P2C37Cold Start Engine Coolant Pump Performance
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Needs a drive cycle to confirm a fix
- How the car detects it
- Engines with a switchable or electric main coolant pump often keep the coolant still, or nearly so, right after a cold start so the cylinder head and catalyst warm up sooner. P2C37 reports that the pump did not behave as commanded during this cold-start phase, for example running when it should rest or failing to start when flow is requested. California rules require separate codes for faults detected during a cold-start strategy and ask makers of electric water pumps to submit a monitoring plan of their own. No manufacturer documents P2C37 publicly. An Audi patent shows one way to judge such a pump: once it is switched back on, the measured head temperature is checked against a model value derived from coolant temperature. Related are P2DE9/P2E82 (cold-start under- and overspeed) and P26CB.
- What you may notice
- MIL on
- Slow warm-up and weak cabin heat, or rising temperature when the pump stays off
- Overheating warning possible in severe cases
- Likely causes
- LikelySwitchable pump stuck engaged or disengaged (clutch, shroud or valve actuator)
- PossibleElectric coolant pump with failing motor or electronics
- PossibleAir in the system or low coolant level
- RareCoolant or head temperature sensor reading wrong and misleading the check
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Hard · Usually a job for a workshop.Typical cost: €200 – €1,200
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.