P2632: Fuel Pump B Control Circuit Open
What to do
If the car hesitates, loses power or cuts out when the tank gets low — and is perfectly fine again after filling up — say exactly that, because it is very nearly the whole diagnosis.
Many vehicles have a tank built in two halves, moulded around a propshaft or exhaust, with the main pump in one half and a second pump to move fuel across from the other. When that second pump fails, the car empties one half and starves while the other half is still full. You genuinely run out of fuel with fuel in the tank.
Note which point on the gauge it happens at, and whether cornering, braking or a hill brings it on — both are useful. This is worth pressing, because the complaint gets investigated as a failing main pump, a blocked filter or a sensor, and all of those will test perfectly, since none of them is the problem. In the meantime, keeping the tank above half will usually avoid it entirely.
What this code means
An open circuit in the control of the second fuel pump.
Most cars have one fuel pump, so the first question is what a second one is doing there — and the commonest answer is a shape problem rather than a capacity one.
A fuel tank has to fit around whatever else is under the floor. On a vehicle with a propshaft, a rear differential or an exhaust running beneath it, the tank is moulded in two lobes joined by a narrow bridge — a saddle tank, straddling the obstruction. The pump can only sit in one lobe. Fuel in the other lobe has to be moved across, and that is what the second pump does: a small transfer pump, or on many designs a jet pump driven by returning fuel, lifting fuel over the bridge into the lobe the main pump draws from.
The consequence of losing it is the most distinctive symptom in this part of the corpus: the car runs out of fuel with a tank that is half full. The main pump empties its own lobe, the other lobe stays full, and the engine starves. Filling up cures it instantly and completely — which is exactly what makes it so hard to catch, because the fault disappears the moment anyone investigates it.
The pattern is unmistakable once it is described: the engine cuts out, hesitates or loses power when the gauge falls to roughly half or a quarter, always at that point, and always cured by refuelling. Cornering, braking or a hill often triggers it, because fuel sloshes away from the pump pickup and the reserve that would have covered it is stranded on the wrong side. A driver who reports this is describing a transfer pump, and the diagnosis is largely done.
The reason it costs money is that this is not what anyone looks for. Intermittent starvation on a car with fuel in it is investigated as a failing main pump, a blocked filter, a crank sensor or a relay — and every one of those tests fine, because every one of them is fine.
On other vehicles a second pump means something else entirely: a low-pressure lift pump feeding a high-pressure pump, or a second in-tank pump brought in only under high demand. Establishing which arrangement a vehicle has is the first step, because it changes the symptom completely.
Likely causes
Start here
- Open circuit in control wiring · moderate
- Faulty fuel transfer pump · moderate
- Corroded or loose connector · easy
Less common
- Blown fuse or failed supply · easy
- Damaged wiring harness · moderate
- Faulty fuel pump control module · specialist
Symptoms
Components involved
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
Be the first to write this up
Nothing posted about this yet. Whatever you found is worth writing down — even a dead end saves someone the same afternoon.
What makes one worth reading:
- The car — make, model, year and engine. The same fault behaves differently on each.
- What you measured, not only what you replaced.
- What actually fixed it — or that nothing did, which is worth knowing too.
Sign in or create an account to add what you found about P2632.