What it means
The motor electronics coolant pump A control circuit reports a control circuit/open condition. Power electronics cooling cannot be commanded reliably.
At a glance
- Usually lights the check-engine light
- The engine or gearbox may go into limp mode
How it works
Motor electronics coolant pump A circulates coolant through the inverter and other hybrid power electronics. P0A05 sets when the pump A control circuit is open or cannot complete the commanded circuit, so the module cannot reliably command that pump.
Common causes
Most likely first.
- Open in pump control wire
- Open pump motor
- Pin pushed back out of connector body
Symptoms
- Hybrid system or check-engine warning light on
- Possible reduced hybrid power
- Cooling fan may run more often
How to diagnose it
- Use a hybrid-capable scan tool to record freeze-frame data and check for related pump or inverter temperature codes before clearing anything.
- Inspect pump A's electrical connector for a loose plug, damaged housing, corrosion, or a terminal pushed back into the connector body.
- Check the pump A control wiring for breaks, chafing, or an open between the pump and its control module.
- With the vehicle made safe under the manufacturer's high-voltage procedures, test the pump motor winding and circuit continuity against the manufacturer's specification.
- If the circuit is intact, use the approved scan-tool command and procedure to verify whether pump A operates and coolant circulates.
Common fixes
- Reseat the pump A connector and secure any displaced terminal.
- Repair an open or damaged pump A control wire.
- Replace pump A if its motor circuit is open or it fails the specified operation test.
- Repair a control-module connection if testing confirms the open is outside the pump and harness.
Can I keep driving?
Avoid driving except to move the vehicle to a safe location, because pump A may not circulate coolant through the hybrid power electronics and reduced-power mode may occur. Stop if a hybrid or temperature warning appears; overheating can quickly damage the inverter or motor electronics.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.