P0C23: Electric/Auxiliary Transmission Fluid Pump Control Module Circuit/Open

P0C23 is set by the controlling module, usually the PCM, TCM or hybrid controller, when the circuit to the auxiliary pump control module is open. J2012 does not name the line further; in practice it is the command or enable wire. Ford's 2016 F-150 2.7L bulletin shows such a command: the PCM drives the pump with a duty cycle that a scan tool can vary from 20 to 90 percent. GM's ELR pump controller only runs its phase tests while a wake-up signal is on. No manufacturer publicly documents P0C23 itself. With the line open the pump gets no command and stays off, so auto-stop is disabled and pressure support is missing. P0C24 and P0C25 are the low and high variants, P0C2B to P0C2E the feedback line in the other direction.

Symptoms

• Start-stop no longer works
• MIL or transmission warning
• Harsh engagement after an engine stop

Most likely causes

• Open command or enable wire between controller and pump module
• Pushed-out or corroded terminal at the pump module or controller connector
• Input stage of the pump control module faulty

What to check, in order

Start with the simplest. You can tick off each step.

1. Check the battery and grounds
2. Check the continuity of the wire between the component and the control module.
3. Clear the code and see if it returns
4. If it is a reference voltage code, disconnect sensors one at a time and see if the voltage recovers
5. Check whether a software update is available
6. Do not replace the control module without a full diagnosis

Good to know

• Repair difficulty: medium
• It can trigger limp mode.
• It affects emissions.

What each character of P0C23 means

• P: Powertrain: engine and transmission
• 0: Generic code: same on every make
• C: Subsystem depends on the code range
• 23: Specific fault in that system

Frequently asked questions

Can I keep driving with code P0C23?

It depends on the symptoms. If the car is running normally you can go to a repair shop; if it goes into limp mode, drive as little as possible.

What causes code P0C23?

The most common causes are: open command or enable wire between controller and pump module; pushed-out or corroded terminal at the pump module or controller connector; input stage of the pump control module faulty.

Related codes

• P0C24Electric/Auxiliary Transmission Fluid Pump Control Module Circuit Low
• P0C25Electric/Auxiliary Transmission Fluid Pump Control Module Circuit High
• P0B0DElectric/Auxiliary Transmission Fluid Pump Motor Control Module
• P0C2BElectric/Auxiliary Transmission Fluid Pump Control Module Feedback Signal
• P2796Electric/Auxiliary Transmission Fluid Pump A Control Circuit/Open
• U0287Lost Communication With Transmission Fluid Pump Module A

Sources

• law.cornell.edu: 13 CCR 1968.2
• static.nhtsa.gov: MC 10108996 9999
• gsi.ext.gm.com: 16OBDG01 Hybrid Diagnostics

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.