P0D77

What it means

P0D77 means the A/C compressor control module has seen a voltage from its internal output driver temperature sensor circuit that is higher than expected. This is typically on vehicles with an electrically driven or separately controlled A/C compressor. The module monitors the temperature of its output driver and sets the code when the signal sits above the normal range, which points to a circuit fault, a sensor fault or a fault within the module itself. The exact layout depends on the model and system.

Symptoms

• A/C blowing warm or not cooling
• A/C compressor not running or shutting off intermittently
• Warning light on the dashboard, or an A/C or hybrid system message on some models
• Reduced A/C performance, especially in hot weather
• Other related A/C or compressor module codes stored alongside it

Possible causes

• Fault within the A/C compressor control module, including its internal temperature sensorlikely
• Damaged, corroded or loose wiring or connector at the compressor or modulelikely
• Open circuit or short to voltage in the temperature sensor signal wiring, where the sensor is external to the modulepossible
• Overheating of the compressor module caused by a failing compressor, poor cooling or an overloaded systempossible
• Low or unstable supply voltage or poor earth to the modulepossible
• Outdated module software where the manufacturer has issued a known fixrare

How to diagnose

1. Read all stored and pending codes and record the freeze frame data, noting any other A/C, compressor or high-voltage system codes.
2. Check the A/C system for obvious faults: look at the refrigerant pressure readings, listen for the compressor, and check for any related warnings.
3. Visually inspect the compressor module wiring, connectors and harness for chafing, corrosion, water ingress, heat damage and bent or pushed-back pins.
4. Check the battery condition and the module's supply and earth connections for voltage drop under load.
5. Using live data, check the reported driver temperature against ambient and compressor temperature on a cold car; a reading stuck at maximum suggests an open circuit or a faulty sensor.
6. Test the sensor signal circuit for continuity, short to voltage and short to earth against the wiring diagram for that model, with the module disconnected.
7. Check that the compressor and module are cooling properly and that the A/C system is not overloaded or restricted, following the manufacturer's procedure.
8. Check for software updates or technical bulletins for the model, then clear the code and retest to see whether it returns.

How to fix

• Repair or replace damaged wiring, and clean or replace corroded or damaged connectors.
• Restore a good supply and earth to the module by repairing the voltage drop or loose connections.
• Replace the compressor control module or the compressor assembly if the internal sensor or driver has failed, as per the model's service procedure.
• Correct any cause of overheating, such as a faulty compressor or incorrect refrigerant charge, before replacing parts.
• Update the module software if an outdated calibration is a known cause for the vehicle.

Can I keep driving?

Nearby codes

• P0D76GenericA/C Compressor Control Module Output Driver Temperature Sensor Performance
• P0D78GenericA/C Compressor Control Module Output Driver Temperature Sensor Circuit Low