P0D78A/C Compressor Control Module Output Driver Temperature Sensor Circuit Low
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Needs a drive cycle to confirm a fix
- How the car detects it
- 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.
- What you may notice
- Check engine light after two trips
- Air conditioning switched off
- Likely causes
- LikelyShort circuit in the IGBT temperature sensor path
- RareReal overheating of the power stage from high load or poor condenser cooling
- RareFaulty value transmission to the host controller
- Repair
- Workshop only · Usually a job for a workshop.Typical cost: €100 – €2,500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.