Fuel Pump "A" Low Flow / Performance
The DURAMAX-P2635 (Duramax) diesel fault code means: Fuel Pump "A" Low Flow / Performance. This is a serious severity code.
- Keep driving?
- Yes, with caution
- DIY difficulty
- intermediate
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What Are the Symptoms of DURAMAX-P2635?
- Check Engine Light on
- Hard starting or long cranking
- Loss of power under load
- Possible stalling
What Causes DURAMAX-P2635? (Most Likely First)
- Weak or failed fuel pump High
- Restricted fuel filter or pickup High
- Poor power or ground to the pump Moderate
- Air in the fuel supply Moderate
Can I Still Drive with DURAMAX-P2635?
Yes, with caution. DURAMAX-P2635 is rated serious severity. Keep trips short and get it diagnosed soon rather than waiting for symptoms to worsen.
Frequently Asked Questions
What does P2635 mean on a Duramax?
P2635 means Fuel Pump "A" Low Flow / Performance. The engine computer has detected that fuel pump "A" is not delivering the flow or pressure it expects.
Is P2635 a Duramax-specific code?
No. P2635 is a generic OBD-II code defined by SAE J2012, so it means the same thing on any vehicle that sets it. The exact conditions GM uses to set it on its diesels are in GM service information.
Mechanics Guide Step-by-step diagnosis
How Do You Diagnose DURAMAX-P2635?
Find which pump is "A" on your truck in the service information.
Check supply pressure and flow against the specification.
Check pump voltage and ground under load, and inspect the fuel filter.
Sources 1
This page is built from documented references. Verify against your own service info before repair work.
- SAE J2012Diagnostic Trouble Code Definitions (defines P2635 as a generic OBD-II code)
P2635 on Other Platforms
The same code ID appears across other engines, vehicles, and equipment. Diagnostic flow varies by platform — see the matching breakdown:
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