KM40 - Check A/C Input

Diagnostic Trouble Code (DTC) 539 indicates the AC Clutch Supply (ACCS) input to the Powertrain Control Module (PCM) was high during Key On Engine Off (KOEO) / Key On Engine Running (KOER) Self-Test.

NOTE: Before entering this test, verify A/C selector is "OFF" (automatic transmissions in "PARK"). If A/C was on, turn "OFF" and rerun Self-Test. Quick Test Appendix (Detailed Testing Instructions)

If DTC 539 is still present, continue with this test.


- Disconnect Powertrain Control Module (PCM). Inspect for damaged or pushed out pins, corrosion, loose wires, etc. Service as necessary.

- Install breakout box, leave PCM disconnected.

- Digital Volt/Ohm Meter (DVOM) on 20 volt scale.

- Key "ON", engine "OFF".

- Measure voltage between test pin 10 at the breakout box end chassis ground.

- Is voltage greater then 1.0 volt?

Yes -- Verify operation of A/C demand switch. If OK, service short to power in A/C circuit (A/C demand or Power-to-A/C clutch). Remove breakout box. Reconnect all components. Rerun quick test. Quick Test Appendix (Detailed Testing Instructions)

No -- Replace PCM. Remove breakout box. Reconnect all components. Rerun quick test. Quick Test Appendix (Detailed Testing Instructions)