrical symptoms like warning lamps and shifting issues.
• PIT5379A: Addresses crank/no-start with U0109, advising technicians to inspect the FPCM and its connector for corrosion.

Platform-Specific Known Issues

• The provided Technical Service Bulletin #08-07-30-021H lists U0109 as a potential communication DTC that can set along with symptoms like door lock cycling, various warning lamps, and the transmission not shifting, pointing to potential network-wide electrical issues on these vehicles.
• Another TSB, PIT5379A, addresses a crank/no-start or stall condition with code U0109, specifically pointing to checking for corrosion at the FPCM connector due to its location above the spare tire.

Mechanic-Grade Diagnostic Values

• CAN Bus Network Resistance — expected: ~60 Ω. Failure: A reading of ~120 Ω indicates a missing termination resistor or a break in one of the CAN lines. A reading near 0 Ω indicates a short between CAN_H and CAN_L.
• CAN Bus Voltage (Key On, Engine Off) — expected: CAN_H and CAN_L should both read ~2.5V in the idle (recessive) state. During communication, CAN_H will toggle to ~3.5V and CAN_L will toggle to ~1.5V (dominant state).. Failure: Voltages stuck high or low, or no voltage, indicates a short to power/ground or an open circuit.
• FPCM Power Supply Voltage — expected: Should be equal to battery voltage (~12.4V or higher) with the key on.. Failure: Low or no voltage indicates a problem with the power supply wire or, more commonly, high resistance at the under-hood fuse block (Fuse #21).
• FPCM Control Signal to Fuel Pump — expected: A 25 KHz Pulse Width Modulated (PWM) signal. The duty cycle will vary based on fuel demand from the ECM.. Failure: No signal or a flat-line voltage indicates a failed FPCM or a loss of communication/power to the FPCM.

Hidden / Shadow Codes Worth Checking

• P069E: Fuel Pump Control Module Requested MIL Illumination. This is set by the PCM when the FPCM detects an internal or circuit-related fault and sends a message over the CAN bus requesting the Check Engine Light be turned on. It's a strong indicator that the fault originates at the FPCM. (see via Standard OBD-II scanner.)
• P0606: Internal Control Module Processor Fault. When this code is present for the FPCM, it means the module's internal microprocessor has failed its self-test, confirming the module itself is bad. (see via A professional-grade scanner that can read codes from specific modules, not just the PCM.)
• B1001: Option Configuration Error. This code can appear if a replacement FPCM is installed but not correctly programmed or configured for the vehicle's specific options. (see via A professional-grade scanner like the GM GDS2.)

Scan Tool Commands That Help

• GM GDS2 / Tech2 or equivalent bidirectional scanner: Fuel Pump On/Off Command (or Fuel Pump Relay Command) — This is a critical bidirectional test. If you suspect the FPCM or wiring, you can use this command to directly energize the fuel pump. If the pump runs with this command, it confirms the wiring from the FPCM to the pump and the pump itself are likely good, pointing the diagnosis towards the FPCM or its inputs (power, ground, data).
• GM GDS2 / Tech2: Fuel Pump Driver Control Module Configuration / Reset — This function is required after installing a new OEM FPCM. It allows the new module to learn the vehicle's VIN and specific configuration. Skipping this step can result in a no-start condition or other fault codes even with a new part.

Wiring & Ground Locations

• Fuse #21 (Under-hood Fuse Block) — In the main fuse box in the engine compartment, typically a 20A fuse.. This fuse provides the main battery power to the FPCM. These fuse blocks are known to get corrosion on the internal terminals, causing intermittent high resistance and power loss to the FPCM, which directly causes a U0109 code.
• G305 — Under the vehicle, on the frame near the third body mount, to the rear of the driver's side B-pillar.. This is a major frame ground point for components in the middle and rear of the vehicle. A corroded or loose G305 can cause an intermittent or missing ground for the FPCM, preventing it from operating.
• G401 — On the left rear frame rail.. This is the primary ground point for the rear lighting and other components on the driver's side rear of the frame. It is a likely candidate for the FPCM's ground path and is exposed to the same elements as the FPCM itself.

Real Owner Repair Stories

• YouTube video by professional technician Phillip Bailey / 'Phillip Bailey' (2011 GMC Sierra (same GMT900 platform and FPCM system as Suburban)) — Crank no start, code U0109. Vehicle came back the day after the FPCM was replaced with the same issue.
  ❌ Tried (didn't work) Replacing the Fuel Pump Control Module (FPCM). The fix only lasted one day.
  ✅ What actually fixed it The root cause was severe corrosion on the terminals for Fuse #21 inside the under-hood fuse block. The fuse itself looked okay, but the connection was intermittent. The technician noted multiple other fuses also had corrosion, and the entire fuse block assembly had to be replaced to provide a reliable power source to the FPCM.

"I Checked Everything" — The Actual Cause

• A common misdiagnosis pattern for U0109 is to confirm power and ground at the FPCM connector, find them present, and condemn the module. However, the actual fault can be high resistance at the under-hood fuse block (Fuse #21). A simple voltage check might show 12V, but the corroded connection cannot supply the necessary amperage to run the module and pump, causing it to shut down and log a communication code. A technician in one documented case load-tested the circuit from the FPCM and it passed, but the intermittent nature of the corroded fuse terminal caused the problem to return until the entire fuse block was inspected and replaced.

OEM Part Supersession History

• 20850907 → 20759945 — Standard part revision and improvement by the manufacturer.
  Heads up: Using an OEM module (like 20850907 or 20759945) requires programming/configuration to the vehicle's VIN using a GM GDS2/Tech2 scan tool. Failure to program the module will likely result in a no-start condition and may set configuration error codes like B1001.
• Multiple (e.g., 25866052, 25967325) → 20850907 / 20759945 — Part consolidation and updates over the production run.
  Heads up: Always verify the correct part number for your specific VIN. While many aftermarket modules (e.g., Dorman) are sold as 'plug-and-play' (pre-programmed), OEM modules are not and must be configured electronically.

Model Year Variations Within This Range

• 2007-2014: While the physical location and failure mode of the FPCM are consistent across the generation, the specific OEM part number may have changed several times. Regardless of the year, replacement of an original GM module with a new GM module requires a 'Fuel Pump Driver Control Module Configuration' procedure using a dealer-level scan tool to program it to the vehicle.