P2633: Fuel Pump B Control Circuit Low
What to do
Expect hesitation or cutting out once the tank falls below about half, cured by filling up — the pattern is explained at P2632. Keeping the tank topped up will usually avoid it until it is repaired.
One thing worth asking about when the work is done: what was found in the tank. A small pump at the bottom of a tank can be jammed by rust or debris that has settled there, and a new pump fitted into a dirty tank meets the same problem. It is a reasonable question and it occasionally saves the job being done twice.
What this code means
The second fuel pump's control circuit reads below its valid range — normally a short to ground, or a pump motor that has seized and dragged the circuit down. What the second pump does, and the half-full-tank symptom that follows losing it, is at P2632.
A seized motor is worth taking seriously as a cause rather than assuming a wiring fault, because a transfer pump lives at the bottom of a fuel tank and spends its life in whatever has settled there. Rust flakes from a steel tank, debris that came in with the fuel, and the residue of years of short journeys all end up in the same place, and a small pump is easier to jam than a large one.
That matters for the repair: if debris stopped the pump, a new pump in the same tank meets the same debris. Anyone opening the tank for this should look at what is in it.
Likely causes
Start here
- Wiring shorted to ground · moderate
- Faulty fuel transfer pump · moderate
- Seized pump motor · moderate
Less common
- Debris or corrosion inside the fuel tank · specialist
- Damaged wiring harness · moderate
Symptoms
Components involved
Information, not instruction
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Community experience
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