Powertrain, generic · Hybrid propulsion

P0C9B Hybrid/EV Battery Temperature Sensor L Circuit Intermittent/Erratic

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

P0C9B covers a sensor L signal that jitters. GM's tables 18OBDG02 and 19OBDG02 integrate the absolute sample-to-sample changes over ten readings spaced 100 ms apart; when the integral exceeds 10, that window fails, and 4 failures within 5 windows store the code, classed Type B. Supply must exceed 10.2 V and communication with the battery interface module must be present. Because the value may never leave its valid band, P0C99 and P0C9A can stay silent. Mitsubishi does not use this code. A fretting pin, a cracked conductor or a loose board ground are typical, and the fault may vanish between drives, so freeze-frame data and a wiggle test help to find it.

Likely causes

Fretting pin in the sensor L connector
Cracked conductor in the sensor L lead
Loose ground on the cell monitoring board

Symptoms

  • Warning lamp that may switch off again by itself
  • Erratic sensor L value in live data

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€100–2,500
Time1–5 h

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

Parts involved

hv battery temp sensor lwiring harnessbms

Related codes

P0C97P0C98P0C99P0C9AP0C96P0CAC

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