OBD-II code · Powertrain (generic, extended)
P2521 A/C Request A Circuit High
The A/C request input A reads stuck high — typically a short to battery voltage. The ECM cannot pull the line low to read switch state, so the A/C compressor request is treated as invalid and the clutch stays disengaged.
Is it safe to drive with P2521?
Usually safe to drive in the short term. Get it diagnosed when convenient, sooner if the car drives differently.
Common causes
- Most likelyRequest wire shorted to battery voltage
- Less likelyConnector pins corroded - high contact resistance
- Less likelySupply wire pinched against B+ source
Repair at a glance
- Difficulty
- Medium
- DIY friendly
- Best left to a mechanic
- Typical labour
- 0.4–2 h
- Emissions test
- Usually unaffected
- Parts involved
- AC Request Input A
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.