Powertrain, generic · Hybrid propulsion

P0CB4 Hybrid/EV Battery Temperature Sensor O Circuit Low

Check engine lightOn

EmissionsRelevant

Drive cycleRequired

Limp modePossible

P0CB4 reports a signal voltage of sensor O below its lower limit. The sensor is an NTC thermistor biased by a resistor on the measuring board, so a short to ground or a shorted element looks like extreme heat. GM's HPC2 table 18OBDG02 fails the test when the converted value is above 160 °C in 8 of 10 readings at 100 ms, Type B, with more than 10.2 V supply; the 2011 Volt table used 87.5 °C, a raw count below 680, for 1.4 s within a 2 s window over two trips. In GM's 2019 table the pack over-temperature monitor P0A7E is suspended while such short codes are active, because a false hot reading would otherwise trigger it. Mitsubishi calls P0CB4 a short of module sensor [14] on the Outlander PHEV: under 0.12 V, roughly above 125 °C, for 2 s.

Likely causes

Signal lead of sensor O shorted to ground in the pack

Thermistor O shorted internally

Input stage of the cell monitoring unit defective

Symptoms

Live data showing an implausibly hot module
Strongly reduced battery power with warning lamp
Battery cooling running without obvious need

Repair estimate

DifficultyShop_onlyWorkshop job

Parts and labour€150–3,000

Time1–5 h

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

Parts involved

hv battery temp sensor owiring harnessbms

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