P2520: A/C Request A Circuit Low

What it means

The A/C request A circuit signal is below the expected limit. The code does not establish the request state or resulting A/C behavior.

At a glance

• Usually lights the check-engine light

How it works

The A/C request A circuit carries a request signal associated with air-conditioning operation. The control module monitors this circuit and sets P2520 when its signal falls below the expected limit; this does not establish whether the A/C is being requested or how the system responds.

Common causes

Most likely first.

1. Request wire shorted to ground
2. Connector pins corroded - high contact resistance
3. Harness chafing through insulation

Symptoms

• A/C operation may be unavailable or inconsistent
• A/C request may not be recognized

How to diagnose it

1. Record freeze-frame data and check for related HVAC or module codes to identify when the A/C request A fault appeared.
2. Compare the scan-tool A/C request A status with the control setting while switching A/C on and off.
3. Inspect the request A wire and its connectors for chafing, corrosion, loose pins, or contact with ground.
4. Using the wiring diagram, check the request A circuit for a short to ground and test continuity with the circuit isolated as specified by the manufacturer.
5. If the wire and terminals pass, check whether the HVAC module is sending request A and whether the receiving module registers it.

Common fixes

• Repair chafed request A wiring that is contacting ground.
• Clean or repair corroded or loose request A connector terminals.
• Repair an open or damaged section of the request A wire.
• Repair a faulty HVAC control or module only after circuit tests identify it.

Can I keep driving?

You can generally drive if the vehicle otherwise operates normally, but A/C may be unavailable or inconsistent. The fault by itself does not establish that the engine or braking system is unsafe.