What it means
The second fuel pump runs but does not deliver expected volume or pressure. Worn pump, restricted filter, or leaking pressure regulator.
At a glance
- Usually lights the check-engine light
How it works
Fuel Pump B is the secondary pump stage, and the module checks whether it supplies the expected fuel volume or pressure when operating. P2636 sets when Pump B runs but its delivery remains too low, which can result from a worn impeller, restricted filter, or regulator leakage.
Common causes
Most likely first.
- Worn impeller reduces volumetric efficiency
- Restricted in-tank or in-line fuel filter
- Pressure regulator leaks back to tank
Symptoms
- Check engine light on
- Hard start, no start, or stalling under load
- Power loss especially at high load or rpm
- Possible long cranking time
How to diagnose it
- Record freeze-frame data and review Pump B command, fuel pressure, and related fuel-pressure or trim codes.
- Inspect Pump B wiring and its fuel lines and connectors for leaks, damage, or restrictions.
- Check the serviceable filter or strainer in the Pump B supply path for blockage according to the vehicle's service information.
- Measure Pump B pressure and flow using the specified procedure, including under the operating conditions that trigger the fault.
- If delivery remains low, test the regulator for leakage and verify Pump B's electrical supply against the manufacturer's specification.
Common fixes
- Replace a restricted serviceable filter or strainer in the Pump B supply path.
- Repair a leaking or restricted line or a poor electrical connection to Pump B.
- Replace the regulator if testing confirms it leaks or fails to maintain pressure.
- Replace Pump B if its measured flow or pressure remains below specification with a clear supply path.
Can I keep driving?
Limit driving and avoid heavy loads, since low Pump B delivery can cause hesitation, power loss, or stalling when demand rises. If the engine stalls or will not maintain power, stop and arrange recovery.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.