| 1. | Disconnect the A/C pressure switch 2P connector. |
| 2. | Turn the ignition switch ON (II). |
| 3. | Measure the voltage between the No. 2 terminal of the A/C pressure switch 2P connector and body ground.
Is there about 5 V? YES - Go to 4. NO - Go to 22. |
| 4. | Turn the ignition switch OFF. |
| 5. | Check for continuity between the No. 1 and No. 2 terminals of the A/C pressure switch.
Is there continuity? YES - Go to 6. NO - Go to 27. |
| 6. | Reconnect the A/C pressure switch 2P connector. |
| 7. | Disconnect the A/C thermostat 3P connector. |
| 8. | Turn the ignition switch ON (II). |
| 9. | Measure the voltage between the No. 3 terminal of the A/C thermostat 3P connector and body ground.
Is there battery voltage? YES - Go to 10. NO - Repair open in the wire between the No. 22 fuse in the under-dash fuse/relay box and the A/C thermostat.n |
| 10. | Turn the ignition switch OFF. |
| 11. | Test the A/C thermostat. Is the A/C thermostat OK? YES - Go to 12. NO - Replace the A/C thermostat.n |
| 12. | Reconnect the A/C thermostat 3P connector. |
| 13. | Disconnect the A/C switch 5P connector. |
| 14. | Turn the ignition switch ON (II). |
| 15. | Measure the voltage between the No. 2 terminal of the A/C switch 5P connector and body ground.
Is there about 5 V? YES - Go to 16. NO - Repair open in the wire between the A/C thermostat and the A/C switch.n |
| 16. | Turn the ignition switch OFF. |
| 17. | Test the A/C switch. Is the A/C switch OK? YES - Go to 18. NO - Replace the A/C switch.n |
| 18. | Disconnect the heater fan switch 7P connector. |
| 19. | Check for continuity between the No. 1 terminal of the A/C switch 5P connector and the No. 6 terminal of the heater fan switch 7P connector.
Is there continuity? YES - Go to 20. NO - Repair open in the wire between the A/C switch and the heater fan switch.n |
| 20. | Test the heater fan switch. Is the heater fan switch OK? YES - Go to 21. NO - Replace the heater fan switch.n |
| 21. | Check for continuity between the No. 3 terminal of the heater fan switch 7P connector and body ground.
Is there continuity? YES - Check for loose wires or poor connections at ECM connector E (40P), the A/C thermostat connector, the A/C pressure switch 2P connector, the A/C switch 5P connector and at the heater fan switch 7P connector. If the connections are good, substitute a known-good ECM, and recheck. If the symptom/indication goes away, replace the original ECM.n NO - Check for an open in the wire between the heater fan switch and body ground. If the wire is OK, check for poor ground at G402.n |
| 22. | Turn the ignition switch OFF. |
| 23. | Reconnect the A/C pressure switch 2P connector. |
| 24. | Make sure the A/C switch is OFF. |
| 25. | Turn the ignition switch ON (II). |
| 26. | Measure the voltage between the No. 40 terminal of ECM connector E (40P) and body ground with the ECM connectors connected.
Is there about 5 V? YES - Repair open in the wire between the ECM and the A/C pressure switch.n NO - Check for loose wires or poor connections at ECM connector E (40P). If the connections are good, substitute a known-good ECM, and recheck. If the symptom/indication goes away, replace the original ECM.n |
| 27. | Check for proper A/C system pressure. Is the pressure within specifications? YES - Replace the A/C pressure switch.n NO - Repair the A/C pressure problem.n |