A/C Signal: Testing and Inspection

PREPARATION
Connect the special service tools (SST) to the engine control module (ECM).

Connect Special Service Tools As Shown:

1. Connect the SST engine signal monitor between the ECM and the vehicle's ECM connector by using the SST adapter harness.

View: Special Service Tool (SST)-Sheet Overlay:

2. Place the SST engine signal sheet overlay on the SST engine signal monitor.
3. Turn ignition switch ON. Turn blower switch ON.
4. Measure voltage at terminal 1Q.

Condition:--Air Conditioning Switch ON.
Voltage:--Below 2.5 Volts.

Condition:--Air Conditioning Switch OFF.
Voltage:--Battery voltage.

View: A/C Signal Path Diagram:

If readings are not as shown then inspect refrigerant pressure switch, thermoswitch, and wiring between ECM terminal 1Q (BR wire) and heater control unit terminal (G wire) from Air Conditioning Switch.