P2C37

Code

Generic P — Powertrain

Cold Start Engine Coolant Pump Performance

Brand: Generic

Type: P — Powertrain

Views: UK: 23 EN: 32 RU: 22

AI status

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Page language: EN

Causes

Faulty cold-start/auxiliary coolant pump (mechanical or electrical failure)
Open/short/intermittent wiring or poor connector connection to pump
Failed pump relay or fuse
Low coolant level or air trapped in cooling system preventing flow
Blocked or collapsed coolant hose or cooling passage restricting flow
Corroded or poor ground(s)

Symptoms

MIL/Check Engine lamp illuminated
Extended warm-up time or slow engine warm-up on cold start
Reduced cabin heater output during warm-up
Unusual whining/grinding noise from pump area
Coolant temperature behavior inconsistent with ambient (slow to rise)
Possible increased cold-start emissions or rough idle until warm

What to check

Pull freeze frame and readiness data with a scan tool; note coolant temp at fault and pump command status
Visual inspection of pump, wiring harness, connectors, fuse and relay for damage or corrosion
Verify coolant level and check for air in system; pressure test cooling system for leaks
Command pump ON/OFF with a capable scan tool and observe operation (noise, flow, current)
Back-probe pump power and ground while commanded; measure voltage and duty cycle
Measure pump current draw with a clamp meter and compare to spec (or known-good pump)

Signal parameters

PCM command (ON/OFF or duty cycle %) to coolant pump
Pump supply voltage (V) while commanded ON
Pump control frequency or PWM duty (%) if applicable
Pump current draw (A) or resistance (Ω) of motor
Engine coolant temperature at time of event (°C/°F)
Freeze frame data: vehicle speed, ignition status, battery voltage, ambient temp

Diagnostic algorithm

Retrieve P2C37 and any additional codes; record freeze frame and live data (ECT, battery voltage).
Visually inspect pump, wiring, connectors, ground points, fuse and relay. Repair obvious issues.
Verify coolant level and inspect for trapped air; top up and bleed system if low/air present. Pressure test for leaks if needed.
With scan tool, command the coolant pump on and observe: listen for operation, watch for expected change in current/voltage and coolant temperature response. Note if pump does not run or runs weakly.
Measure voltage at the pump positive terminal during command (should be near battery voltage minus expected drop); check ground integrity. If no proper voltage, troubleshoot upstream (relay, fuse, PCM output).
Measure pump current draw; compare to specification or to a known-good pump. High current suggests mechanical bind/short; no/low current suggests open circuit or failed motor. Bench-test pump off-vehicle if unsure.
Inspect and clear any restrictions: hoses, check valves, or passages that would prevent flow. Replace components as required.
If electrical circuits check good and pump functions on bench but PCM command is abnormal, inspect PCM outputs, grounds, and software. Check for TSBs/PCM updates before replacing PCM.
Replace faulty component(s) (pump, relay, wiring, sensor) as verified. After repair, clear codes and perform required relearn/drive cycle to confirm proper operation and that P2C37 does not return.

Likely causes

Pump motor failure or worn brushes (no spin or weak spin)
Open/short in pump power or ground circuit
Failed relay or blown fuse in pump supply circuit
Coolant low or air lock preventing expected flow
Connector corrosion or pin damage causing intermittent supply

Fault status

⚠️ Status

P2C37 — Cold Start Engine Coolant Pump Performance: PCM detected coolant pump did not perform within expected parameters during cold-start. Inspect pump operation, electrical supply, coolant level/flow, and related sensors.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0 - 3.0 hours