A/C Pressure Switch Circuit Troubleshooting - Without Climate Control

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 switch 5P connector.

8.Turn the ignition switch ON (II).

9.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 10.


NO - Repair open in the wire between the A/C pressure switch and the A/C switch.n


10.Turn the ignition switch OFF.

11.Test the A/C switch.

Is the A/C switch OK?


YES - Go to 12.


NO - Replace the A/C switch.n


12.Disconnect the heater fan switch 7P connector.

13.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 14.


NO - Repair open in the wire between the A/C switch and the  heater fan switch.n


14.Test the heater fan switch.

Is the heater fan switch OK?


YES - Go to 15.


NO - Replace the  heater fan switch.n

15.Check for continuity between the No. 3 terminal of the heater fan switch 7P connector and body ground.

 

Is there continuity?


YES - Go to 16.


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


16.Disconnect the evaporator temperature sensor 2P connector.

17.Measure the resistance between the No. 1 and No. 2 terminals of the evaporator temperature sensor.

 

Is the resistance within the specifications shown on the graph?


YES - Go to 18.


NO - Replace the  evaporator temperature sensor.n


18.Disconnect the negative cable from the battery.

19.Disconnect ECM/PCM connector E (31P).

20.Check for continuity between the following terminals of ECM/PCM connector E (31P) and the evaporator temperature sensor 2P connector.

E (31P): 2P: 
No. 4 No. 2 
No. 12 No. 1 

 

Is there continuity?


YES - Go to 21.


NO - Repair any open in the wire(s) between the  ECM/ PCM and the  evaporator temperature sensor.n

21.Check for continuity between the No. 12 terminal of ECM/PCM connector E (31P) and body ground.

 

Is there continuity?


YES - Repair short to body ground in the wire between the  ECM/ PCM and the evaporator temperature sensor.n


NO - Check for loose wires or poor connections at ECM/PCM connector E (31P), the evaporator temperature sensor 2P 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/ PCM, and recheck. If the symptom/indication goes away, replace the original ECM/PCM.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. 28 terminal of ECM/PCM connector E (31P) and body ground with the ECM/PCM connectors connected.

 

Is there about 5 V?


YES - Repair open in the wire between the  ECM/ PCM and the A/C pressure switch.n


NO - Check for loose wires or poor connections at ECM/PCM connector E (31P). If the connections are good, substitute a known-good  ECM/ PCM, and recheck. If the symptom/indication goes away, replace the original ECM/PCM.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