Diagnostic Trouble Code

P2520

A/C Request "A" Circuit Low — Generic OBD-II

What the code means

The control system has detected a lower-than-expected signal in the A/C request circuit.

The generic OBD-II definition of P2520 is A/C Request "A" Circuit Low.

This relates to the electrical request used by the air-conditioning or climate-control system to communicate an A/C request to the relevant control system.

A low-circuit fault does not automatically identify the A/C compressor as the failed component. The request signal and associated circuitry should be checked first.

Possible causes

What could cause this P2520 fault?

Damaged or open wiring

Short to ground in the A/C request circuit

Poor or corroded electrical connection

A/C switch or climate-control input fault

Power supply or ground problem

Related fuse or relay fault

Climate-control module fault

Control-module input fault

Diagnostic approach

What should you check?

1. Confirm the fault description. Make sure the diagnostic equipment actually reports A/C Request "A" Circuit Low rather than another manufacturer-specific P2520 definition.
2. Read all related fault codes. Check the engine, climate-control and relevant body-control systems for additional faults.
3. Check A/C operation. Establish whether an A/C request is being recognised and whether the system attempts to operate.
4. Inspect the electrical circuit. Check wiring, connectors, power supplies and grounds associated with the A/C request signal.
5. Measure rather than guess. Use wiring information and appropriate electrical tests to establish why the request signal is low before replacing components.

A useful thing to remember

Always use the exact description reported by the vehicle or diagnostic equipment alongside the code number itself.