What Does P0C23 Mean?
DTC P0C23 indicates an open circuit condition in the auxiliary transmission fluid pump control module wiring. The auxiliary pump is used in many modern automatic and hybrid transmissions to maintain fluid pressure when the engine is off or during electric-only driving. An open circuit means the control module cannot communicate with or energize the pump, potentially causing inadequate transmission lubrication and cooling under certain operating conditions.
Common Causes
35%
Broken or disconnected wiring harness to auxiliary pump control module
25%
Corroded or backed-out connector pins at the control module
20%
Failed auxiliary transmission fluid pump control module
12%
Blown fuse or open relay in the pump control circuit
8%
PCM/TCM driver circuit failure
Diagnostic Steps
1
Check all fuses and relays associated with the auxiliary transmission fluid pump circuit using a fuse tester or multimeter.
2
Locate the auxiliary pump control module connector and inspect for corrosion, bent pins, moisture intrusion, or disconnection.
3
Perform a continuity test on the wiring harness between the TCM/PCM and the auxiliary pump control module, checking each conductor for opens.
4
Measure supply voltage and ground at the control module connector with the key on to verify the module is receiving power.
5
If wiring and power supply check good, substitute a known-good auxiliary pump control module and retest.
Estimated Repair Cost
$150 - $800
Parts + labor, varies by vehicle and location
DTC P0C23 indicates an open circuit condition in the auxiliary transmission fluid pump control module wiring. The auxiliary pump is used in many modern automatic and hybrid transmissions to maintain fluid pressure when the engine is off or during electric-only driving. An open circuit means the cont...
The most common cause of P0C23 (Auxiliary Transmission Fluid Pump Control Module Circuit/Open) is: Broken or disconnected wiring harness to auxiliary pump control module
Typical repair costs for P0C23 range from $150 to $800, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Loss of auxiliary pump function can cause transmission overheating and accelerated wear during stop-start or EV-mode operation. Continued driving may result in transmission damage. Avoid extended low-speed or stop-and-go driving until repaired.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0C23 to identify the root cause.
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Quick Info
Category
Powertrain
System
Transmission / Hybrid Drivetrain
Difficulty
Type
Generic (SAE)
Recommended Tools
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