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.

HINT:

In case of using the LEXUS hand- held tester, start the inspection step 1 and in case of not using the LEXUS hand-held tester, start from step 2.

Check room temp, sensor using LEXUS hand- held tester.
PREPARATION:

Connect the LEXUS hand-held tester to the DLC3.

CHECK:

Check the room temp, sensor using DATA LIST.
1. OK : Check and replace A/C ECU.
2. NG : Go to next step.
Check voltage between terminals TR and SG-2 of A/C ECU connector.
PREPARATION:

Remove A/C ECU with connectors still connected.

CHECK:
1. Turn ignition switch to ON.
2. Measure voltage between terminals TR and SG-2 of A/C ECU connector at each temperature.
OK:

Voltage :

at 25°C (77°F) : 1.8 - 2.2 V

at 40°C (104°F) : 1.2 - 1.6 V

HINT:

As the temperature increases, the voltage decreases.

Fig 1: Identifying Voltage Between Terminals TR And Sg-2 Of A/C ECU Connector
Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
1. NG : Go to step 3.
2. OK : Proceed to next circuit inspection shown on problem symptoms table (See PROBLEM SYMPTOMS TABLE ). However, if DTC B1411/11 is displayed, check and replace A/C ECU.
Check room temperature sensor.
PREPARATION:

Disconnect room temperature sensor connector.

CHECK:

Measure resistance between terminals 1 and 2 of room temperature sensor connector at each temperature.

OK:

Resistance :

at 25°C (77°F) : 1.65 - 1.75 kΩ

at 50°C (122°F) : 0.55 - 0.65 kΩ

HINT:

As the temperature increases, the resistance decreases.

Fig 2: Identifying Room Temperature Sensor
Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
1. NG : Replace room temperature sensor.
2. OK : Go to next step.
Check harness and connector between A/C ECU and room temperature 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.