Powertrain, generic · Hybrid propulsion

P0AF4 Drive Motor Inverter Temperature Sensor B Circuit Low

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

P0AF4 reports a signal of inverter temperature sensor B below the valid range. GM uses an NTC thermistor with a pull-up, so a low voltage reads as an inverter far hotter than possible, usually from a short to ground or an internal sensor fault in the motor B inverter. GM's thresholds: above 170 °C for 2.5 of 3.5 s, Type B, two trips, in the 2016 to 2019 hybrid tables; above 159 °C, Type A, one trip, in another 2019 table; above 130 °C, Type A, on the 2011 Volt; above 125 °C, Type B, on the 2011 and 2013 two-mode trucks. A genuine overheat is reported separately as an over-temperature code such as P0A3D or P0C14. Because the sensor sits inside the inverter, the fix is usually the inverter assembly.

Likely causes

Shorted sensor or circuit inside the power inverter module
Sensor signal shorted to ground in external wiring, where present
Moisture or coolant inside the inverter housing

Symptoms

  • Malfunction indicator lamp and hybrid warning
  • Motor B power strongly limited
  • Reduced hybrid assist and regeneration

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€300–5,000
Time1–6 h

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

Parts involved

drive motor inverter temp sensor bhybrid control modulewiring harness

Related codes

P0AF5P0AF2P0AF3P0AF6P0AEFP0A3D

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