XB52 - Clear and Attempt to Regenerate DTC

- Clear continuous memory. Clearing Diagnostic Trouble Codes

- Attempt to reset Diagnostic Trouble Code (DTC) 579 by performing the following:

(1) Start engine.

(2) A/C "ON", wait 20 seconds after A/C clutch engagement is heard ("click").

(3) A/C "OFF", wait 5 seconds.

(4) Repeat steps 2 and 3 four more times (a total of five A/C clutch engagements, with each engagement lasting about 20 seconds, must be seen by the Variable Control Relay Module (VCRM) during the same power-up to set DTC 579 for insufficient A/C pressure change).

- A/C "OFF".

- Engine "OFF".

- Rerun Key On Engine Off (KOEO) Self-Test. Quick Test Appendix (Detailed Testing Instructions)

- Is Continuous Memory DTC 579 present?

Yes -- DTC 579 is a hard fault. Go to XB53. XB53 - Check A/C System Pressure Change

No -- The A/C Pressure (ACP) sensor is now able to detect an A/C system pressure change. Either an intermittent ACP sensor circuit fault exists, or an A/C system intermittent or marginal mechanical condition exists. Go to XB66. XB66 - Does the A/C Appear to Cool Properly