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DTC codes / P0Cxx · Hybrid propulsion / P0C26

P0C26Electric/Auxiliary Transmission Fluid Pump A Motor Current

P0C26 indicates that the transmission control module (TCM) has detected an out-of-range current draw in the electric auxiliary transmission fluid pump A motor circuit. The TCM monitors the pump motor's current and flags this code when the current is higher or lower than expected, or when the circuit is open or shorted.

SystemPowertrain
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyIntermediate
AreaHybrid propulsion

Symptoms you may notice

  • Illumination of the malfunction indicator lamp (MIL) on the dashboard
  • Often no symptoms besides the warning light, especially if the auxiliary pump is only used during engine stop-start events
  • Transmission may enter limp mode or fail to engage drive or reverse
  • Harsh or delayed shifting, particularly when the engine restarts after an auto-stop
  • Overheating of the transmission fluid during prolonged idling or stop-and-go traffic
  • Reduced fuel economy due to the pump running continuously or not at all

Common causes, most likely first

  1. Faulty auxiliary transmission fluid pump motor (worn brushes, shorted windings, or internal damage)
  2. Damaged or corroded wiring harness or connector at the pump motor
  3. Blown fuse or faulty relay supplying power to the pump motor circuit
  4. Failed transmission control module (TCM) or pump control module
  5. Restricted or contaminated transmission fluid causing excessive pump load
  6. Poor ground connection for the pump motor circuit

How to diagnose and fix it

  1. Verify the battery voltage and inspect the pump motor fuse and relay; replace any blown fuse or faulty relay
  2. Disconnect the pump motor connector and inspect terminals for corrosion, tightness, and signs of overheating
  3. Measure resistance across the pump motor terminals and compare to the manufacturer's specification; replace the motor if out of range
  4. Check the wiring harness for continuity, shorts to ground, and shorts to power between the TCM and the pump motor
  5. Test the pump motor by applying fused 12-volt power directly to confirm operation
  6. If the motor and wiring test good, diagnose the TCM or pump control module for internal faults
  7. Clear the code and perform a road test with stop-start activation to verify the repair

Before you replace the auxiliary pump

  • A weak or failing battery often causes this code because the auxiliary pump draws high current during engine restarts, and low system voltage can mimic a motor fault.
  • Corroded ground straps between the transmission and the chassis are a commonly overlooked cause of intermittent P0C26.
  • The code can set if the transmission fluid is overfilled or contaminated, increasing pump load beyond the expected current range.
  • Some vehicles use the auxiliary pump only during auto-stop events, so a failed pump may not affect normal driving until the stop-start system activates.
  • After replacing the pump motor, some TCMs require a relearn or adaptation procedure to prevent the code from returning.

Can I keep driving with P0C26?

You can usually drive the vehicle short distances to a repair shop, but avoid heavy traffic, prolonged idling, and stop-start driving that activates the auxiliary pump. If the transmission enters limp mode or the vehicle fails to move, stop driving and seek professional assistance.

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.

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