Lexus NX: Ambient Temperature Sensor Circuit (B1412)

DESCRIPTION

The thermistor assembly (ambient temperature sensor) is installed in front of the cooler condenser assembly to detect the ambient temperature which is used to control the air conditioning system AUTO mode. This sensor is connected to the air conditioning amplifier assembly and detects fluctuations in the ambient temperature. This data is used for controlling the cabin temperature. The sensor sends a signal to the air conditioning amplifier assembly. The resistance of the thermistor assembly (ambient temperature sensor) changes in accordance with the ambient temperature. As the temperature decreases, the resistance increases. Conversely, as the temperature increases, the resistance decreases.

The air conditioning amplifier assembly applies a voltage (5 V) to the thermistor assembly (ambient temperature sensor) and reads voltage changes due to changes in the resistance of the thermistor assembly (ambient temperature sensor).

DTC No.

Detection Item

DTC Detection Condition

Trouble Area

Memory

Note

B1412

Ambient Temperature Sensor Circuit

  • Diagnosis condition: None
  • Malfunction state: Open or short in thermistor assembly (ambient temperature sensor) circuit
  • Malfunction Period: None (as present malfunction), memorized (4 seconds or more) (as past malfunction)
  • Thermistor assembly (ambient temperature sensor)
  • Harness and connector
  • Air conditioning amplifier assembly

Memorized (4 seconds or more)

-

HINT:

  • The air conditioning amplifier assembly stores the DTC of the respective malfunction if it has occurred for the period of time indicated in the brackets.
  • If the ambient temperature is approximately -52.9°C (-63.22°F) or less, DTC B1412 may be output even though the system is normal.

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

  • When the auxiliary battery terminal is disconnected or the air conditioning amplifier assembly is replaced, be sure to perform servo motor initialization.

    Click here

  • The air conditioning system uses the CAN communication system. Inspect the communication function by following How to Proceed with Troubleshooting. Troubleshoot the air conditioning system after confirming that the communication system is functioning properly.

    Click here

PROCEDURE

1.

READ VALUE USING TECHSTREAM

(a) Connect the Techstream to the DLC3.

(b) Turn the power switch on (IG).

(c) Turn the Techstream on.

(d) Enter the following menus: Body Electrical / Air Conditioner / Data List.

(e) Check the value(s) by referring to the table below.

Body Electrical > Air Conditioner > Data List

Tester Display

Measurement Item

Range

Normal Condition

Diagnostic Note

Ambient Temp Sensor

Thermistor assembly (ambient temperature sensor)

Min.: -23.30°C (-9.94°F)

Max.: 65.95°C (150.71°F)

Actual ambient temperature displayed

  • Thermistor assembly (ambient temperature sensor) system malfunction:
    • When open circuit: -23.30°C
    • When short circuit: 65.95°C
Body Electrical > Air Conditioner > Data List

Tester Display

Ambient Temp Sensor

OK:

The display is as specified in the normal condition column.

Result

Proceed to

OK (When troubleshooting according to Problem Symptoms Table)

A

OK (When troubleshooting according to the DTC)

B

NG

C

A

PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE

B

INSPECT AIR CONDITIONING AMPLIFIER ASSEMBLY

C

2.

INSPECT THERMISTOR ASSEMBLY (AMBIENT TEMPERATURE SENSOR)

(a) Remove the thermistor assembly (ambient temperature sensor).

Click here

(b) Inspect the thermistor assembly (ambient temperature sensor).

Click here

NG

REPLACE THERMISTOR ASSEMBLY (AMBIENT TEMPERATURE SENSOR)

OK

3.

CHECK HARNESS AND CONNECTOR (THERMISTOR ASSEMBLY [AMBIENT TEMPERATURE SENSOR] - AIR CONDITIONING AMPLIFIER ASSEMBLY)

(a) Disconnect the A16 thermistor assembly (ambient temperature sensor) connector.

(b) Disconnect the I50 air conditioning amplifier assembly connector.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

A16-2 - I50-5 (TAM)

Always

Below 1 Ω

A16-1 - I50-13 (SG-2)

Always

Below 1 Ω

A16-1 - A16-2

Always

10 kΩ or higher

A16-2 or I50-5 (TAM) - Body ground

Always

10 kΩ or higher

A16-1 or I50-13 (SG-2) - Body ground

Always

10 kΩ or higher

OK

INSPECT AIR CONDITIONING AMPLIFIER ASSEMBLY

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

READ NEXT:

 Evaporator Temperature Circuit or Evaporator Fin Thermistor (B1413)

DESCRIPTION The No. 1 cooler thermistor (evaporator temperature sensor) is installed on the evaporator in the air conditioner unit to detect the temperature of the air that has passed through the evap

 Open in Pressure Sensor Circuit / Abnormal Refrigerant Pressure (B1423)

DESCRIPTION This DTC is stored if refrigerant pressure on the high pressure side is extremely low (176 kPa (1.8 kgf/cm2, 26 psi) or less) or extremely high (3025 kPa (30.8 kgf/cm2, 439 psi) or more).

 Air Mix Damper Control Servo Motor Circuit (Passenger Side) (B1441)

DESCRIPTION The No. 1 air conditioning radiator damper servo sub-assembly (front passenger side air mix) sends pulse signals to indicate the damper position to the air conditioning amplifier assembly.

SEE MORE:

 Vehicle Speed Sensor Malfunction (B2415)

DESCRIPTION The headlight ECU sub-assembly LH receives speed signals from the brake booster with master cylinder assembly (skid control ECU) via CAN communication and performs light control. DTC No. Detection Item DTC Detection Condition Trouble Area B2415 Vehicle Speed Sensor Malfunc

 Power Source Voltage Malfunction (C1782)

DESCRIPTION DTC No. Detection Item DTC Detection Condition Trouble Area Warning Indicate C1782 Power Source Voltage Malfunction While the power switch is on (IG), the voltage at terminal B is 10 V or less, or 16 V or higher for 0.5 seconds. AVS fuse Auxiliary battery Char

© 2016-2024 Copyright www.lexunx.com