P0D79: A/C Compressor Control Module Output Driver Temperature Sensor Circuit Intermittent/Erratic

P0D79 marks an erratic signal from the output driver temperature sensor, the sensor that guards the compressor's power transistors: values flicker or drop out briefly instead of staying wrong. No manufacturer publishes set criteria. GM's 2019 Volt table lists P0D79 next to P0D77 and P0D78 as an IGBT-sensor circuit fault that suspends the plausibility checks, which shows the code is in use, but without thresholds. A Hyundai patent on temperature sensors for power switches names loose connectors, electrical noise, board defects and cold solder joints as typical origins of such unstable readings. Because the compressor can no longer trust its overheat protection, it may cut out repeatedly. CARB requires thermal-management inputs to be checked for circuit faults.

Symptoms

• Air conditioning cuts out repeatedly
• Code appears sporadically

Most likely causes

• Cold or cracked solder joint at the IGBT sensor
• Loose low-voltage connector or ground at the compressor
• Switching noise from the inverter coupling into the sensor signal

What to check, in order

Start with the simplest. You can tick off each step.

1. Check the battery and grounds
2. Gently move the wiring with the engine running and watch whether the reading changes.
3. Clear the code and see if it returns
4. If it is a reference voltage code, disconnect sensors one at a time and see if the voltage recovers
5. Check whether a software update is available
6. Do not replace the control module without a full diagnosis

What each character of P0D79 means

• P: Powertrain: engine and transmission
• 0: Generic code: same on every make
• D: Subsystem depends on the code range
• 79: Specific fault in that system

Frequently asked questions

Can I keep driving with code P0D79?

It depends on the symptoms. If the car is running normally you can go to a repair shop; if it goes into limp mode, drive as little as possible.

What causes code P0D79?

The most common causes are: cold or cracked solder joint at the IGBT sensor; loose low-voltage connector or ground at the compressor; switching noise from the inverter coupling into the sensor signal.

Related codes

• P0D75A/C Compressor Control Module Output Driver Temperature Sensor Circuit
• P0D76A/C Compressor Control Module Output Driver Temperature Sensor Performance
• P0D77A/C Compressor Control Module Output Driver Temperature Sensor Circuit High
• P0D78A/C Compressor Control Module Output Driver Temperature Sensor Circuit Low
• P0D74A/C Compressor Control Module Internal Temperature Sensor A Circuit Intermittent/Erratic

Sources

• law.cornell.edu: 13 CCR 1968.2
• gsi.ext.gm.com: 19OBDG01 Hybrid Diagnostics
• patents.google.com: en

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.