P23C5 code meaning
Engine Coolant Bypass Valve C Position Sensor Circuit High
Powertrain system Generic code P23xx codes Check engine light
What P23C5 means
With P23C5 the position feedback of coolant bypass valve C sits at the top end of its digital range, a reading GM explains as the signal line touching a voltage source. In GM's 2025 summaries for the 3.0L Duramax (25OBDG04B) and a gasoline engine family (25OBDG03B) the limit is identical: a SENT value above 4,050 counts present for 4 seconds within 5 seconds, checked only when the SENT link reports no error and the engine is not cranking. GM rates it Type B, two trips to the lamp. A high reading can also come from a broken ground at the sensor. Until it is fixed the module cannot trust the valve angle, so coolant routing may be wrong. Low readings are P23C4, general circuit faults P23C3.
P23C5 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyMedium
- Typical labor0.5 to 3 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P23C5
- Engine warning lamp on the second faulty trip
- Live data shows bypass valve C near full scale regardless of command
- Heater output or engine temperature behaves unusually
Common causes of P23C5
- Most likelyPosition signal wire shorted to a supply or reference wire
- PossibleOpen ground wire of the position sensor
- PossiblePosition sensor in the valve actuator reporting a stuck maximum value
- Less likelyBent or spread terminals in the valve connector
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Coolant bypass valve c position sensor
What each part of P23C5 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 2 | Generic code (second SAE range): it means the same on every make. |
| 3 | Area: ignition system or misfire. |
| C5 | The exact fault in that area. |
What to do next
- Note P23C5 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P23C5
What does P23C5 mean?
P23C5 means "Engine Coolant Bypass Valve C Position Sensor Circuit High". With P23C5 the position feedback of coolant bypass valve C sits at the top end of its digital range, a reading GM explains as the signal line touching a voltage source. It is a generic code, so it means the same on every make.
Is it safe to drive with P23C5?
Drive gently and only to a workshop. With P23C5 the car can go into limp mode (reduced power) to protect itself.
Will P23C5 fail an emissions test?
Yes, it can. P23C5 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P23C5 to fix?
Difficulty: medium. A typical repair takes 0.5 to 3 hours of work. This is a job for a workshop.
Will P23C5 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.