P2635: Fuel Pump A Low Flow/Performance
A generic powertrain (engine and transmission) trouble code, same meaning on every brand.
Short, gentle trips only - low fuel flow shows up exactly when demand peaks: hills, merges, full throttle. Plan around the stumble happening at the worst time, because it will.
Symptoms
- Stumble or power loss under load or uphill
- Long cranking when hot
- Stalling at speed in advanced cases
- Whining pump on some cars
Likely causes, most common first
- Fuel pump worn below its flow spec
- Clogged fuel filter or strainer
- Restricted or kinked fuel line
- Voltage drop starving the pump motor
Read P2635 yourself before paying for diagnosis
A basic Bluetooth OBD-II scanner ($20-40) plugs into the port under the dashboard and shows this code with live sensor data on your phone - useful both for confirming the fix and for talking to a shop from an informed position.
What is going on and how it gets diagnosed
P2635 says the computer measured the fuel pump's real-world delivery - through pressure behavior, commanded duty, or both - and found it short of specification. Unlike a circuit code, this one is about hydraulics: something between tank and rail cannot keep up when the engine drinks hardest.
The suspects line up by price. A filter or in-tank strainer clogged by years of sediment is the cheap and surprisingly common ending, especially on cars that ran low tanks habitually - sediment lives at the bottom, and low-fuel driving feeds it to the strainer. Voltage drop is the sleeper: a corroded pump connector steals a volt or two, and pump flow falls with voltage. Only after a proper pressure-and-volume test convicts it should the pump itself - the expensive, drop-the-tank item - be sentenced. Symptom management until repair is simple and real: keep the tank above a quarter, and keep off roads where a stumble at full throttle is dangerous.
Repair options and cost
Typical US independent-shop ranges, parts and labor. Dealers run higher; regional labor rates vary.
Owner reports mentioning P2635
“Engine stalling, a rough-running engine, reduced power mode (sluggish acceleration), a "Check Engine" light, or the vehicle failing to start. It started puttering really bad and died in the middle of the intersection. Check engine light came on. I got it to start, was really hard start and puttered bad then it died again and then I got it to start again, was a really hard start and puttered and died again. I was able to start it again get in the driveway but couldn't go very fast. Check engine codes present are P2635 and P018B”2017 GMC Yukon XL · Mar 2026
“2015 gmc Acadia, vin ending 7457,p2635,stuttering/hesitation and engine stalling when Arizona temperatures exceed 100* f , and mechanic advising that the condition corresponded to a known gmc issue for which they could not obtain an applicable corrective part / repair”2015 GMC Acadia · Jun 2025
“The vehicle just turned off and locked up while driving and the check engine light was on that presented Code P2635 and P018B”2019 Chevrolet Tahoe · Mar 2024
Show 5 more owner reports
“Code: P2635 Fuel pump 'A' low flow/ performance It only happens when it's warm outside. It was doing this last summer and during the winter it stopped now it's 80 degrees + outside it's throwing the code again”2017 Chevrolet Silverado 1500 · Feb 2024
“This vehicle is owned by the City of Fort Lauderdale Police Department. We are submitting complaints for multiple Tahoe's that have stopped during operation causing extreme danger to our staff and other drivers in the city. The cause is always bad fuel pumps and our units have had to have the pumps replaced in some cases multiple times. 7-12-23 Stalled in intersection and turned off Engine wont start Will start again after several minutes CHECK UNIT CODE P2635 PINPOINT TEST NEED FUEL PUMP 2-12-24 Sputters and stalls and stumbles CHECK UNIT NO ENGINE LIGHT AND NO CODES. REPLACE FUEL PUMP DRIVER MODULE”2019 Chevrolet Tahoe · Jul 2023
“This vehicle is owned by the City of Fort Lauderdale Police Department. We are submitting complaints for multiple Tahoe's that have stopped during operation causing extreme danger to our staff and other drivers in the city. The cause is always bad fuel pumps and our units have had to have the pumps replaced in some cases multiple times. 03-04-24 Engine sputtering Scanned vehicle and codes P2635 fuel pump low fuel/performance was detected. Ordered fuel pump and fuel pump module.”2019 Chevrolet Tahoe · Mar 2023
“My 2015 Malibu continues to have problems. I have a constant P Code (P2635) that refers to the fuel pump (Low Performance). The Malibu has the auto stop but at times the vehicle wants to lunge forward. It also at a stop not only goes to the auto stop (engine ) but cut off all the way . Which this result in having to place the car back in park to re-start. I have seen a youtube video of a hotspot (wear) on the wiring harness that is located in the right rear fender well that this blue and white wire was worn and broken possible causing this problem. Other that this issue the vehicle is good and still gets around 35mpg.”2015 Chevrolet Malibu · Sep 2021
“After long periods of running and idle, vehicle stalls out has a hard time restarting. Gas paddle being press helps sometimes. Check code p2635 plus others (random secondary codes), come on. This has taken place in az where the ambient air temperature typically is over 100. Vehicle has been to gm dealer who says its vaporizing the fuel in the lines. Tsb pip5507b dose not include 2018, however the design hasn't changed. Conditions; long idle, hot weather, low speeds under 25 mph or idle. Location; az sonrona dessert, off-road, jobsite, city streets.”2018 GMC Sierra 1500 · Jul 2020 · 35,692 mi
Cars that report P2635 most often
Based on mentions of this code in NHTSA owner complaints.
Frequently asked questions
Can I drive with P2635?
Short, gentle trips only - low fuel flow shows up exactly when demand peaks: hills, merges, full throttle. Plan around the stumble happening at the worst time, because it will.
How much does it cost to fix P2635?
Typical US repair costs range from $50 for the simplest fix (fuel filter replacement where serviceable) to $1,000 in the worst case. The right number depends on which cause your car has - see the causes list.
Related codes
The codes closest to P2635. They often appear together, and telling them apart is usually what narrows the diagnosis.
Definition per SAE J2012 standard nomenclature. Symptoms, causes and costs are editorial guidance - always confirm with a diagnosis of your specific vehicle.