Open or high-resistance fault in the sensor signal wire, such as a broken conductor or corroded terminal; Failed coolant temperature sensor that has drifted out of specification or developed an internal open circuit; Poor connection at the sensor connector or at the controller harness, including backed-out pins or water intrusion; High resistance in the sensor ground circuit, which raises the voltage seen on the signal line; Faulty powertrain control module or hybrid control module, though this is the least likely cause; Aftermarket accessories or wiring repairs that have disturbed the sensor circuit

DTC codes / P0Cxx · Hybrid propulsion / P0CBF

P0CBFDrive Motor A Coolant Temperature Sensor Circuit High

Q: What does code P0CBF mean?

Drive Motor A Coolant Temperature Sensor Circuit High. P0CBF indicates that the powertrain control module has detected an abnormally high voltage on the signal circuit of the coolant temperature sensor for drive motor A, which is the main traction motor in a hybrid or electric vehicle. The sensor is a thermistor whose resistance drops as coolant temperature rises, so a high signal voltage tells the controller that the motor coolant is colder than it actually is or that the circuit is open.

P0CBF indicates that the powertrain control module has detected an abnormally high voltage on the signal circuit of the coolant temperature sensor for drive motor A, which is the main traction motor in a hybrid or electric vehicle. The sensor is a thermistor whose resistance drops as coolant temperature rises, so a high signal voltage tells the controller that the motor coolant is colder than it actually is or that the circuit is open.

SystemPowertrain

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyIntermediate

AreaHybrid propulsion

Symptoms you may notice

Illumination of the check engine light or service vehicle soon message, often with no other noticeable symptoms
Reduced power or limp-home mode as the controller limits motor output to protect against perceived overheating
Inaccurate or stuck coolant temperature reading on the instrument cluster or scan tool data stream
Possible activation of the motor cooling fan at full speed or failure of the fan to turn on when needed
In some vehicles, the engine may start or stop unexpectedly as the hybrid control system compensates for the faulty reading

Common causes, most likely first

Open or high-resistance fault in the sensor signal wire, such as a broken conductor or corroded terminal
Failed coolant temperature sensor that has drifted out of specification or developed an internal open circuit
Poor connection at the sensor connector or at the controller harness, including backed-out pins or water intrusion
High resistance in the sensor ground circuit, which raises the voltage seen on the signal line
Faulty powertrain control module or hybrid control module, though this is the least likely cause
Aftermarket accessories or wiring repairs that have disturbed the sensor circuit

How to diagnose and fix it

Connect a scan tool and record the freeze-frame data and coolant temperature reading to confirm the fault is present and not intermittent
Visually inspect the sensor, connector, and harness for damage, corrosion, or loose pins, and repair any obvious defects
Measure the sensor resistance with a multimeter and compare it to the manufacturer's temperature-resistance chart to verify sensor operation
Backprobe the signal circuit at the controller and check for an open or high-resistance condition while wiggling the harness
Check the sensor ground circuit for excessive resistance using a voltage drop test under load
If the circuit and sensor test good, substitute a known-good sensor or simulate the signal with a resistor box to confirm the controller responds correctly
Replace the faulty sensor or repair the wiring as needed, clear the codes, and verify the coolant temperature reading agrees with actual engine or motor temperature

High voltage does not always mean a bad sensor

A high signal voltage is most often caused by an open circuit rather than a shorted sensor, so a broken wire or corroded connector is a more common finding than a failed thermistor.
The motor coolant temperature sensor is sometimes shared with the inverter cooling loop, and a fault in that shared circuit can set this code even when the motor itself is not overheating.
Technicians who replace the sensor without checking the ground circuit often see the code return because a high-resistance ground raises the signal voltage just like an open sensor would.
In some hybrid systems, the controller defaults to a fixed coolant temperature when the signal is lost, which can mask the fault and prevent the cooling fan from operating correctly.
A intermittent fault can be caused by harness chafing near the motor mount or through a bulkhead grommet, so a wiggle test while watching live data is essential before condemning any part.

Can I keep driving with P0CBF?

You can usually drive the vehicle short distances at reduced power, but avoid sustained high-speed driving or heavy loads because the controller may not be able to accurately protect the motor from overheating. If the vehicle enters limp-home mode or the coolant temperature gauge behaves erratically, have it diagnosed promptly.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.