A/C Pressure Switch Circuit Troubleshooting (Type S M/T Model)

WARNING: This page is about a different car, the 2003 Acura 3.2CL and 2002 Acura 3.2CL. However, it is still accessible from the selected car via links, so may be relevant.

Disconnect the A/C pressure switch 2P connector.
Turn the ignition switch ON (II).
Measure the voltage between the No. 2 terminal of the A/C presure switch 2P connector and body ground.

Fig 1: Measuring Voltage Between The A/C Presure Switch 2P Connector And Body Ground
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there about 5 V ?
1. YES : Go to step 4.
2. NO : Go to step 10.
Turn the ignition switch OFF.
Check for continuity between the No. 1 and No. 2 terminals of the A/C pressure switch.

Fig 2: Checking Continuity Between The No. 1 And No. 2 Terminals Of The A/C Pressure Switch
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there continuity ?
1. YES : Go to step 6.
2. NO : Go to step 11.
Reconnect the A/C pressure switch 2P connector.
Disconnect climate control unit connector B (20P).
Turn the ignition switch ON (II).
Measure the voltage between the No. 11 terminal of climate control unit connector B (20P) and body ground.

Fig 3: Measuring Voltage Between The Climate Control Unit Connector B (20P) And Body Ground
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there about 5 V ?
1. YES : Check for loose wires or poor connections at climate control unit connector B (20P) and at the A/C pressure switch 2P connector. If the connections are good, substitute a known-good climate control unit, and recheck. If the symptom/ indication goes away, replace the original climate control unit.
2. NO : Repair open in the wire between the climate control unit and the A/C pressure switch.
Using a Backprobe Set, measure the voltage between the No. 21 terminal of ECM connector A (31P) and body ground with the ECM connectors connected.

Fig 4: Measuring Voltage Between The ECM Connector A (31P) And Body Ground (ECM Connectors Connected)
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there about 5 V ?
1. YES : Repair open in the wire between the ECM and the A/C pressure switch.
2. NO : Check for loose wires or poor connections at ECM connector A (31P). If the connections are good, substitute a known-good ECM, and recheck. If the symptom/indication goes away, replace the original ECM.
Check for proper A/C system pressure.
Is the pressure within specifications ?
1. YES : Replace the A/C pressure switch.
2. NO : Repair the A/C pressure problem.