XB40 - Continuous Code 578: Clear and Try to Regenerate Code

Continuous Memory Diagnostic Trouble Code (DTC) 578 indicates the A/C Pressure (ACP) sensor VREF circuit is short to ground. This could be due to a hard fault or an intermittent condition.

Possible causes:
- ACP sensor VREF circuit short to ground.
- Damaged ACP sensor.
- Damaged Variable Control Relay Module (VCRM).

- Clear continuous memory. Clearing Diagnostic Trouble Codes

- Start engine, wait 15 seconds.

- Engine "OFF".

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

- Is Continuous Memory DTC 578 present?

Yes -- DTC 578 is a hard fault. Go to XB41. XB41 - Check ACP Sensor

No -- DTC 578 is intermittent. Go to XB44. XB44 - Check ACP VREF For Intermittent Short to Ground