Open circuit or high resistance in the power or ground wire to the auxiliary transmission fluid pump control module; Short to voltage on the control circuit between the TCM and the pump control module; Faulty auxiliary transmission fluid pump control module; Corroded or damaged electrical connector at the pump or control module; Failed transmission control module (TCM) driver circuit; Blown fuse or relay supplying power to the auxiliary pump circuit

DTC codes / P0Cxx · Hybrid propulsion / P0C25

P0C25Electric/Auxiliary Transmission Fluid Pump Control Module Circuit High

P0C25 indicates that the electric or auxiliary transmission fluid pump control module has detected an abnormally high voltage on its control circuit, which typically points to an open circuit, a short to power, or a faulty module. The transmission control module (TCM) monitors this circuit and sets the code when the voltage exceeds the expected range for the commanded pump state.

SystemPowertrain

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyProfessional

AreaHybrid propulsion

Symptoms you may notice

Illumination of the check engine light or transmission warning light
Often no symptoms besides the warning light, especially if the auxiliary pump is only used during auto start-stop events
Harsh or delayed shifting as the transmission may enter limp mode
Reduced fuel economy due to the engine not entering start-stop mode
In rare cases, the vehicle may stall or hesitate when coming to a stop
Transmission may fail to engage drive or reverse immediately after a stop

Common causes, most likely first

Open circuit or high resistance in the power or ground wire to the auxiliary transmission fluid pump control module
Short to voltage on the control circuit between the TCM and the pump control module
Faulty auxiliary transmission fluid pump control module
Corroded or damaged electrical connector at the pump or control module
Failed transmission control module (TCM) driver circuit
Blown fuse or relay supplying power to the auxiliary pump circuit

How to diagnose and fix it

Verify battery voltage and inspect the auxiliary pump fuse and relay, replacing any blown fuse or faulty relay
Disconnect the pump control module connector and inspect for corrosion, water intrusion, or loose pins; clean or repair as needed
Measure resistance and voltage on the control circuit between the TCM and the pump control module to check for opens or shorts
Perform a voltage drop test on the power and ground circuits under load to identify high resistance connections
Swap the auxiliary pump control module with a known-good unit if available, then clear codes and retest
Check for technical service bulletins (TSBs) or software updates for the TCM that may address false setting of this code
If all circuits test good, diagnose or replace the TCM as the last step

Before you replace the auxiliary pump module

A common oversight is assuming the pump itself has failed when the real problem is a chafed wire harness near the transmission mount or a corroded ground connection.
The code can be set intermittently by a loose battery terminal or weak battery, so always load-test the battery and check charging system voltage first.
On vehicles with auto start-stop, the auxiliary pump may only run under specific conditions, so a circuit fault may not produce drivability symptoms until the system is commanded on.
A short to voltage on the control circuit can be caused by wiring routed too close to the exhaust or by aftermarket accessories improperly tapped into the harness.
Replacing the control module without clearing adaptive learning values can lead to harsh shifting that mimics a failed repair, so always perform a relearn procedure after replacement.

Can I keep driving with P0C25?

You can usually drive the vehicle short distances to a repair shop, but avoid heavy loads or long trips because the transmission may enter limp mode and the auxiliary pump may not function, potentially causing overheating in start-stop traffic. If the vehicle exhibits harsh shifting or stalling, stop driving and seek professional diagnosis.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.