P23C3 is the general electrical fault on the feedback sensor that tells the engine module how far the third coolant bypass valve has turned. On modern thermal management modules this valve is a motor-driven rotary part, so without a valid angle the module loses its closed-loop positioning. No manufacturer documents P23C3 publicly. GM's 2025 engine tables read the same sensor digitally via SENT and only split it into low and high cases (P23C4, P23C5); a fault that fits neither window would fall under this umbrella code. CARB counts such cooling actuators and their sensors among the monitored comprehensive components. The driver may see slow warm-up, a higher or fluctuating temperature gauge and a warning lamp; motor driver faults are P26B7 to P26B9.
Medium severity. Can I keep driving?Watch the temperature gauge. If it climbs or a warning appears, stop the car in a safe place and turn off the engine: overheating can cause serious damage.
Symptoms
- Engine warning lamp
- Engine takes longer to reach operating temperature
- Coolant temperature gauge reads unusually high or unsteady
Most likely causes
- Loose, corroded or coolant-contaminated connector at the valve module
- Damaged signal, 5 V reference or ground wire of the position sensor
- Internal failure of the position sensor built into the valve actuator
- Faulty sensor input or reference supply in the engine control module
What to check, in order
Start with the simplest. You can tick off each step.
Good to know
- Repair difficulty: medium
- It can trigger limp mode.
- It affects emissions.
What each character of P23C3 means
- P: Powertrain: engine and transmission
- 2: Generic code: same on every make
- 3: Ignition and misfires
- C3: Specific fault in that system
Frequently asked questions
Can I keep driving with code P23C3?
Watch the temperature gauge. If it climbs or a warning appears, stop the car in a safe place and turn off the engine: overheating can cause serious damage.
What causes code P23C3?
The most common causes are: loose, corroded or coolant-contaminated connector at the valve module; damaged signal, 5 V reference or ground wire of the position sensor; internal failure of the position sensor built into the valve actuator.
Related codes
- P23C4Engine Coolant Bypass Valve C Position Sensor Circuit Low
- P23C5Engine Coolant Bypass Valve C Position Sensor Circuit High
- P26BBEngine Coolant Bypass Valve C Range/Performance
- P26B7Engine Coolant Bypass Valve C Control Circuit/Open
- P26A4Engine Coolant Bypass Valve A Position Sensor Circuit
- P2AA7Engine Coolant Bypass Valve B Position Sensor Circuit
Sources
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.