B1412

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

DTC B1412 - Ambient Temperature Sensor Circuit

DESCRIPTION

The ambient temperature sensor is installed in the front part of the condenser to detect the ambient temperature and control the heater and air conditioner "AUTO" function. The sensor connected to the ECM detects fluctuation in the ambient temperature that is used for controlling the room temperature. The sensor sends a signal to the air conditioning 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 air conditioning amplifier via CAN and body multiplex communications.






WIRING DIAGRAM





INSPECTION PROCEDURE

PROCEDURE

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

Air conditioning amplifier





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.

2. CHECK ECM (TAM VOLTAGE)




(a) Remove the ECM with connectors still connected.
(b) Measure the voltage of the wire harness side connectors.
Standard voltage:





HINT: As the temperature increases, the voltage decreases.

Result





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

3. 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.

4. CHECK WIRE HARNESS (AMBIENT TEMPERATURE SENSOR - ECM)




(a) Disconnect the A6 sensor connector.
(b) Disconnect the E4 and E7 ECM connectors.
(c) Measure the resistance of the wire harness side connectors.
Standard resistance:






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