RX400h · Service Manual HEATER & AIR CONDITIONING SYSTEM

B1412/12

Diagnostic trouble codes

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.
DTC No.
 DTC Detecting Condition
 Trouble Area
B1412/12
 Open or short in ambient temperature sensor circuit
  1. A/C ambient temperature sensor
  2. Harness or connector between A/C ambient temperature sensor and hybrid vehicle control ECU
  3. Hybrid vehicle control ECU
  4. Multiplex communication circuit
  5. A/C amplifier assembly

WIRING DIAGRAM

E109252E03

INSPECTION PROCEDURE


1. READ VALUE OF INTELLIGENT TESTER

  1. Connect the intelligent tester to the DLC3.

  1. Turn the ignition switch ON and push 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 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 the circuit: -23.3°C (-9.94°F)
Short in the circuit: 65.95°C (150.71°F)

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


Result:
Result
 Proceed to
NG
 A
OK (Checking from the PROBLEM SYMPTOMS TABLE)
 B
OK (Checking from the DTC)
 C



B
PROCEED TO NEXT CIRCUIT INSPECTION SHOWN IN PROBLEM SYMPTOMS TABLE

C
REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY
A


2. INSPECT HYBRID VEHICLE CONTROL ECU

  1. E108916E14
    Remove the hybrid vehicle control ECU with the connectors still connected.

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

    Voltage:
    Tester connection
    (Symbols)
    		 Condition
    		 Specified condition
    H31-19 (TAM) - H34-28 (E2)
    		 Ignition switch ON
    at 25°C (77°F)
    		 1.7 to 2.1 V
    H31-19 (TAM) - H34-28 (E2)
    		 Ignition switch ON
    at 40°C (104°F)
    		 1.0 to 1.4 V

    HINT:
    As the temperature increases, the voltage decreases.


Result:
Result
 Proceed to
NG
 A
OK (Checking from the PROBLEM SYMPTOMS TABLE)
 B
OK (Checking from the DTC)
 C



B
PROCEED TO NEXT CIRCUIT INSPECTION SHOWN IN PROBLEM SYMPTOMS TABLE

C
REPLACE HYBRID VEHICLE CONTROL ECU
A


3. INSPECT A/C AMBIENT TEMPERATURE SENSOR

  1. E108917E02
    Remove the A/C ambient temperature sensor.

  1. Disconnect the connector from the A/C ambient temperature sensor.

  1. Measure the resistance according to the value(s) in the table below.I040673E01

    Resistance:
    Tester connection
    		 Condition
    		 Specified condition
    A1-1 - A1-2
    		 10°C (50°F)
    		 3.00 to 3.73 kΩ
    A1-1 - A1-2
    		 15°C (59°F)
    		 2.45 to 2.88 kΩ
    A1-1 - A1-2
    		 20°C (68°F)
    		 1.95 to 2.30 kΩ
    A1-1 - A1-2
    		 25°C (77°F)
    		 1.60 to 1.80 kΩ
    A1-1 - A1-2
    		 30°C (86°F)
    		 1.28 to 1.47 kΩ
    A1-1 - A1-2
    		 35°C (95°F)
    		 1.00 to 1.22 kΩ
    A1-1 - A1-2
    		 40°C (104°F)
    		 0.80 to 1.00 kΩ
    A1-1 - A1-2
    		 45°C (113°F)
    		 0.65 to 0.85 kΩ
    A1-1 - A1-2
    		 50°C (122°F)
    		 0.50 to 0.70 kΩ
    A1-1 - A1-2
    		 55°C (131°F)
    		 0.44 to 0.60 kΩ
    A1-1 - A1-2
    		 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 A/C AMBIENT TEMPERATURE SENSOR
OK


4. CHECK HARNESS AND CONNECTOR (A/C AMBIENT TEMPERATURE SENSOR - HYBRID VEHICLE CONTROL ECU)

  1. E108902E06
    Disconnect the connector from the hybrid vehicle control ECU.

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

    Resistance:
    Tester connection
    		 Condition
    		 Specified condition
    H31-19 (TAM) - A1-2
    		 Always
    		 Below 1 Ω
    H34-28 (E2) - A1-1
    		 Always
    		 Below 1 Ω
    H31-19 (TAM) - Body ground
    		 Always
    		 10 kΩ or higher
    H34-28 (E2) - Body ground
    		 Always
    		 10 kΩ or higher



NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

REPLACE HYBRID VEHICLE CONTROL ECU


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