Easy one-page printout for the garage or repair shop
This summary uses the existing diagnostic information shown in full below.
The car's computer thinks that a sensor measuring the temperature of the heat pump is showing a number that's too high. It's like a thermometer showing it's too hot when it shouldn't be.
This code indicates that the temperature reading from the Heat Pump Temperature Sensor 'C' is higher than the expected range.
The P1D79 code is triggered when the Powertrain Control Module (PCM) detects a temperature reading from the Heat Pump Temperature Sensor 'C' that is above the normal operating range. This sensor is responsible for monitoring the temperature of the heat pump system, which is part of the vehicle's climate control system.
• Check Engine Light is on
• Climate control system not functioning properly
• Unusual temperature readings
• Faulty Heat Pump Temperature Sensor 'C'
• Wiring issues or poor connections
• Malfunctioning heat pump system
OBD-II: On-Board Diagnostics, a standardized system for vehicle diagnostics.
PCM: Powertrain Control Module, the computer that controls engine and transmission functions.
• Use an OBD-II scanner to confirm the code.
• Inspect the wiring and connections to the sensor.
• Test the sensor with a multimeter to check for proper operation.
• Replace the Heat Pump Temperature Sensor 'C'.
• Repair or replace damaged wiring or connectors.
• Inspect and repair the heat pump system if necessary.
• OBD-II scanner
• Multimeter
• Basic hand tools
$100 - $300
Moderate
• Honda Accord Hybrid
• Toyota Prius
• Chevrolet Volt
• Regularly inspect and maintain the vehicle's climate control system.
• Ensure all sensors are functioning correctly.
• Check for any wiring damage periodically.
Sensor Issue
• Do not ignore the Check Engine Light.
• Get the vehicle inspected by a professional if unsure.
• Avoid using the climate control system until the issue is resolved.
Check with your vehicle manufacturer for warranty coverage on emissions-related components.
This code has been associated with hybrid and electric vehicles due to their advanced climate control systems.
Moderate – Addressing this issue soon can prevent further complications.
Driving with a malfunctioning climate control system can lead to comfort issues and may affect visibility if defrost functions are impaired.
• Vehicle at operating temperature
• Climate control system activated
The Heat Pump Temperature Sensor 'C' is typically located near the heat pump unit, which is part of the vehicle's HVAC system.
Q: Can I drive with a P1D79 code?
A: It's possible, but not recommended as it may affect your vehicle's climate control system.
Q: How do I reset the P1D79 code?
A: After fixing the issue, you can reset the code with an OBD-II scanner.
High-End · Full-system diagnostics
A full-system bidirectional platform aimed at advanced DIY users and professional diagnostic workflows.
Network faults often require full-system access instead of a generic code reader alone.
View on Amazon
Universal · Digital multimeter
A solid entry-level multimeter for voltage, continuity, resistance, and basic electrical troubleshooting.
Helpful for checking voltage drops, grounds, and basic circuit health when modules are not communicating.
View on Amazon
Universal · Wire connectors and repair kit
Useful when diagnosis points toward damaged wiring, corroded terminals, or connector repairs.
Useful if diagnosis points toward damaged connectors, wiring, or terminal repairs.
View on AmazonThese are optional diagnostic tools, not guaranteed fixes. As an Amazon Associate I earn from qualifying purchases.