Powertrain, generic (extended)

P23C3 Engine Coolant Bypass Valve C Position Sensor Circuit

Check engine lightOn

EmissionsRelevant

Drive cycleNot required

Limp modePossible

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.

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

Symptoms

Engine warning lamp
Engine takes longer to reach operating temperature
Coolant temperature gauge reads unusually high or unsteady

Repair estimate

DifficultyMediumWorkshop job

Parts and labour€60–900

Time0.5–3 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

coolant bypass valve c position sensor

Related codes

P23C4 P23C5 P26BB P26B7 P26A4 P2AA7

References: gsi.ext.gm.com, law.cornell.edu.