P0CBC: Drive Motor A Coolant Temperature Sensor Circuit
What to do
As P0CBC — expect the car to reduce power under sustained load rather than fail outright. Check which of the three cooling circuits this vehicle's motor uses and whether it takes coolant or oil; they have separate reservoirs and the wrong one gets topped up surprisingly often.
What this code means
The sensor measuring the coolant temperature at drive motor A has a circuit fault.
A third cooling circuit, and it is worth keeping the three apart because their codes look alike and their repairs do not. The electronics loop cools the inverter, charger and converter (P0C31, P0CEE). The battery loop cools the pack (P0C42). This one cools the machine itself.
Motors need it more than people expect. Almost all the energy an electric motor wastes turns into heat inside the windings and the rotor, where there is no airflow and nowhere for it to go, and the losses rise sharply with torque. So a motor asked to pull hard — towing, a long climb, repeated hard acceleration — heats up quickly and cools slowly. Many designs spray oil directly through the rotor rather than relying on a jacket, which is why the fluid in this circuit is sometimes not coolant at all.
The consequence of losing the measurement is the same as everywhere in this block: the car derates rather than fails. It quietly reduces the torque it will allow, and the driver reports a car that went flat on a hill and recovered afterwards.
Likely causes
Start here
- Faulty inverter coolant temperature sensor · moderate
- Corroded or loose connector · easy
Less common
- Low inverter coolant level · easy
- Chafed harness between transaxle and inverter · specialist
Symptoms
Components involved
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
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Nothing posted about this yet. Whatever you found is worth writing down — even a dead end saves someone the same afternoon.
What makes one worth reading:
- The car — make, model, year and engine. The same fault behaves differently on each.
- What you measured, not only what you replaced.
- What actually fixed it — or that nothing did, which is worth knowing too.
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