Inspection Procedure

WARNING: This page is about a different car, the 2003 Lexus LS 430. However, it is still accessible from the selected car via links, so may be relevant.

Check voltage between terminals PRS and SG-5 of A/C ECU connector.
PREPARATION:
1. Remove A/C ECU with connectors still connected.
2. Install manifold gauge set (See MANIFOLD GAUGE SET ).
CHECK:
1. Turn ignition switch to ON.
2. Check voltage between terminals PRS and SG-5 of A/C ECU connector.
OK:

The voltage depends on the refrigerant pressure as shown in the chart.

Fig 1: Identifying Terminals PRS And Sg-5 Of A/C ECU Connector
Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
1. OK : Proceed to next circuit inspection shown on problem symptoms table (See PROBLEM SYMPTOMS TABLE ).
2. NG : Go to next step.
Check pressure sensor.
PREPARATION:
1. Disconnect pressure sensor connector.
2. Install manifold gauge set (See MANIFOLD GAUGE SET ).
CHECK:
1. Connect the positive (+) lead from the three 1.5 V dry cell batteries to terminal 3 and negative (-) lead to terminal 1.
2. Check voltage between terminals 2 and 1 of pressure sensor.
OK:

The voltage depends on the refrigerant pressure as shown in the chart.
1. NG : Replace pressure sensor.
  
  Fig 2: Identifying Pressure Sensor
  Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
2. OK : Go to next step.
Check harness and connector between A/C ECU and pressure sensor (See HOW TO USE THE DIAGNOSTIC CHART AND INSPECTION PROCEDURE ).
1. NG : Repair or replace harness or connector.
2. OK : Check and replace A/C ECU.