P2C49

Code

Generic P — Powertrain

Coolant Pump D Control Circuit Performance/Stuck Off

Brand: Generic

Type: P — Powertrain

Views: UK: 21 EN: 29 RU: 21

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Page language: EN

Causes

Open or shorted wiring in coolant pump D circuit
Corroded or loose connector at pump or control module
Failed coolant pump (motor seized or open)
Blown fuse or failed relay supplying pump
Failed driver/transistor (MOSFET) inside the control module
Water intrusion/contamination at pump connector

Symptoms

Malfunction Indicator Lamp (MIL) illuminated and DTC stored
Cooling pump D does not run when commanded
Engine runs hotter than normal or overheats under load
Reduced cabin heating or HVAC performance (if pump affects heater circuit)
Possible abnormal coolant temperature readings or limp-home behavior

What to check

Read and record stored DTC(s) and freeze frame data with a scan tool
Check for related codes that point to power/ground or module faults
Visually inspect pump D connector, wiring harness, and mounting for damage or corrosion
Verify fuses and relays for the pump circuit
Backprobe the pump connector and measure supply voltage and ground with key ON and while commanding pump ON
Measure pump motor resistance and check for continuity to ground

Signal parameters

Supply voltage (ignition ON): ~11–14 V at the pump power terminal
Command signal: typically a switched battery feed or PWM from ECM — duty cycle varies 0–100% when commanded
Expected pump current when running: typically 0.5–15 A depending on pump design (measure with appropriate meter)
Pump motor resistance (stator winding): usually low ohms; open circuit or very high resistance indicates a failed motor
Driver output voltage to ground or on/off state when commanded: toggles between near 0 V (drive) and battery voltage (off) or PWM waveform

Diagnostic algorithm

Capture freeze frame and note operating conditions when fault set (engine temp, speed, battery voltage).
Clear codes, then re-run test to confirm repeatability and whether code returns.
Visually inspect wiring, connectors, and pump for damage, corrosion, water ingress, or loose pins. Repair as needed.
Verify fuses and relay(s) for the coolant pump circuit. Replace any blown fuse and re-test.
Using a scan tool, command Coolant Pump D ON while monitoring actual pump status if the tool supports commanded outputs.
Backprobe the pump connector: with pump commanded ON measure supply voltage and the return/driver signal. Record voltages and waveform (use scope if available).
If no supply voltage is present, trace back to fuse/relay/power feed and repair open circuit. If supply present but driver output is inactive, suspect ECM/PCM driver fault.
Measure motor resistance and inspect for short to ground/short to battery. If motor shows open/high resistance or binds, remove pump and perform a bench 12 V test to confirm operation.
If pump runs on bench and wiring/connector are good, inspect ECM/PCM driver output for intermittent short or open. Check for blown driver components or internal faults.
Repair or replace failed component(s): wiring, connector, pump, fuse/relay, or control module as indicated by tests.
After repairs, clear codes and perform functional test and road test to confirm the fault does not return.
Safety: use proper PPE when working around coolant system and electrical circuits; relieve system pressure and allow engine to cool before accessing pump area.