DTC B1412/12: Ambient Temperature Sensor Circuit: Procedure

1. Connect the Techstream to the DLC3.
2. Turn the ignition switch to ON.
3. Turn the Techstream on.
4. Enter the following menus: Body Electrical / Air Conditioner / Data List / Ambient Temp Sensor.
5. According to the display on the Techstream, read the 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 circuit:-23.3°C (-9.94°F) Short circuit: 65.95°C (150.71°F)

   OK

   The display is as specified in the normal condition.

   RESULT
   
   

   Result	Proceed to
   NG	A
   OK (When troubleshooting according to Problem Symptoms Table)	B
   OK (When troubleshooting according to the DTC output)	C

B → See step   4 

C → See step   5 

A: Go to next step 

1. Remove the thermistor assembly (ambient temperature sensor). Refer to REMOVAL .
   Fig 1: Identifying Ambient Temperature Sensor With Temperature Graph

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

   HINT: 

   • Even slightly touching the sensor 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.
   • As the temperature increases, the resistance decreases (see the graph).
3. Reinstall the thermistor assembly (ambient temperature sensor).

NG → See step   6 

OK: Go to next step 

1. Disconnect the A18 thermistor assembly (ambient temperature sensor) connector.
   Fig 2: Identifying A18 Ambient Temperature Sensor And H24 Air Conditioning Amplifier Connectors

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
2. Disconnect the H24 air conditioning amplifier connector.
3. Measure the resistance according to the value(s) in the table below.

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   A18-1 - H24-5 (TAM)	Always	Below 1 Ω
   A18-2 - H24-13 (SG-2)	Always	Below 1 Ω
   A18-1 or H24-5 (TAM) - Body ground	Always	10 kΩ or higher
   A18-2 or H24-13 (SG-2) - Body ground	Always	10 kΩ or higher

4. Reconnect the air conditioning amplifier connector.
5. Reconnect the thermistor assembly (ambient temperature sensor) connector.

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

OK → See step   7