Diagnostic Aids
Perform this test when diagnosing a symptom. To prevent replacing good components, check the following non-EEC components and systems:
- Refrigerant charge.
- Low ambient temperature (less than 45°F (7°C).
NOTE:
This procedure starts with step 40). No test procedures have been omitted. Before performing this test, ensure A/C switch is off. If A/C switch was on, turn A/C off and repeat QUICK TEST.
- 40) DTC 539: Check A/C Input DTC 539 indicates ACCS input to PCM was high during KOEO/KOER SELF-TEST. Turn ignition off. Disconnect 60-pin PCM connector. Inspect terminals, and repair if damaged. Install breakout box, leaving PCM disconnected. Turn ignition on. Measure voltage between test pin No. 10 at breakout box and chassis ground. If voltage is 1.0 volt or more, verify operation of A/C demand switch. If A/C demand switch is okay, repair short to power in A/C circuit and repeat QUICK TEST. If voltage is less than 1.0 volt, replace PCM. Remove breakout box and repeat QUICK TEST.