Fuel pump failure (RepairPal). Fuel pump control module failure (RepairPal). Wiring problems (RepairPal). Lost communication between the engine control module and the fuel pump control module, often with U0074 or U18A2 set, on 2014-2018 GM trucks and SUVs (GM PIP5427B). A fuel pressure sensor that does not read the low end of its range, when P018B is also set, on 2014-2019 GM trucks and SUVs (GM PIP5286B). A fuel feed pipe restricted by debris on 2021-2023 GM full-size trucks and SUVs with the 5.3L or 6.2L engine (GM bulletin 22-NA-220).

Repair the communication fault between the engine control module and fuel pump control module first, when communication codes are set (GM PIP5427B). Replace the fuel pump if testing confirms low flow; RepairPal lists this as the common repair. Replace the fuel pump control module if it has failed (RepairPal). Repair damaged wiring or connectors (RepairPal). Replace the fuel pressure sensor if it fails GM's depressurize test, with a new O-ring ordered separately (GM PIP5286B). On covered 2021-2023 GM models, replace the fuel feed pipe if the P2635 diagnostic does not find another cause (GM bulletin 22-NA-220).

P2635⛽ Fuel delivery (fuel pump and fuel pump control module)Stop and fix promptly

P2635: Fuel Pump A Low Flow/Performance (Meaning, Causes, Fixes)

Q: What does P2635 mean?

P2635 means the actual fuel pressure does not match the pressure the computer commanded from fuel pump "A". RepairPal lists a failed fuel pump, a failed fuel pump control module and wiring problems as causes. GM bulletins add that on many 2014-2019 Silverados, Sierras, Tahoes and Yukons a communication fault between the engine computer and the fuel pump control module, or a bad fuel pressure sensor, can set it, and that on 2021-2023 models debris in the fuel feed pipe can. On many newer vehicles a fuel pump control module runs the fuel pump at different speeds to hold a target fuel pressure. RepairPal explains that the module works out the fuel pressure the engine needs, commands the pump to deliver it, and sets P2635 when the actual pressure does not meet the commanded pressure. The code name says "Low Flow/Performance", but GM's preliminary information PIP5427 describes cases on 2014-2018 GM trucks and SUVs where the low-pressure fuel system actually read substantially higher than desired, caused by lost communication between the engine control module and the fuel pump control module (codes U0074 or U18A2 set too). So the sources differ on where to look first: RepairPal's common repair is replacing the fuel pump, while GM says to fix any communication codes first, warns that replacing the fuel pump module or other fuel system parts typically will not fix a pressure-too-high case, and in PIP5286B points to a fuel pressure sensor that does not read the low end of its range when P2635 is set with P018B. P2636 is the matching code for fuel pump "B".

Q: Can I keep driving with P2635?

Stop and fix promptly. Get it checked soon. RepairPal rates P2635 as Urgent, and on 2021-2023 GM trucks and SUVs GM says it can come with a Reduced Engine Power message. If the fuel pump really cannot keep up, the engine can lose power or stall, which is dangerous in traffic. If the engine hesitates, stalls or goes into reduced power, limit driving and have it diagnosed before a long trip.

Reviewed 2026-10-23 · Based on 4 cited source(s)

What P2635 means

On many newer vehicles a fuel pump control module runs the fuel pump at different speeds to hold a target fuel pressure. RepairPal explains that the module works out the fuel pressure the engine needs, commands the pump to deliver it, and sets P2635 when the actual pressure does not meet the commanded pressure. The code name says "Low Flow/Performance", but GM's preliminary information PIP5427 describes cases on 2014-2018 GM trucks and SUVs where the low-pressure fuel system actually read substantially higher than desired, caused by lost communication between the engine control module and the fuel pump control module (codes U0074 or U18A2 set too). So the sources differ on where to look first: RepairPal's common repair is replacing the fuel pump, while GM says to fix any communication codes first, warns that replacing the fuel pump module or other fuel system parts typically will not fix a pressure-too-high case, and in PIP5286B points to a fuel pressure sensor that does not read the low end of its range when P2635 is set with P018B. P2636 is the matching code for fuel pump "B".

Severity: can I keep driving?

Stop and fix promptly

Get it checked soon. RepairPal rates P2635 as Urgent, and on 2021-2023 GM trucks and SUVs GM says it can come with a Reduced Engine Power message. If the fuel pump really cannot keep up, the engine can lose power or stall, which is dangerous in traffic. If the engine hesitates, stalls or goes into reduced power, limit driving and have it diagnosed before a long trip.

Common symptoms

Check engine light on (GM bulletins)
Decreased engine performance (RepairPal)
Reduced Engine Power message on the driver information display on some 2021-2023 GM models (GM bulletin 22-NA-220)
The light may come on and then turn off with no drivability problem (GM bulletin 22-NA-220)

Likely causes

Roughly most to least common, based on the sources below. Your vehicle may differ.

Fuel pump failure (RepairPal)
Fuel pump control module failure (RepairPal)
Wiring problems (RepairPal)
Lost communication between the engine control module and the fuel pump control module, often with U0074 or U18A2 set, on 2014-2018 GM trucks and SUVs (GM PIP5427B)
A fuel pressure sensor that does not read the low end of its range, when P018B is also set, on 2014-2019 GM trucks and SUVs (GM PIP5286B)
A fuel feed pipe restricted by debris on 2021-2023 GM full-size trucks and SUVs with the 5.3L or 6.2L engine (GM bulletin 22-NA-220)

Diagnostic steps you can do

⚠ Before you start

Work on a cool engine, parked on level ground with the parking brake set. Never work under a car supported only by a jack.

Read all stored codes. If U0074, U18A2 or other communication codes are set, GM says to diagnose those first, before P2635.
Note whether P018B (fuel pressure sensor) is also set; GM links that combination to a fuel pressure sensor that reads wrong.
With a scan tool that shows live data, compare desired and actual fuel pressure. GM says that if actual pressure reads 10 psi or more above desired, replacing the fuel pump module or fuel parts typically won't fix it.
Check the fuel pump and fuel pump control module fuses, connectors and wiring for corrosion or damage.
Check for technical service bulletins for your vehicle, especially on 2014-2023 Chevrolet, GMC and Cadillac full-size trucks and SUVs.

Typical fixes

Repair the communication fault between the engine control module and fuel pump control module first, when communication codes are set (GM PIP5427B)
Replace the fuel pump if testing confirms low flow; RepairPal lists this as the common repair
Replace the fuel pump control module if it has failed (RepairPal)
Repair damaged wiring or connectors (RepairPal)
Replace the fuel pressure sensor if it fails GM's depressurize test, with a new O-ring ordered separately (GM PIP5286B)
On covered 2021-2023 GM models, replace the fuel feed pipe if the P2635 diagnostic does not find another cause (GM bulletin 22-NA-220)

Repair costs vary widely by vehicle, region, parts brand and shop, so we don't quote prices. Get a written estimate after diagnosis.

🛠 When to call a pro

The engine stalls, hesitates or goes into reduced power
Communication codes such as U0074 or U18A2 are set along with P2635
You smell fuel or see a fuel leak
You have no scan tool that shows desired and actual fuel pressure

Where to buy

Plain search links. Always match parts to your exact year, make, model and engine.

OBD2 scanners on Amazon Parts at Advance Auto Parts catalog at RockAuto

FAQs

Is P2635 serious?

RepairPal rates it Urgent. A fuel pump that can't keep up can cause power loss or stalling, and GM says some trucks show Reduced Engine Power with this code, so get it diagnosed soon.

Does P2635 always mean a bad fuel pump?

No. RepairPal's common repair is a fuel pump, but GM bulletins say a communication fault between the engine computer and the fuel pump control module, a bad fuel pressure sensor, or a debris-restricted fuel feed pipe can also set it on some GM trucks and SUVs.

What is P2635 on a Chevy Silverado?

On 2014-2018 Silverados, GM says to fix any U0074 or U18A2 communication codes first, since lost communication with the fuel pump control module can set P2635. On 2021-2023 Silverado 1500s with the 5.3L or 6.2L, GM bulletin 22-NA-220 says debris in the fuel feed pipe can cause it.

How much does it cost to fix P2635?

None of the sources gives a repair cost. It depends on whether the fix is wiring, a sensor, the control module or the fuel pump itself, so get a diagnosis and a written estimate.

Sources

Last reviewed 2026-10-23. Code definitions and repair steps can vary by manufacturer. Confirm with your vehicle's service information.