P0EF4: Drive Motor C Temperature Sensor Circuit High

P0EF4 reports a drive motor C temperature signal above the plausible window. For an NTC sensor on a pull-up this equals an impossibly cold winding, the picture produced by an open sensor, a broken wire, an unplugged connector or a short to the reference voltage. No manufacturer documents P0EF4 publicly. GM's ELR motor controller treats the same situation for motor B as P0A33 once the value reads below −41 °C, near 5 V, while Ford flags the coil sensor of its 2019 hybrids once the voltage exceeds 4.8 V for 32 ms. A sensor that claims far too low a temperature would hide real overheating, so the controller switches to a substitute value and limits the output of motor C. Check the connector at the motor first; the low-side sibling is P0EF3.

Symptoms

• Reduced power of motor C
• Motor temperature stuck at the lowest value in the live data
• Warning lamp on

Most likely causes

• Sensor connector unplugged, loose or with pushed-back pin
• Broken signal or ground wire of the sensor
• Thermistor open internally
• Signal wire shorted to the 5 V reference

What to check, in order

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

1. Read the codes with a hybrid-compatible scanner and write down the freeze frame data
2. Check the sensor's ground and make sure the signal wire is not receiving voltage from another circuit.
3. Make sure the battery cooling air intake is clean
4. Check the 12 V auxiliary battery, which can also trigger warnings
5. Leave any high-voltage measurements to a specialized repair shop

Good to know

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

What each character of P0EF4 means

• P: Powertrain: engine and transmission
• 0: Generic code: same on every make
• E: Subsystem depends on the code range
• F4: Specific fault in that system

Frequently asked questions

Can I keep driving with code P0EF4?

If the car still runs, drive as little as possible and go to a specialized repair shop. Do not touch the orange cables: they carry high voltage.

What causes code P0EF4?

The most common causes are: sensor connector unplugged, loose or with pushed-back pin; broken signal or ground wire of the sensor; thermistor open internally.

Related codes

• P0EF3Drive Motor C Temperature Sensor Circuit Low
• P0EF1Drive Motor C Temperature Sensor Circuit
• P0EF2Drive Motor C Temperature Sensor Range/Performance
• P0EF5Drive Motor C Temperature Sensor Circuit Intermittent/Erratic
• P0A33Drive Motor B Temperature Sensor Circuit High
• P0A2DDrive Motor A Temperature Sensor A Circuit High

Sources

• gsi.ext.gm.com: 16OBDG01 Hybrid Diagnostics
• fordservicecontent.com: OBDSM1901 HEV
• law.cornell.edu: 13 CCR 1968.2

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.