P2520: Air Conditioning Request A Circuit Low
What to do
You may find the air conditioning either running when it should not, or not working at all — a shorted request line reads as a permanently pressed button, and different vehicles respond differently. If the compressor is running constantly, mention it: that costs fuel and can freeze the evaporator, which blocks the airflow and looks like a blower fault.
What this code means
The air conditioning request circuit reads below its valid range, normally a short to ground.
A shorted request line reads as a permanent request, which produces the opposite symptom from the open circuit at P2519: rather than no air conditioning, the module may be asked for the compressor constantly — including with the system switched off and in conditions where it would normally be refused.
That matters beyond comfort. The compressor engaging when it should not costs fuel, adds load at idle, and on a very cold day risks the evaporator freezing, which blocks airflow entirely and is a fault people report as a blower failure. Most modules include protections that override a stuck request, so the more common outcome is that the module ignores the line and disables the air conditioning altogether — but which happens depends on the vehicle.
Likely causes
Start here
- Wiring shorted to ground · moderate
- Faulty climate control panel or switch · moderate
- Corroded or loose connector · easy
Less common
- Damaged wiring harness · moderate
Symptoms
Components involved
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
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