Powertrain, generic · Hybrid propulsion

P0D78 A/C Compressor Control Module Output Driver Temperature Sensor Circuit Low

Check engine lightOn
EmissionsNot relevant
Drive cycleRequired
Limp modeNo

P0D78 is set when the output driver (IGBT) temperature sensor of the electric A/C compressor signals low, which for an NTC sensor means an implausibly hot value. GM uses 274 °C or more in the 2011–2015 Volt and the 2016 ELR, and above 150 °C in the 2016–2019 Volt; detection takes 30 of 60 samples at 50 ms, 40 of 50 at 100 ms or 4 of 5 s, Type B with MIL after two trips. Temperatures like these are beyond what the power stage survives, so a shorted sensor is more likely than real heat, although a seized compressor or a failed condenser fan can drive the IGBTs hot. Expect the A/C to switch off. The cold-side counterpart is P0D77, plausibility P0D76.

Likely causes

Short circuit in the IGBT temperature sensor path
Real overheating of the power stage from high load or poor condenser cooling
Faulty value transmission to the host controller

Symptoms

  • Check engine light after two trips
  • Air conditioning switched off

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

ac compressor cm output driver temp sensorac compressor module

Related codes

P0D77P0D76P0D75P0D79P0D73

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