Air Conditioning System

AIR CONDITIONING: AIR CONDITIONING SYSTEM: B1412/12: Ambient Temperature Sensor Circuit

DTC B1412/12 - Ambient Temperature Sensor Circuit

DESCRIPTION

1. 2GR-FSE:
The ambient temperature sensor is installed in the front part of the condenser to detect the ambient temperature and control the air conditioner "AUTO" mode. The sensor connected to the ECM detects fluctuations in the ambient temperature. This data is used for controlling the room temperature. The sensor sends a signal to the A/C amplifier via the ECM. The resistance of the ambient temperature sensor changes in accordance with the ambient temperature. As the temperature decreases, the resistance increases. As the temperature increases, the resistance decreases.
The ECM applies voltage (5 V) to the ambient temperature sensor and reads voltage changes as the resistance of the ambient temperature sensor changes. The ECM sends the read signal to the A/C amplifier via CAN and body multiplex communications.
2. 1UR-FSE:
The ambient temperature sensor is installed in front of the condenser to detect the ambient temperature which is used to control the air conditioner "AUTO" mode. This sensor is connected to the A/C amplifier and detects fluctuations in the ambient temperature. This data is used for controlling the cabin temperature. The sensor sends a signal to the A/C amplifier. The resistance of the ambient temperature sensor changes in accordance with the ambient temperature. As the temperature decreases, the resistance increases. As the temperature increases, the resistance decreases.
The A/C amplifier applies voltage (5 V) to the ambient temperature sensor and reads voltage changes as the resistance of the ambient temperature sensor changes.






WIRING DIAGRAM

1. 2GR-FSE:





2. 1UR-FSE:





INSPECTION PROCEDURE
HINT:
- 2GR-FSE: Start inspection from step 1.
- 1UR-FSE: Start inspection from step 3.

PROCEDURE

1. CHECK MULTIPLEX COMMUNICATION SYSTEM (BEAN)
(a) Use the Techstream to check if the multiplex communication system (BEAN) is functioning normally.
Result:






B -- GO TO MULTIPLEX COMMUNICATION SYSTEM (BEAN)
A -- Continue to next step.

2. CHECK CAN COMMUNICATION SYSTEM
(a) Use the Techstream to check if the CAN communication system is functioning normally.
Result:






B -- GO TO CAN COMMUNICATION SYSTEM
A -- Continue to next step.

3. READ VALUE USING TECHSTREAM
(a) Connect the Techstream to the DLC3.
(b) Turn the engine switch on (IG).
(c) Turn the Techstream on.
(d) Select the item below in the Data List, and read the display on the Techstream.

Data List / Air Conditioner:





OK:
The display is as specified in the normal condition.
Result:






C -- REPLACE AIR CONDITIONING AMPLIFIER
B -- PROCEED TO NEXT CIRCUIT INSPECTION SHOWN IN PROBLEM SYMPTOMS TABLE
A -- Continue to next step.

4. INSPECT AMBIENT TEMPERATURE SENSOR




(a) Remove the ambient temperature sensor.
(b) Measure the resistance of the sensor.
Standard resistance:





NOTICE:
- 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.
HINT: As the temperature increases, the resistance decreases (see the graph).

NG -- REPLACE AMBIENT TEMPERATURE SENSOR
OK -- Continue to next step.

5. CONFIRM MODEL
Result:






B -- CHECK HARNESS AND CONNECTOR (AMBIENT TEMPERATURE SENSOR - A/C AMPLIFIER)
A -- Continue to next step.

6. CHECK HARNESS AND CONNECTOR (AMBIENT TEMPERATURE SENSOR - ECM)




(a) 2GR-FSE
(1) Disconnect the B5 ambient temperature sensor connector.
(2) Disconnect the A6 ECM connector.
(3) Measure the resistance according to the value(s) in the table below.
Standard resistance:






NG -- REPAIR OR REPLACE HARNESS AND CONNECTOR
OK -- REPLACE ECM
7. CHECK HARNESS AND CONNECTOR (AMBIENT TEMPERATURE SENSOR - A/C AMPLIFIER)




(a) 1UR-FSE
(1) Disconnect the B5 ambient temperature sensor connector.
(2) Disconnect the K52 A/C amplifier connector.
(3) Measure the resistance according to the value(s) in the table below.
Standard resistance:






NG -- REPAIR OR REPLACE HARNESS AND CONNECTOR
OK -- REPLACE AIR CONDITIONING AMPLIFIER