Inspection Procedure

WARNING: This page is about a different car, the 2007 Toyota Land Cruiser. However, it is still accessible from the selected car via links, so may be relevant.

CHECK AIR CONDITIONING AMPLIFIER
1. Remove the A/C amplifier with the connectors still connected.
2. Turn the ignition switch ON.
3. Measure the voltage between terminals TAM (A46-7) and FRSG (A46-18) of the A/C amplifier connector at each temperature.
  Standard voltage: 1.35 to 1.75 V at 25°C (77°F)
  
  0.85 to 1.25 V at 40°C (104°F)
  
  HINT:
  - As the temperature increases, the voltage decreases.
  - However, if DTC 12 is displayed, check and replace the A/C amplifier.
    
    Fig 1: Measuring Voltage Between Terminals TAM (A46-7) & FRSG (A46-18) Of A/C Amplifier Connector
    Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
OK: REPLACE AIR CONDITIONING AMPLIFIER

NG: GO TO NEXT STEP
INSPECT AMBIENT TEMPERATURE SENSOR
1. Disconnect the A1 ambient temperature sensor connector.
2. Measure the resistance between terminals 1 and 2 of the ambient temperature sensor connector at each temperature.
  Standard resistance: 1.6 to 1.8 kΩ at 25°C (77°F):
  
  0.5 to 0.7 kΩ at 40°C (104°F)
  
  HINT:
  
  As the temperature increases, the resistance decreases.
  
  NOTE: When installing the ambient temperature sensor, be sure to connect the sensor connector before connecting the battery.
NG: REPLACE AMBIENT TEMPERATURE SENSOR

Fig 2: Identifying A1 Ambient Temperature Sensor Terminals
Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

OK: GO TO NEXT STEP
CHECK WIRE HARNESS (AIR CONDITIONING AMPLIFIER - AMBIENT TEMPERATURE SENSOR)
NG: REPAIR OR REPLACE HARNESS AND CONNECTOR

OK: REPLACE AIR CONDITIONING AMPLIFIER