What does it mean?
Fuel pump module B is connected and its control circuit is electrically alive, but the way it behaves does not match what the module commanded. The control unit compares the commanded pump output with the feedback it gets, which may be current draw, a speed or duty feedback signal, or the fuel pressure that results, and stores this code when the difference stays outside tolerance. In other words the circuit is neither open nor shorted, it simply is not performing. Typical findings are added resistance in the supply or ground path, a tired pump that draws the wrong current, or a restriction that makes the pump work against an abnormal load. Fuel delivery is often still adequate at light load, so the complaint may only appear when the engine asks for maximum flow.
Symptoms
- MIL on, sometimes together with fuel pressure or lean mixture codes
- Power loss or hesitation at high load, while light throttle driving feels normal
- Extended cranking, particularly after the vehicle has stood for a while
- Occasional stumble or surge under heavy acceleration
- Whining noise from the tank area when the pump is struggling
- Fuel pressure in live data that lags behind the commanded value
Likely causes
- High resistance in the pump supply or ground circuit from corroded terminals or a partly damaged wire
- Worn pump drawing abnormal current for the commanded output
- Restricted fuel filter or a blocked in-tank strainer making the pump work against excessive pressure
- Incorrect or non-matching replacement pump with different electrical characteristics
- Corrosion or moisture in the tank flange connector affecting the feedback signal
- Failing pump driver module that cannot hold the commanded output
- Low system voltage or a weak battery affecting pump performance
- Kinked or restricted fuel line downstream of the pump
How to fix it
- Look at the commanded pump output and the feedback value side by side in live data during idle and a hard acceleration
- Measure fuel pressure with a gauge and compare it with the value the module reports
- Perform voltage drop tests on the pump supply and ground while the pump is running under load
- Measure pump current draw and compare it with specification; both high and low readings are meaningful
- Replace or inspect the fuel filter and check the in-tank strainer for blockage
- Inspect the tank flange connector for corrosion and confirm all terminals are tight
- Renew the pump or driver module only after the circuits and the restriction checks are complete, then verify pressure and feedback follow the command