P0C73: Motor Electronics Coolant Pump A Control Performance

P0C73 reports that coolant pump A of the motor electronics, the loop that cools the inverter and often the drive motor, does not run the way the controller commands. Kia's bulletins for Niro and Carnival hybrids use exactly this name. The 2018 Outlander PHEV sets it when, with at least 30 % pump command for over 2 s, pump speed stays between 100 and 1,000 rpm or exceeds 5,300 rpm for 0.5 s; Mitsubishi lists air in the loop, wrong coolant level or mix and frozen coolant first. Toyota tied P0C73 on the 2014-2016 Highlander Hybrid to water corroding the inverter pump connector, Kia to water entering the pump can, Mercedes (M264) to trapped air. Battery pack pump faults use P0C47-P0C4D. Power is reduced to protect the inverter.

Symptoms

• Malfunction indicator lamp or hybrid warning lamp
• Coolant warning in the instrument cluster
• Reduced electric drive power at high load

Most likely causes

• Air trapped in the inverter cooling loop, often after coolant service
• Water ingress and corrosion at the pump connector or inside the pump housing
• Low coolant level, wrong mixture or frozen coolant
• Electric pump worn or seized
• Control-unit software with faulty judgement logic

What to check, in order

Start with the simplest. You can tick off each step.

1. With the engine cold, check the coolant level; never do this when the system is hot
2. Compare the reading with other engine data while varying the engine speed.
3. Check the actual temperature in live data
4. Make sure the fan comes on when it should
5. Check the thermostat and connector
6. Measure the sensor and replace it if its readings do not make sense

Good to know

• Repair difficulty: medium
• It can trigger limp mode.
• It affects emissions.

What each character of P0C73 means

• P: Powertrain: engine and transmission
• 0: Generic code: same on every make
• C: Subsystem depends on the code range
• 73: Specific fault in that system

Frequently asked questions

Can I keep driving with code P0C73?

Watch the temperature gauge. If it climbs or a warning appears, stop the car in a safe place and turn off the engine: overheating can cause serious damage.

What causes code P0C73?

The most common causes are: air trapped in the inverter cooling loop, often after coolant service; water ingress and corrosion at the pump connector or inside the pump housing; low coolant level, wrong mixture or frozen coolant.

Related codes

• P0C74Motor Electronics Coolant Pump B Control Performance
• P2BD7Motor Electronics Coolant Pump C Control Performance
• P2600Coolant Pump A Control Circuit/Open
• P2601Coolant Pump A Control Circuit Performance/Stuck Off
• P0C4AHybrid/EV Battery Pack Coolant Pump A Control Performance

Sources

• static.nhtsa.gov: MC 10187725 0001
• mitsubishitechinfo.com: M154920700016600USA
• static.nhtsa.gov: MC 10141502 9999
• static.nhtsa.gov: MC 11005314 0001

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.