What are the common causes of P2521?

Short to power in the A/C request A circuit. Failed A/C request switch or sensor. Corroded A/C request A connector. Faulty A/C control module holding the request high.

Read A/C request A circuit voltage on a scan tool. Check the A/C request A signal wire for a short to power. Test the A/C request switch or sensor operation. Inspect the A/C request A connector for corrosion. Replace the A/C request switch or sensor if it reads high. Clear the code and retest.

P2521

A/C Request A Circuit High

System: Speed and idle control (P code)
Lamp: Check Engine Light
Category: Powertrain - Computer and Auxiliary Controls

What it means

P2521 means A/C Request A Circuit High.

Check these first

Short to power in the A/C request A circuit
Failed A/C request switch or sensor
Corroded A/C request A connector
Faulty A/C control module holding the request high

What to do next

Read A/C request A circuit voltage on a scan tool
Check the A/C request A signal wire for a short to power
Test the A/C request switch or sensor operation
Inspect the A/C request A connector for corrosion
Replace the A/C request switch or sensor if it reads high
Clear the code and retest

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Updated

Generic SAE J2012 definition. Last updated 2026-10-10.