<ul> <li><b>Engine Light ON (or Service Engine Soon Warning Light)</b>: The illumination of the engine light indicates a detected issue with the A/C Request 'A' Circuit. This could be due to a high voltage condition in the circuit.</li> <li><b>A/C System Malfunction</b>: The air conditioning system may not function properly, potentially blowing warm air or not activating at all. This is often linked to issues in the A/C Request 'A' Circuit.</li> <li><b>Erratic A/C Performance</b>: The air conditioning may work intermittently or show inconsistent performance, which can be caused by electrical issues in the A/C Request 'A' Circuit.</li> </ul>

<ul><li>Low refrigerant levels can cause the A/C system to malfunction, leading to high circuit readings.</li><li>Excessive refrigerant can also disrupt the A/C system's balance, triggering the error code.</li><li>A faulty Low Side Pressure Sensor may provide incorrect readings, causing the system to register a high circuit.</li><li>An open or shorted Low Side Pressure Sensor harness can lead to improper sensor function and high circuit errors.</li><li>Poor electrical connections in the Low Side Pressure Sensor circuit can result in intermittent or incorrect signals, causing the error code.</li></ul>

<ul> <li><b>Initial Scan</b>: Use an OBD-II scanner to confirm the presence of DTC P2521 and check for any additional codes that may be related.</li> <li><b>Visual Inspection</b>: Inspect the A/C request circuit wiring and connectors for any signs of damage, corrosion, or disconnection.</li> <li><b>Check A/C Request Signal</b>: Using a multimeter, measure the voltage at the A/C request signal wire. Ensure it matches the manufacturer's specifications.</li> <li><b>Inspect A/C Control Module</b>: Verify the functionality of the A/C control module. Check for any signs of internal failure or damage.</li> <li><b>Test A/C Relay</b>: Test the A/C relay for proper operation. Replace if it is found to be faulty.</li> <li><b>Check Ground Connections</b>: Ensure all ground connections related to the A/C system are secure and free of corrosion.</li> <li><b>Verify A/C Compressor Operation</b>: Confirm that the A/C compressor engages when the A/C is requested. If not, inspect the compressor and related components.</li> <li><b>Re-scan and Verify Repair</b>: After performing necessary repairs, clear the DTC and re-scan the system to ensure the code does not return.</li></ul>

<p>The DTC code P2521 indicates an issue with the A/C Request 'A' Circuit High. This is a minor issue.</p><ul><li><b>Immediate Actions:</b> Check the A/C request signal circuit for any loose connections or damaged wiring.</li><li><b>Potential Risks:</b> Delayed repair may result in reduced A/C performance, but it does not pose a significant risk to vehicle operation.</li></ul>