Powertrain, generic · Hybrid propulsion

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

Check engine lightOn

EmissionsRelevant

Drive cycleRequired

Limp modeNo

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.

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

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

Repair estimate

DifficultyMediumWorkshop job

Parts and labour€40–450

Time0.5–2.5 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

hybrid electronics coolant temp sensor awiring harnesshybrid control module

References: gsi.ext.gm.com, gsi.ext.gm.com, gsi.ext.gm.com, gsi.ext.gm.com.