P2523: A/C Request B Circuit Low

What it means

The A/C request B 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 B circuit carries a designated air-conditioning request signal between vehicle modules. The control module monitors request B and sets P2523 when the signal falls below the expected limit; it does not establish whether request B is active or how the A/C 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 B 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 request B low-signal fault appeared.
2. Compare scan-tool request B status with the available A/C controls while changing those settings.
3. Inspect the request B wire and connectors for chafing, corrosion, loose pins, or contact with ground.
4. Using the wiring diagram, check for a short to ground and test request B wire continuity with the circuit isolated as specified by the manufacturer.
5. If the wiring passes, check whether the HVAC module is sending request B and whether the receiving module registers it.

Common fixes

• Repair chafed request B wiring that is contacting ground.
• Clean or repair corroded or loose request B connector terminals.
• Repair an open or damaged request B 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 and request B may not be recognized. The code alone does not indicate an engine or brake fault.