P0DE4: Electric/Auxiliary Transmission Fluid Pump A Motor Over Temperature
What to do
You may notice the engine no longer switches off at junctions, and fuel consumption rising. Have the transmission fluid level and condition checked first — that is the commonest cause and the cheapest. Do not ignore it; running a gearbox on low pressure damages it.
What this code means
The electric transmission fluid pump's motor has exceeded its temperature limit.
The pump exists because a hybrid switches its engine off, and the whole family at P0B00 turns on that one fact. A conventional automatic gearbox is pressurised by a pump driven off the engine; stop the engine and the pressure disappears along with it. A hybrid that stops its engine at every set of lights therefore needs an electric pump to hold pressure while the engine is not running — and that is why a fault here is invisible on a road test with the engine going.
Over temperature specifically points at the pump working harder than it should, which has three ordinary causes worth separating. The fluid may be low or degraded, so the pump moves less of it and what it moves carries away less heat. The pump may be failing mechanically, with worn bearings raising the current it draws. Or it is being asked to run far more than it was designed to — a leak inside the gearbox that it is quietly compensating for, which is the P0B0C pattern and the one where replacing the pump fixes nothing.
A pump that overheats will be shut down to protect itself, and on a hybrid that means the engine has to keep running to maintain gearbox pressure, so the visible symptom is a car that has stopped switching its engine off.
Likely causes
Start here
- Low or degraded transmission fluid · moderate
- Faulty auxiliary transmission fluid pump · specialist
Less common
- Debris in the transmission fluid · moderate
- Corroded or loose connector · specialist
- Damaged wiring harness · 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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