P0B0C: Electric/Auxiliary Transmission Fluid Pump A Hydraulic Leakage
What to do
The pump is almost certainly not what is wrong, even though the code names it — the leak is inside the gearbox and the pump is what noticed. If a pump replacement is quoted, ask what is leaking and how that was established; a pump fitted to a leaking transmission fails again. Fluid condition and level are the first things to check and the cheapest. Acting early matters here: running the pump against a leak is what eventually kills the pump too.
What this code means
The pump is running and pressure is still falling. Nothing is wrong with the motor, the wiring or the supply — the module has commanded pressure, watched the pump deliver it, and seen it leak away faster than the pump can replace it.
This is the most misread code in the family, because it names the pump and the pump is not the fault. A leak the pump cannot keep up with is inside the transmission — a hardened seal, a worn valve-body bore, a check ball not seating, clearance opened up by wear. The pump is the instrument that detected it, in exactly the way P0700 is the transmission asking for a lamp rather than a failed gearbox. Replacing the pump on this code fixes nothing and the code returns.
And the second failure is caused by the first. A pump asked to hold pressure against a leak runs far longer and far harder than it was designed to — the argument written out at P0943, where cycling frequency puts a number on a leak. So a leak left alone eventually does destroy the pump, and by then the bill is both parts. That is an argument for acting early rather than for replacing the pump now.
Likely causes
Start here
- Internal transmission leak · specialist
- Low or degraded transmission fluid · easy
Less common
- Low transmission line pressure · specialist
- Worn transmission fluid pump · specialist
- Debris in the transmission fluid · 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
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