Easy one-page printout for the garage or repair shop
This summary uses the existing diagnostic information shown in full below.
This code means there is a problem with the part of the car's air conditioning system that helps control the temperature. It's like when a thermostat in your house isn't working right and the temperature gets too hot or too cold.
The code indicates that the control circuit for the heat pump expansion valve 'A' is experiencing higher than normal voltage levels.
The P1D90 code is triggered when the Engine Control Module (ECM) detects a high voltage condition in the control circuit of the heat pump expansion valve 'A'. This valve is crucial for regulating the flow of refrigerant in the heat pump system, which is essential for maintaining proper cabin temperature.
• Poor air conditioning performance
• Inconsistent cabin temperature
• Check Engine Light illuminated
• Faulty heat pump expansion valve 'A'
• Wiring issues such as open or short circuits
• Malfunctioning ECM or control module
ECM: Engine Control Module
HVAC: Heating, Ventilation, and Air Conditioning
• Perform a visual inspection of the wiring and connectors for damage.
• Use a multimeter to check for proper voltage and continuity in the circuit.
• Test the heat pump expansion valve 'A' for functionality.
• Repair or replace damaged wiring or connectors.
• Replace the faulty heat pump expansion valve 'A'.
• Reprogram or replace the ECM if necessary.
• OBD-II scanner
• Multimeter
• Basic hand tools
$150 - $500
Moderate
• Honda Accord Hybrid
• Toyota Prius
• Chevrolet Volt
• Regular maintenance of the air conditioning system
• Periodic inspection of electrical connections
• Timely replacement of worn-out components
Sensor Issue
• Have the air conditioning system checked regularly.
• Address any Check Engine Light issues promptly.
Check with your vehicle manufacturer as the heat pump system might be covered under the emissions warranty.
This code has been associated with hybrid and electric vehicles that use advanced climate control systems.
Moderate – While it may not immediately affect drivability, it can lead to discomfort and further issues if left unresolved.
Always ensure repairs are performed by a qualified technician to avoid voiding warranties or causing further damage.
• Vehicle at operating temperature
• Air conditioning system activated
The heat pump expansion valve is typically located near the evaporator or within the HVAC unit in the engine bay.
Q: Can I drive with a P1D90 code?
A: Yes, but it is advisable to have it checked soon to avoid discomfort and potential further damage.
Q: Will a P1D90 code affect my fuel efficiency?
A: It might slightly affect efficiency if the air conditioning system is not functioning optimally.
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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.
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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.
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Fitment Required · Vehicle-fitment part
Relevant when EVAP diagnosis points toward purge-flow or purge-control faults.
EVAP diagnosis often includes purge-flow and valve-control faults.
Confirm the failed valve and exact fitment before buying parts.
View options on AmazonThese parts may be related to this fault category, but a code by itself does not confirm exact fitment or guarantee that replacing a part will solve the problem.