Powertrain, generic (extended)

P2C37 Cold Start Engine Coolant Pump Performance

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

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.

Likely causes

Switchable pump stuck engaged or disengaged (clutch, shroud or valve actuator)
Electric coolant pump with failing motor or electronics
Air in the system or low coolant level
Coolant or head temperature sensor reading wrong and misleading the check

Symptoms

  • MIL on
  • Slow warm-up and weak cabin heat, or rising temperature when the pump stays off
  • Overheating warning possible in severe cases

Repair estimate

DifficultyHardWorkshop job
Parts and labour€200–1,200
Time1–4 h

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

Parts involved

engine coolant pumpengine coolant loop

Related codes

P2DE9P2E82P26CBP2B85P050C

References: law.cornell.edu, patents.google.com.