Cause
Faulty auxiliary transmission fluid pump
The electrically driven pump that holds transmission line pressure while the engine is stopped has failed. This is a separate part from the engine-driven main pump, and confusing the two matters: the main pump wearing out gives a car that slips everywhere, while this one failing gives a car that is perfect on the move and awkward from a standstill.
The failures are ordinary for a small brushless motor. The winding goes open or shorts, a bearing stiffens until the motor draws more current than its driver allows, or the integrated control electronics fail. Debris circulating in old fluid finds this pump readily, because it is smaller and tighter than the main one.
Two things are worth establishing before it is replaced. First, whether it is actually being fed — a pump with no supply is indistinguishable from a failed pump, and a fuse, relay or connector is a fraction of the price. Second, whether it is failing or simply losing a race: a pump asked to hold pressure against an internal leak runs far longer and harder than it was designed to, so it eventually fails because of the leak. Fitted to a transmission that still leaks, the new one goes the same way.
On many designs the pump and its control module are one assembly, so "replace the module" and "replace the pump" turn out to be the same job — worth asking before comparing quotes.
Typically specialist work. Needs equipment or training most home workshops do not have.
Codes this can cause (55)
Codes where this is a likely explanation first, rather than merely a possible one.
- P0B00 Electric/Auxiliary Transmission Fluid Pump Motor Phase U Current Likely for this code High
- P0B02 Electric/Auxiliary Transmission Fluid Pump Motor Phase U Current High Likely for this code Moderate
- P0B03 Electric/Auxiliary Transmission Fluid Pump Motor Phase V Current Likely for this code High
- P0B05 Electric/Auxiliary Transmission Fluid Pump Motor Phase V Current High Likely for this code Moderate
- P0B06 Electric/Auxiliary Transmission Fluid Pump Motor Phase W Current Likely for this code High
- P0B08 Electric/Auxiliary Transmission Fluid Pump Motor Phase W Current High Likely for this code Moderate
- P0B0D Electric/Auxiliary Transmission Fluid Pump Motor Control Module Likely for this code High
- P0C1B Electric/Auxiliary Transmission Fluid Pump Control Module Internal Temperature Too High Likely for this code High
- P0C1C Electric/Auxiliary Transmission Fluid Pump Control Module Internal Temperature Sensor Circuit Likely for this code Moderate
- P0C1D Electric/Auxiliary Transmission Fluid Pump Control Module Internal Temperature Sensor Circuit Range/Performance Likely for this code Moderate
- P0C1E Electric/Auxiliary Transmission Fluid Pump Control Module Internal Temperature Sensor Circuit Low Likely for this code Moderate
- P0C1F Electric/Auxiliary Transmission Fluid Pump Control Module Internal Temperature Sensor Circuit High Likely for this code Moderate
- P0C20 Electric/Auxiliary Transmission Fluid Pump Phase U-V-W Circuit/Open Likely for this code High
- P0C21 Electric/Auxiliary Transmission Fluid Pump Phase U-V-W Circuit Low Likely for this code Moderate
- P0C22 Electric/Auxiliary Transmission Fluid Pump Phase U-V-W Circuit High Likely for this code Moderate
- P0C26 Electric/Auxiliary Transmission Fluid Pump A Motor Current Likely for this code High
- P0C27 Electric/Auxiliary Transmission Fluid Pump A Motor Current Low Likely for this code Moderate
- P0C28 Electric/Auxiliary Transmission Fluid Pump A Motor Current High Likely for this code Moderate
- P0C29 Electric/Auxiliary Transmission Fluid Pump A Driver Circuit Performance Likely for this code High
- P0C2A Electric/Auxiliary Transmission Fluid Pump A Motor Stalled Likely for this code High
- P0DE4 Electric/Auxiliary Transmission Fluid Pump A Motor Over Temperature Likely for this code High
- P276A Electric/Auxiliary Transmission Fluid Pump B Motor Supply Voltage Circuit/Open Likely for this code Moderate
- P276B Electric/Auxiliary Transmission Fluid Pump B Motor Supply Voltage Circuit Low Likely for this code Moderate
- P276C Electric/Auxiliary Transmission Fluid Pump B Motor Supply Voltage Circuit High Likely for this code Moderate
- P276D Electric/Auxiliary Transmission Fluid Pump B Motor Current Likely for this code Moderate
Information, not instruction
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