P0C29: Electric/Auxiliary Transmission Fluid Pump A Driver Circuit Performance
What to do
One of the few places the electronics really are the likely answer — but only after the pump's windings and supply have been measured and found good. Ask whether the driver is separate from the pump on this model; often it is not.
What this code means
The output stage driving the auxiliary pump is not behaving as it should — commanded correctly, supplied correctly, and producing the wrong result.
This is the driver rather than the motor or the command line, and the corpus's standing advice not to blame electronics is deliberately relaxed here on the P0964 test: a driver stage is genuinely at fault when its circuits report faults and the motor's windings measure correctly. Establish the second half before accepting the first.
Note that on many designs the driver is integrated with the pump, so "replace the driver" and "replace the pump" are one job — worth asking before quotes are compared.
Likely causes
Start here
- Faulty auxiliary transmission fluid pump · specialist
Less common
- Corroded or loose connector · easy
- Low system voltage · moderate
- Water ingress into connector · easy
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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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.
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