Lexus IS250 · Service Manual HEATER & AIR CONDITIONING SYSTEM

B1412/12

Diagnostic trouble codes

DESCRIPTION

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 connected to the ECM 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 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 signal to the A/C amplifier via CAN and body multiplex communication.
DTC No.
 DTC Detection Condition
 Trouble Area
B1412/12
 Open or short in ambient temperature sensor circuit
  1. Ambient temperature sensor
  2. Harness and connector between ambient temperature sensor and ECM
  3. ECM
  4. Multiplex communication circuit
  5. A/C amplifier

WIRING DIAGRAM

E110807E01

INSPECTION PROCEDURE

4GR-FSE:

1. CHECK MULTIPLEX COMMUNICATION SYSTEM

  1. Use the intelligent tester to check if the Multiplex Communication System (MPX) is functioning normally.

Result:
Result
 Proceed to
MPX DTC is not output
 A
MPX DTC is output
 B



B
GO TO MULTIPLEX COMMUNICATION SYSTEM
A


2. CHECK CAN COMMUNICATION SYSTEM

  1. Use the intelligent tester to check if the CAN Communication System is functioning normally.

    Result:
    Result
    		 Proceed to
    CAN DTC is not output
    		 A
    CAN DTC is output
    		 B



B
GO TO CAN COMMUNICATION SYSTEM
A


3. READ VALUE OF INTELLIGENT TESTER

  1. Connect the intelligent tester to the DLC3.

  1. Turn the engine switch on (IG) and turn the intelligent tester main switch on.

  1. Select the item below in the Data List, and read the display on the intelligent tester.

Data List / Air Conditioner: 
Item
 Measurement Item / Display (Range)
 Normal Condition
 Diagnostic Note
Ambient Temp Sensor
(Ambi Temp Sens)
 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 the PROBLEM SYMPTOMS TABLE)
 B
OK (When troubleshooting according to the DTC)
 C



B
PROCEED TO NEXT CIRCUIT INSPECTION SHOWN IN PROBLEM SYMPTOMS TABLE

C
REPLACE AIR CONDITIONING AMPLIFIER
A


4. INSPECT AMBIENT TEMPERATURE SENSOR

  1. E118395E02
    Remove the ambient temperature sensor.

  1. Measure the resistance according to the value(s) in the table below.

    Standard resistance:
    Tester Connection
    		 Condition
    		 Specified Condition
    B5-1 - B5-2
    		 10°C (50°F)
    		 3.00 to 3.73 kΩ
    B5-1 - B5-2
    		 15°C (59°F)
    		 2.45 to 2.88 kΩ
    B5-1 - B5-2
    		 20°C (68°F)
    		 1.95 to 2.30 kΩ
    B5-1 - B5-2
    		 25°C (77°F)
    		 1.60 to 1.80 kΩ
    B5-1 - B5-2
    		 30°C (86°F)
    		 1.28 to 1.47 kΩ
    B5-1 - B5-2
    		 35°C (95°F)
    		 1.00 to 1.22 kΩ
    B5-1 - B5-2
    		 40°C (104°F)
    		 0.80 to 1.00 kΩ
    B5-1 - B5-2
    		 45°C (113°F)
    		 0.65 to 0.85 kΩ
    B5-1 - B5-2
    		 50°C (122°F)
    		 0.50 to 0.70 kΩ
    B5-1 - B5-2
    		 55°C (131°F)
    		 0.44 to 0.60 kΩ
    B5-1 - B5-2
    		 60°C (140°F)
    		 0.36 to 0.50 kΩ

    NOTICE:
    1. Even slightly touching the sensor may change the resistance value. Be sure to hold the connector of the sensor.
    2. 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


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

  1. E118396E02
    Disconnect the ambient temperature sensor connector.

  1. Disconnect the ECM connectors.

  1. Measure the resistance according to the value(s) in the table below.

    Standard resistance:
    Tester Connection
    		 Condition
    		 Specified Condition
    B5-1 - A5-18 (TAM)
    		 Always
    		 Below 1 Ω
    B5-2 - E5-30 (E3)
    		 Always
    		 Below 1 Ω
    A5-18 (TAM) - Body ground
    		 Always
    		 10 kΩ or higher
    E5-30 (E3) - Body ground
    		 Always
    		 10 kΩ or higher



NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

REPLACE ECM


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