KM70 - Check A/C Input

Diagnostic Trouble Code (DTC) 539 indicates the A/C demand input to the Powertrain Control Module (PCM) was low (A/C on) during Key On Engine Off (KOEO) Self-Test.

NOTE: Before entering this test, verify A/C selector is off. If A/C was on, rerun KOEO Self-Test. Quick Test Appendix (Detailed Testing Instructions)

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

- Key "OFF".

- A/C "OFF".

- Disconnect Low Pressure (LP) switch.

- Measure resistance between A/C demand switch side of LP switch vehicle harness connector and chassis ground.

- Is resistance greater than 10,000 ohms?

Yes -- Go to KM71. KM71 - Check Low Pressure Switch

No -- Verify operation of A/C demand switch. Refer to Heating and Air conditioning. If OK, service short to ground. Reconnect all components. Re-evaluate symptom.