P0CAB: Hybrid/EV Battery Temperature Sensor M Circuit High

What does P0CAB mean?

P0CAB is logged when the input of sensor M rises beyond its upper voltage limit. If the thermistor, one of its wires or the plug opens up, the pull-up resistor lifts the input, and the controller reads a temperature far below anything plausible. GM's HPC2 table 18OBDG02 sets it when 8 of 10 readings at 100 ms intervals are colder than −69 °C, as a Type B fault needing over 10.2 V and intact communication. In the 2011 Volt table the limit was −40 °C, a raw count above 4,000, held 1.4 s within 2 s, and a single trip was enough. Mitsubishi treats it as an open circuit of sensor [12] on the Outlander PHEV: above 3.97 V, below about −62 °C, for 2 s. A plug-in may then heat its battery needlessly or start the engine; P0CAA is the low partner.

The code tells you which monitor failed, not which part is broken. Test before replacing parts.

Symptoms

• Battery shown as very cold in mild weather
• Reduced electric power, engine running more on plug-ins

Common causes

• High Open circuit or unplugged connector of sensor M
• Medium Thermistor M open internally
• Low Corroded or spread terminal at the monitoring board

Likelihood is a general estimate across vehicles; your make and model may differ.