U0109: How to Diagnose & Fix — Lost Communication With Fuel Pump Control Module "A"
2 vehicles · 2 makes · $250-$1,400 repair
How to diagnose and fix U0109: most-reported vehicles
Ranked by owner reports. Each card gives the symptoms, how to confirm the cause, the fix, parts and sources for that vehicle.
Buick Envision · 2021–2023
Second-generation Envisions have a repeating NHTSA pattern of the fuel pump control module failing, producing an engine that dies without warning while driving and a crank-no-start afterward, or that only fires on 7-8 of every 10 attempts. Owners report no warning lights and no stored codes in several cases. One especially dangerous report describes the vehicle stalling in a center freeway lane where the electronic shifter would not allow neutral with the engine off, stranding the car in traffic. Failures are documented from about 11,000 miles, and replacement modules have been back-ordered for extended periods.
Common Symptoms
- Engine dies while driving with no warning
- Cranks but will not start, intermittently
- No check engine light or stored trouble codes at the time of failure
- Vehicle stalls and cannot be shifted to neutral to be pushed
How to Fix
Check fuel pressure and fuel pump power/enable at the module before replacing the pump assembly. The repair is replacement of the fuel pump control module (typically mounted at the rear of the vehicle) followed by module programming. Check GM's open recall and field-action list against your VIN, and verify the vehicle's shift-to-neutral procedure with the engine off so you can move it if it strands you.
Sources for this issue (2)
Chevrolet Silverado · 2007–2013
GMT900 Silverados (and the late GMT800) mount the fuel pump control module / fuel-system control module on an exposed frame-rail bracket where it is constantly hit with road salt, water and debris. The module's connector and internals corrode, and the FPCM then fails to drive the in-tank pump — producing extended cranking, intermittent stalling, and ultimately a crank-but-no-start with no fuel pressure. Because the pump itself is often fine, owners frequently mis-diagnose and replace the in-tank pump first. A common, well-documented salt-belt failure with steady search demand.
Common Symptoms
- Crank but no start / engine won't fire
- Extended cranking before starting
- Intermittent stalling while driving
- No fuel-pump prime sound at key-on
- Loss of power / hesitation
- Fuel-system codes / pump not commanded on
How to Fix
Diagnose by checking for fuel-pump prime/pressure and FPCM communication and inspecting the frame-mounted module connector for corrosion. The fix is to replace the corroded fuel pump control module (a new programmed module is required; GMT900 OE 20759945 / later 13543038 family) and clean/repair the connector and grounds; relocating or sealing the connector helps prevent recurrence. Rule out blown fuse/relay and a genuinely failed in-tank pump first.
Sources for this issue (1)
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U0109 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does U0109 mean?
U0109 stands for "Lost Communication With Fuel Pump Control Module "A"." Sets when a module loses data-bus communication with the Fuel Pump Control Module 'A', which regulates electric fuel pump operation/pressure. Loss of these messages can interrupt fuel delivery.
What are the most common causes of U0109?
The most common causes of U0109 are: Open, shorted, or chafed bus wiring to the fuel pump control module, Corroded or loose module connector / poor ground, Blown fuse / lost power feed, Low battery voltage, Failed fuel pump control module. The specific cause varies by vehicle.
How much does it cost to fix U0109?
Repair costs for U0109 range from $250 to $1,400, depending on the vehicle and root cause.
Which vehicles are affected by U0109?
Au7o has documented U0109 across 2 vehicle models from 2 manufacturers: Buick, Chevrolet.
Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.