Easy one-page printout for the garage or repair shop
This summary uses the existing diagnostic information shown in full below.
The car's air conditioning system has a sensor that checks how hot or cold it is inside the compressor. This sensor is saying it's too cold, which might mean something is wrong.
The code indicates that the internal temperature sensor 'B' in the electric A/C compressor control module is reading a temperature that is lower than expected.
The P1D21 code is triggered when the Electric A/C Compressor Control Module detects that the internal temperature sensor 'B' is reporting a temperature reading that is below the acceptable range. This could indicate a fault in the sensor itself, a wiring issue, or a problem with the compressor's operation.
• Air conditioning not working properly
• Unusual noises from the A/C system
• A/C system shutting off unexpectedly
• Faulty internal temperature sensor 'B'
• Wiring issues or poor connections
• Faulty electric A/C compressor control module
Compressor: A device that increases the pressure of a gas by reducing its volume.
Sensor: A device that detects or measures a physical property and records, indicates, or otherwise responds to it.
• Check for any other related error codes.
• Inspect the wiring and connections to the temperature sensor.
• Test the temperature sensor for proper operation.
• Repair or replace faulty wiring or connectors.
• Replace the internal temperature sensor 'B'.
• Replace the electric A/C compressor control module if necessary.
• OBD-II scanner
• Multimeter
• Basic hand tools
$200 - $600
Moderate
• Honda Accord
• Honda Civic
• Acura MDX
• Regular maintenance of the A/C system
• Check and replace sensors as needed
• Ensure proper electrical connections
Sensor Issue
• Get the A/C system checked by a professional.
• Avoid using the A/C until the issue is resolved.
Check if the vehicle's warranty covers the A/C system components.
This code has been associated with issues in vehicles equipped with electric A/C compressors, particularly in models from the early 2010s.
Moderate – While the vehicle is still drivable, the A/C system may not function properly, which can be uncomfortable in hot weather.
Driving with a malfunctioning A/C system is generally safe, but it can lead to discomfort and reduced visibility if the defogger is affected.
• Vehicle is running and A/C system is activated.
• Ambient temperature is within normal operating range.
The electric A/C compressor is typically located in the engine bay, near the front of the vehicle.
Q: Can I drive my car with this code?
A: Yes, but the A/C may not work properly, which could be uncomfortable in hot weather.
Q: Will fixing this code improve my car's performance?
A: It will improve the comfort of your car by ensuring the A/C works properly, but it won't affect engine performance.
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