Inspection Procedure

WARNING: This page is about a different car, the 2004 Lexus ES 330. However, it is still accessible from the selected car via links, so may be relevant.

INSPECT COOLER (AMBIENT TEMP. SENSOR) THERMISTOR
1. Remove cooler (ambient temp. sensor) thermistor.
2. Measure resistance between terminals 1 and 2 of cooler (ambient temperature sensor) thermistor connector at each temperature.
  Standard
  
  Fig 1: Identifying Cooler (Ambient Temperature Sensor) Thermistor Connector Terminals
  Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
  
  Fig 2: Identifying Tester Connection Specified Condition Chart
  Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
NOTE: Even slightly touching the sensor may change the resistance value. Be sure to hold the connector of the sensor.

HINT: As the temperature increases, the resistance decreases (see the chart below).

Fig 3: Identifying Graphic Of Resistance (Ambient Temperature Sensor Circuit)
Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

NG: REPLACE COOLER (AMBIENT TEMP. SENSOR) THERMISTOR

OK: Go to next step.
CHECK HARNESS AND CONNECTOR (COOLER (AMBIENT TEMP.SENSOR) THERMISTOR AND CLOCK ASSY)
NG: REPAIR OR REPLACE HARNESS OR CONNECTOR

OK: CHECK AND REPLACE HEATER CONTROL HOUSING SUB-ASSY