P2520
A/C Request A Circuit Low
A/C request signal
Generic OBD-II
Low
What it means
P2520 means the air-conditioning request signal to the engine computer is reading low (typically shorted to ground). The ECU uses this signal to engage the compressor and raise idle when A/C is on, so the fault is a wiring or switch problem in the A/C request circuit — it doesn't affect whether the engine starts or runs.
Low
Can I keep driving? Safe to drive — the engine runs normally. The main effect is that the air conditioning may not engage or the idle may not compensate when A/C is on.
Common symptoms
What you'll notice
- Check-engine light on
- Air conditioning not engaging or working intermittently
- Idle doesn't rise to compensate when A/C is switched on
- No noticeable change to how the engine drives otherwise
Common causes
Most likely first
- Short to ground in the A/C request signal wiringLikely
- Faulty A/C pressure switch or HVAC control sending the requestCommon
- Corroded or loose connector in the request circuitCommon
- Faulty HVAC / body control moduleLess often
How to diagnose & fix
Work through it in order
- Read freeze-frame and check the live A/C request signal with the A/C off and on.
- Inspect the request-circuit wiring and connectors for a short to ground or corrosion.
- Test the A/C pressure switch and HVAC request output for correct operation.
- Confirm the ECM sees the request change when A/C is commanded on.
- Repair the shorted wire or replace the failed switch/module, then clear and re-test.
FAQ
Quick answers
Is it safe to drive with P2520?+
Yes. This is an A/C request signal fault, not an engine-running problem. At most the air conditioning won't work properly until it's repaired.
Can I just clear P2520?+
It returns while the wiring or switch is faulty. Clearing it only helps confirm whether the fault is still active.
Related codes
Often seen with P2520
Read & clear P2520 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX