B1412

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

DTC B1412/12 - Ambient Temperature Sensor Circuit

DESCRIPTION

The A/C 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 hybrid vehicle control ECU detects fluctuation in the ambient temperature that is used for controlling the room temperature. The sensor sends a signal to the A/C amplifier assembly via the hybrid vehicle control ECU. The resistance of the A/C 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 hybrid vehicle control ECU applies voltage (5 V) to the A/C ambient temperature sensor and reads voltage changes as the resistance of the A/C ambient temperature sensor changes. The hybrid vehicle control ECU sends the read signal to the A/C amplifier via CAN and body multiplex communications.






WIRING DIAGRAM





INSPECTION PROCEDURE

PROCEDURE

1. READ VALUE OF TECHSTREAM
(a) Connect the Techstream to the DLC3.
(b) Turn the ignition switch ON and push the Techstream main switch on.
(c) Select the item below in the DATA LIST, and read the display on the Techstream.

Air Conditioner





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






C -- REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY
B -- PROCEED TO NEXT CIRCUIT INSPECTION SHOWN IN PROBLEM SYMPTOMS TABLE
A -- Continue to next step.
2. INSPECT HYBRID VEHICLE CONTROL ECU





(a) Remove the hybrid vehicle control ECU with the connectors still connected.
(b) Measure the voltage according to the value(s) in the table below.
Voltage:





HINT: As the temperature increases, the voltage decreases.

Result:






C -- REPLACE HYBRID VEHICLE CONTROL ECU
B -- PROCEED TO NEXT CIRCUIT INSPECTION SHOWN IN PROBLEM SYMPTOMS TABLE
A -- Continue to next step.
3. INSPECT A/C AMBIENT TEMPERATURE SENSOR





(a) Remove the A/C ambient temperature sensor.
(b) Disconnect the connector from the A/C ambient temperature sensor.
(c) Measure the resistance according to the value(s) in the table below.





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 A/C AMBIENT TEMPERATURE SENSOR
OK -- Continue to next step.
4. CHECK HARNESS AND CONNECTOR (A/C AMBIENT TEMPERATURE SENSOR - HYBRID VEHICLE CONTROL ECU)





(a) Disconnect the connector from the hybrid vehicle control ECU.
(b) Measure the resistance according to the value(s) in the table below.
Resistance:






NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- REPLACE HYBRID VEHICLE CONTROL ECU