DTC B1412/12: Ambient Temperature Sensor Circuit: Procedure

1. Connect the Techstream to the DLC3.
2. Turn the ignition switch to ON and turn the Techstream main switch on.
3. Select the item below in the Data List, and read the value displayed on the Techstream.
   DATA LIST / AIR CONDITIONER
   
   

   Tester Display	Measurement Item/Range	Normal Condition	Diagnostic Note
   Ambient Temp Sensor	Ambient temperature sensor / Min.: -23.3°C (-9.94°F) Max.: 65.95°C (150.71°F)	Actual ambient temperature is displayed	Open in circuit: -23.3°C (-9.94°F) Short in circuit: 65.95°C (150.71°F)

   OK

   The display is as specified in the normal condition column.

   Result

   Result	Proceed to
   NG	A
   OK (When troubleshooting according to PROBLEM SYMPTOMS TABLE)	B
   OK (When troubleshooting according to DTC)	C

B → See step   7 

C → See step   4 

A: Go to next step 

1. Remove the cooler thermistor (ambient temperature sensor), refer to REMOVAL .
   Fig 1: Identifying Ambient Temperature Sensor

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
2. Measure the resistance according to the value(s) in the table below.

   Standard resistance

   Tester Connection	Condition	Specified Condition
   A7-1 - A7-2	10°C (50°F)	3.00 to 3.73 kΩ
   A7-1 - A7-2	15°C (59°F)	2.45 to 2.88 kΩ
   A7-1 - A7-2	20°C (68°F)	1.95 to 2.30 kΩ
   A7-1 - A7-2	25°C (77°F)	1.60 to 1.80 kΩ
   A7-1 - A7-2	30°C (86°F)	1.28 to 1.47 kΩ
   A7-1 - A7-2	35°C (95°F)	1.00 to 1.22 kΩ
   A7-1 - A7-2	40°C (104°F)	0.80 to 1.00 kΩ
   A7-1 - A7-2	45°C (113°F)	0.65 to 0.85 kΩ
   A7-1 - A7-2	50°C (122°F)	0.50 to 0.70 kΩ
   A7-1 - A7-2	55°C (131°F)	0.44 to 0.60 kΩ
   A7-1 - A7-2	60°C (140°F)	0.36 to 0.50 kΩ

   NOTE:

   • Touching the sensor even slightly may change the resistance value. Be sure to hold the connector of the sensor.
   • When measuring, the sensor temperature must be the same as the ambient temperature.

   HINT: 

   As the temperature increases, the resistance decreases (see the graph).

NG → See step   5 

OK: Go to next step 

1. Disconnect the A7 sensor connector.
   Fig 2: Identifying A7 & D37 Connector Terminals

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
2. Disconnect the D37 amplifier connector.
3. Measure the resistance according to the value(s) in the table below.

   Standard resistance

   Tester Connection	Condition	Specified Condition
   A7-1 - D37-5 (TAM)	Always	Below 1 Ω
   A7-2 - D37-13 (SG-2)	Always	Below 1 Ω
   D37-5 (TAM) - Body ground	Always	10 kΩ or higher
   D37-13 (SG-2) - Body ground	Always	10 kΩ or higher

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

OK → See step   6