P0CEF: Hybrid/EV Electronics Coolant Temperature Sensor A Circuit Range/Performance

The sensor stays electrically within range but reports a temperature that does not fit its surroundings. GM uses two kinds of comparison. In the 2011 Volt and the ELR it is checked against the high-voltage charger temperature with the pump running at 30 % or more for over 60 or 300 s; the limit is 38 to 40 °C (2011) or 35 °C (ELR). From the 2016 Volt on the test runs once after a long rest (propulsion off over 18,000 or 21,600 s, pump and A/C off for 3,600 s) and compares with outside air, transmission fluid and A/C high-side temperature; limits are 27/27/28 °C, 21/35 °C in 16OBDG02. GM uses 32 of 40 samples or 8 s in 10 s, Type B, two trips. Hard circuit faults are P0CF0/P0CF1, noise P0CF2. A wrong reading misleads the cooling and power limits.

Symptoms

• Malfunction indicator lamp on, often without noticeable drivability change
• Electronics coolant pump runs at odd times or longer than usual
• Occasional power or charging limitation

Most likely causes

• Sensor element drifted and reads offset from the real coolant temperature
• Added resistance from corroded terminals shifting the signal
• Genuine temperature gap from poor flow or air in the electronics loop
• Comparison sensor (charger, outside air or transmission fluid) reading wrong without its own code

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. Compare the reading with other engine data while varying the engine speed.
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: medium
• It affects emissions.

What each character of P0CEF means

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

Frequently asked questions

Can I keep driving with code P0CEF?

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 P0CEF?

The most common causes are: sensor element drifted and reads offset from the real coolant temperature; added resistance from corroded terminals shifting the signal; genuine temperature gap from poor flow or air in the electronics loop.

Related codes

• P0CEEHybrid/EV Electronics Coolant Temperature Sensor A Circuit
• P0CF0Hybrid/EV Electronics Coolant Temperature Sensor A Circuit Low
• P0CF1Hybrid/EV Electronics Coolant Temperature Sensor A Circuit High
• P0CF2Hybrid/EV Electronics Coolant Temperature Sensor A Circuit Intermittent/Erratic
• P0CEAHybrid/EV Electronics Coolant Pump A Performance
• P0071Ambient Air Temperature Sensor Circuit A Range/Performance
• P0711Transmission Fluid Temperature Sensor A Circuit Range/Performance
• P2B21Hybrid/EV Electronics Coolant Temperature Sensor B Circuit Range/Performance

Sources

• gsi.ext.gm.com: 11OBDG01 HYBRID Diagnostics
• gsi.ext.gm.com: 16OBDG01 Hybrid Diagnostics
• gsi.ext.gm.com: 16OBDG02 Hybrid Diagnostics
• gsi.ext.gm.com: 19OBDG01 Hybrid Diagnostics

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.