What Does P0C1B Mean?
DTC P0C1B indicates that the internal temperature of the auxiliary transmission fluid pump control module has exceeded its maximum allowable operating temperature. This pump maintains hydraulic pressure in the transmission when the engine is off (in hybrids) or provides continuous fluid circulation in EVs with geared transmissions. Overheating of the control module can cause pump shutdown, leading to loss of transmission lubrication and hydraulic pressure.
Common Causes
25%
Control module mounted in a location with poor heat dissipation or airflow
25%
Pump running continuously at high speed due to low transmission fluid level
20%
Failed cooling provision for the pump controller (heat sink or fan)
15%
Excessive ambient or underhood temperature during operation
15%
Internal MOSFET degradation in the pump driver circuit causing increased losses
Diagnostic Steps
1
Step 1: Review freeze-frame data for the pump module internal temperature, pump duty cycle, transmission fluid temperature, and ambient temperature at the time of fault.
2
Step 2: Check the transmission fluid level and condition. Low fluid forces the pump to work harder, generating more heat. Top off or replace as needed.
3
Step 3: Inspect the pump control module mounting location for adequate heat sinking and airflow. Ensure no insulation, debris, or shields are blocking heat dissipation.
4
Step 4: Check for related DTCs (P0C1C–P0C1E) that may indicate the temperature sensor circuit is faulty, causing false over-temperature readings.
5
Step 5: Monitor the pump duty cycle in real-time. If the pump is commanded to full speed continuously, investigate why — this typically indicates a hydraulic leak, low fluid, or a pressure control issue.
Estimated Repair Cost
$300 - $2,000
Parts + labor, varies by vehicle and location
DTC P0C1B indicates that the internal temperature of the auxiliary transmission fluid pump control module has exceeded its maximum allowable operating temperature. This pump maintains hydraulic pressure in the transmission when the engine is off (in hybrids) or provides continuous fluid circulation ...
The most common cause of P0C1B (Auxiliary Transmission Fluid Pump Control Module Internal Temperature Too High) is: Control module mounted in a location with poor heat dissipation or airflow
Typical repair costs for P0C1B range from $300 to $2,000, depending on the vehicle, location, and whether you do it yourself or go to a shop.
If the auxiliary pump overheats and shuts down, the transmission loses hydraulic pressure during EV-only driving, potentially causing gear disengagement, loss of drive, or transmission damage from insufficient lubrication.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0C1B to identify the root cause.
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Quick Info
Category
Powertrain
System
Hybrid/EV Transmission Auxiliary Pump
Difficulty
Type
Generic (SAE)
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