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DTC codes / P0Cxx · Hybrid propulsion / P0C1F

P0C1FElectric/Auxiliary Transmission Fluid Pump Control Module Internal Temperature Sensor Circuit High

The electric auxiliary transmission fluid pump control module monitors its own internal temperature sensor, and code P0C1F is set when the signal circuit voltage rises above the expected range for a specified time. This indicates an open circuit, a short to voltage, or a failed sensor inside the control module, which can prevent the auxiliary pump from running and may affect transmission cooling or stop-start operation.

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

Symptoms you may notice

  • Illumination of the check engine light or service transmission message, often with no other noticeable symptoms.
  • The auxiliary transmission fluid pump may not activate during engine stop-start events, leading to reduced cooling or lubrication.
  • In some vehicles, the stop-start system may be disabled or the transmission may enter a limp mode.
  • A stored code P0C1F is present when scanning the transmission control module (TCM) or auxiliary pump control module.
  • Possible delayed engagement or harsh shifting if the auxiliary pump is used for main line pressure during certain conditions.

Common causes, most likely first

  1. An open circuit or high resistance in the temperature sensor signal wire between the sensor and the control module.
  2. A short to voltage on the sensor signal circuit, often due to chafed wiring or connector contamination.
  3. A faulty internal temperature sensor inside the auxiliary transmission fluid pump control module.
  4. Corroded, loose, or water-intruded electrical connectors at the pump control module or transmission harness.
  5. A failed control module internal circuit that misinterprets the sensor signal as high.
  6. In rare cases, a low or unstable reference voltage supply to the sensor causing erratic high readings.

How to diagnose and fix it

  1. Verify the code with a scan tool and check for any related codes in the transmission control module (TCM) and auxiliary pump control module.
  2. Inspect the wiring harness and connectors at the auxiliary pump control module for signs of damage, corrosion, or loose pins.
  3. Measure the resistance of the internal temperature sensor circuit with a multimeter and compare to the manufacturer's specification if available.
  4. Backprobe the sensor signal circuit to check for a short to voltage or an open circuit while wiggling the harness.
  5. If the wiring and connectors are good, test the control module with a known-good unit or perform a module swap to confirm internal sensor failure.
  6. Replace the auxiliary transmission fluid pump control module if the internal sensor is confirmed faulty, then clear codes and verify the repair.
  7. Perform a road test to ensure the stop-start system and transmission cooling functions operate correctly and the code does not return.

Hidden Causes of P0C1F You Should Not Overlook

  • A common misdiagnosis is replacing the auxiliary pump control module when the real problem is a chafed signal wire near the transmission mount or a corroded connector pin.
  • The code can set intermittently due to temperature-related resistance changes in the sensor, so a wiggle test and freeze-frame data review are essential before condemning parts.
  • Some vehicles use the auxiliary pump only during engine stop-start events, so the driver may never notice a performance issue even though the code is stored.
  • A low battery or charging system fault can cause unstable reference voltage and set this code falsely, so always check battery health and grounds first.
  • The internal temperature sensor is not serviceable separately on many units, meaning a confirmed sensor failure requires control module replacement.

Can I keep driving with P0C1F?

You can generally continue driving, but avoid relying on the stop-start system and monitor for any transmission warning messages. If the vehicle enters limp mode or you notice overheating, stop driving and seek professional diagnosis.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

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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