Refrigerant Pressure Sensor Signal Invalid
The refrigerant pressure sensor has a faulty signal.
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What it means (plain English)
The refrigerant pressure sensor is supposed to send the pressure level of the refrigerant in the air conditioning system to the computer. When it says there's no pressure or an unrealistically high pressure, something is wrong with the sensor or the wiring. You should see pressures between 20-45 psi when it's running properly.
What the computer is actually seeing
The computer is detecting an invalid signal from the refrigerant pressure sensor, which can mean the voltage signal is outside the expected range, typically between 0.5V to 4.5V based on the pressure input.
What a healthy reading looks like
Expected refrigerant pressure should be between 20 to 45 psi on the high side during regular operation.
Guided diagnostic — the DiagCoach way
Don't just throw parts at it. Walk through these in order — each step tells you whether to keep going or stop and fix what you found.
- 11. Check the refrigerant level; if it's low, add the correct amount before testing further.
- 22. Inspect the wiring and connectors to the refrigerant pressure sensor for damage or corrosion.
- 33. Use a scan tool to monitor the refrigerant pressure sensor data while the system is operating; confirm the readings match expected values when the AC is on.
- 44. If readings are erratic or out of range, replace the refrigerant pressure sensor and retest.
- 55. If the issue persists, test the HVAC control module for fault codes and functionality.
Common causes
- Faulty refrigerant pressure sensor
- Wiring issues or poor connections
- Incorrect refrigerant level (over or under)
- Faulty HVAC control module
Typical repair cost
$$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
Yes, but the AC will not function properly, and you may be uncomfortable in hot weather.
Will the code come back after resetting?
It can if the underlying issue isn't fixed, like a bad sensor or wiring.
Why does this code pair with SPN 4574?
Both codes relate to refrigerant pressure issues, indicating multiple faults in the same system.
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