Code
P0CE9
Generic
P — Powertrain
Hybrid/EV Electronics Coolant Pump A Control Circuit/Open
AI status
Completed
Completed
100%
Causes
- Open or high-resistance wiring in pump control or ground circuit
- Disconnected, corroded or damaged connector at pump or controller
- Blown fuse or tripped relay supplying pump power
- Failed pump motor (open winding) or internal connector fault
- Faulty controller / driver output (PCM/VCU) or software error
- Poor battery/low-voltage supply to pump (low system voltage)
Symptoms
- DTC P0CE9 stored and/or warning light for hybrid/EV cooling system
- Hybrid/EV power electronics temperature rising or thermal derate
- No audible/visible operation of coolant pump when commanded
- Reduced HVAC or charging performance if electronics overheat
- Intermittent pump operation or faults that clear with connector wiggle
What to check
- Read freeze frame and full trouble code history; attempt to reproduce fault by commanding pump with a scan tool
- Visual inspection of pump, connectors, wiring harness for damage or corrosion
- Check related fuses and relays for continuity and proper seating
- Measure supply voltage at pump power terminal with key ON and while commanding pump
- Measure continuity/resistance of control and ground circuits between pump connector and controller
- Use a scope or oscilloscope to check for PWM or driver signal from the controller while commanding the pump
Signal parameters
- Supply voltage at pump power terminal: ~10–14 V (12 V systems) when commanded
- Control/driver output: switched ground or PWM signal, duty cycle 0–100% depending on demand
- Expected PWM frequency: commonly 50–500 Hz (manufacturer-specific)
- Pump motor coil resistance: typically low (
- Current draw when running: can range from
- Open-circuit: infinite resistance on control or motor winding; no voltage change on command at pump connector
Diagnostic algorithm
- Retrieve freeze frame, note conditions at fault occurrence, and clear codes.
- Attempt to reproduce by commanding Pump A ON with a dealer-level scan tool while monitoring for DTC return.
- Visually inspect pump, harness, and connectors for damage, corrosion, or water intrusion; repair obvious issues.
- Verify low-voltage supply: check fuse(s) and measure battery voltage at pump power pin with pump commanded ON.
- Check ground: measure continuity from pump ground terminal to chassis/negative battery; repair poor ground.
- Check control circuit: with scan tool command active, probe controller output for voltage/PWM with a scope or multimeter (AC/pulse function). No signal indicates open/driver fault or broken wiring.
Likely causes
- Broken or pinched control wire between pump and controller
- Severed ground or poor chassis ground at pump mounting
- Corroded terminal or water ingress at the pump connector
- Blown or loose low-voltage fuse/relay in pump feed
- Pump motor open winding or internal connector failure
- Damaged driver transistor inside control module
Fault status
Status
Control circuit OPEN detected for Hybrid/EV Electronics Coolant Pump A — no control signal or open circuit on pump control/ground path.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
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