P0C73
Motor Electronics Coolant Pump A Control Performance.
- Generic
- Powertrain
- Generic code
- High severity
How this code is built
- P
- SystemPowertrain
- 0
- Defined bySAE, the same on every car
- C
- AreaHybrid propulsion
- 73
- FaultThe specific fault in that area
What it means
P0C73 is the generic code for a performance fault in the control of motor electronics coolant pump A, which circulates coolant through the power electronics and drive motor cooling circuit on hybrid and electric vehicles. The control unit commanded the pump and found that its actual behaviour, such as speed, feedback or resulting coolant temperatures, did not match what was requested. Exact set conditions and which circuit pump A serves depend on the manufacturer and model.
Symptoms
- Warning light on the dashboard, often a hybrid or EV system or powertrain fault message
- Reduced power or limp mode to protect the inverter and motor
- Power electronics or motor temperature warnings
- Cooling pump noise, whining, or no pump noise at all when it should be running
- Reduced charging rate or limited regenerative braking on some models
- Vehicle refusing to enter ready mode in severe cases
Possible causes
- Faulty electric coolant pump (worn motor, seized or weak impeller, internal electronics failure)likely
- Low coolant level or air trapped in the power electronics cooling circuit, reducing pump flow or feedbacklikely
- Wiring or connector fault in the pump power, ground or control signal circuit (corrosion, chafing, loose pin)possible
- Blocked or restricted coolant hose, radiator or cooling passage reducing flowpossible
- Low or unstable supply voltage to the pump, such as from a weak 12 V battery or poor earthpossible
- Fault in the controlling unit or driver circuit for the pumprare
- Outdated control unit software where the manufacturer has a known issue with pump controlrare
How to diagnose
- Read all stored codes and freeze frame data, noting any coolant, inverter or motor temperature codes and the conditions when the fault set
- Check the coolant level and condition in the correct reservoir for the power electronics circuit, following the manufacturer's guidance for the model
- Inspect the pump wiring, connectors and fuses or relays for damage, corrosion, water ingress or poor fit
- Listen for pump operation with the system awake, and use live data to compare commanded and actual pump speed or duty
- Check the 12 V battery condition and the supply voltage and earth at the pump connector under load
- Check for flow restrictions: kinked or collapsed hoses, a blocked radiator, or air locks, and compare temperatures across the circuit
- Perform any manufacturer-specified pump activation test and check for applicable software updates or service bulletins for the model
How to fix
- Top up or correct the coolant with the specified type and bleed the circuit using the manufacturer's procedure
- Repair or replace damaged wiring, connectors, fuses or relays in the pump circuit
- Replace the coolant pump if it fails the activation test or shows incorrect speed feedback
- Clear restrictions by replacing blocked or collapsed hoses or flushing and refilling the circuit as specified
- Replace or charge the 12 V battery and correct any poor earth connections
- Update the control unit software only if a known fault with pump control applies to the vehicle
Can I keep driving?
Limit driving and avoid it where possible, as inadequate cooling can overheat and damage the inverter or motor, which are costly components. If the car must be moved, drive only a short distance gently, and stop if temperature warnings appear or power drops.
Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.