Easy one-page printout for the garage or repair shop
This summary uses the existing diagnostic information shown in full below.
This code means that the computer in your car thinks the temperature sensor for the heat pump is reading too high. It's like when a thermometer says it's really hot, but it might be broken.
The P1D77 code is triggered when the vehicle's powertrain control module (PCM) detects a high voltage signal from the heat pump temperature sensor 'C'. This indicates the sensor is reading a temperature that is higher than expected.
The heat pump temperature sensor 'C' is responsible for monitoring the temperature of the heat pump system in vehicles equipped with such technology. A high circuit signal typically means the sensor is outputting a voltage higher than the normal operating range, which the PCM interprets as an excessively high temperature reading.
• Check engine light illuminated
• Reduced heating or cooling efficiency
• Inconsistent cabin temperature
• Faulty heat pump temperature sensor
• Wiring issues such as short circuits or open circuits
• Faulty PCM (rare)
PCM: Powertrain Control Module
OBD-II: On-Board Diagnostics, Second Generation
• Use an OBD-II scanner to confirm the code
• Inspect the heat pump temperature sensor and its wiring
• Test the sensor's voltage and resistance
• Replace the faulty heat pump temperature sensor
• Repair or replace damaged wiring
• Reprogram or replace the PCM if necessary
• OBD-II scanner
• Multimeter
• Wiring repair kit
$100 - $300
Moderate
• Honda Accord Hybrid
• Toyota Prius
• Chevrolet Volt
• Regularly inspect and maintain the vehicle's electrical system
• Ensure the heat pump system is serviced according to manufacturer guidelines
• Avoid overloading the vehicle's electrical system
Sensor Issue
• Do not ignore the check engine light; have the vehicle inspected promptly
• Consider routine maintenance to prevent sensor failures
• Consult a professional mechanic for accurate diagnosis
Check with the vehicle manufacturer for warranty coverage on emissions-related components.
This code has been more prevalent in hybrid and electric vehicles due to their advanced heating and cooling systems.
Moderate – While the vehicle may still operate, efficiency and comfort can be affected.
Driving with a faulty sensor can lead to inefficient vehicle operation and potential damage to the system.
• Vehicle at operating temperature
• Heat pump system engaged
The heat pump temperature sensor is typically located near the heat pump unit, often in the engine bay or under the vehicle.
Q: Can I drive with a P1D77 code?
A: It's possible to drive, but it's not recommended as it may affect your vehicle's efficiency and comfort.
Q: How can I prevent this code from occurring?
A: Regular maintenance and inspections can help prevent sensor issues.
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