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's a problem with the part of your car's heating and cooling system that controls how much refrigerant flows. It's like a valve that isn't opening or closing properly.
The code indicates an issue with the electrical circuit controlling the expansion valve in the heat pump system, which may be open or not functioning correctly.
The P1D91 code is triggered when the Powertrain Control Module (PCM) detects an open circuit or malfunction in the control circuit for the Heat Pump Expansion Valve 'A'. This valve is crucial for regulating the flow of refrigerant in the vehicle's heat pump system, which is part of the climate control system.
• Poor heating or cooling performance
• Check engine light on
• Unusual noises from the HVAC system
• Faulty expansion valve
• Damaged wiring or connectors
• Faulty PCM
PCM: Powertrain Control Module
HVAC: Heating, Ventilation, and Air Conditioning
• Inspect the wiring and connectors for damage or corrosion.
• Test the expansion valve for proper operation.
• Check the PCM for any faults or errors.
• Replace or repair damaged wiring or connectors.
• Replace the faulty expansion valve.
• Reprogram or replace the PCM if necessary.
• Multimeter
• OBD-II scanner
• Screwdriver set
$150 - $500
Moderate
• Honda Accord Hybrid
• Toyota Prius
• Chevrolet Volt
• Regular maintenance of the HVAC system
• Routine inspection of electrical connections
• Timely replacement of faulty components
Sensor Issue
• Have your vehicle inspected by a professional if you notice poor heating or cooling.
• Avoid using the HVAC system until the issue is resolved to prevent further damage.
Check with your vehicle manufacturer or warranty provider to see if this issue is covered under warranty.
This code has become more common with the increased use of hybrid and electric vehicles that use heat pump systems for climate control.
Moderate – It affects comfort but not immediate drivability.
Driving with this code may not be illegal, but it can affect comfort and efficiency. Always ensure your vehicle is safe to drive.
• Vehicle at operating temperature
• HVAC system engaged
The expansion valve is typically located near the evaporator in the HVAC system, often behind the dashboard.
Q: Can I drive with a P1D91 code?
A: Yes, but it may affect your vehicle's heating and cooling performance.
Q: How do I reset the P1D91 code?
A: After repairs, use an OBD-II scanner to clear the code. If the issue is fixed, it should not return.
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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.