Last Modified: 05-13-2024 6.11:8.1.0 Doc ID: RM100000001H962
Model Year Start: 2020 Model: GR Corolla Prod Date Range: [01/2019 - 09/2022]
Title: HEATING / AIR CONDITIONING: AIR CONDITIONING SYSTEM (for Gasoline Model with Manual Air Conditioning System): B1412; Ambient Temperature Sensor Circuit; 2020 - 2022 MY Corolla Corolla Hatchback GR Corolla [01/2019 - 09/2022]

DTC

B1412

Ambient Temperature Sensor Circuit

DESCRIPTION

The thermistor assembly is installed in front of the cooler condenser assembly to detect the ambient temperature, which is used to control the air conditioning system. 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 changes in accordance with the ambient temperature. As the temperature decreases, the resistance increases. As the temperature increases, the resistance decreases.

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

DTC No.

Detection Item

DTC Detection Condition

Trouble Area

Memory

B1412

Ambient Temperature Sensor Circuit

Open or short in ambient temperature sensor circuit

  • Thermistor assembly
  • Harness or connector
  • Air conditioning amplifier assembly

Memorized

(4 sec. or more)*

  • *: The air conditioning amplifier assembly stores this DTC if the malfunction has occurred for the period of time indicated in the brackets.

HINT:

If the ambient temperature is approximately -52.9°C (-63.22°F) or lower, DTC B1412 may be stored even though the system is normal.

WIRING DIAGRAM

PROCEDURE

1.

READ VALUE USING TECHSTREAM

(a) Connect the Techstream to the DLC3.

(b) Turn the ignition switch to ON.

(c) Turn the Techstream on.

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

(e) Read the Data List according to the display on the Techstream.

Body Electrical > Air Conditioner > Data List

Tester Display

Measurement Item

Range

Normal Condition

Diagnostic Note

Ambient Temp Sensor

Thermistor assembly

Min.: -23.30°C (-9.94°F)

Max.: 65.95°C (150.71°F)

Actual ambient temperature displayed

Thermistor assembly circuit malfunction

  • When open circuit: -23.30°C (-9.94°F)
  • When short circuit: 65.95°C (150.71°F)

Body Electrical > Air Conditioner > Data List

Tester Display

Ambient Temp Sensor

OK:

The display is as specified in the normal condition column.

OK

REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY

NG

2.

INSPECT THERMISTOR ASSEMBLY

(a) Remove the thermistor assembly.

Click here 2020 - 2022 MY Corolla Corolla Hatchback Corolla HV [01/2019 - 09/2022]; HEATING / AIR CONDITIONING: AMBIENT TEMPERATURE SENSOR (except G16E-GTS): REMOVAL

(b) Inspect the thermistor assembly.

Click here 2019 - 2025 MY Corolla Corolla Hatchback Corolla HV [06/2018 -        ]; HEATING / AIR CONDITIONING: AMBIENT TEMPERATURE SENSOR (except G16E-GTS): INSPECTION

NG

REPLACE THERMISTOR ASSEMBLY

OK

3.

CHECK HARNESS AND CONNECTOR (THERMISTOR ASSEMBLY - AIR CONDITIONING AMPLIFIER ASSEMBLY)

(a) Disconnect the I48 air conditioning amplifier assembly connector.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

A3-1 - I48-1 (TAM)

Always

Below 1 Ω

A3-2 - I48-14 (SG-2)

Always

Below 1 Ω

A3-1 or I48-1 (TAM) - Other terminals and body ground

Always

10 kΩ or higher

A3-2 or I48-14 (SG-2) - Other terminals and body ground

Always

10 kΩ or higher

OK

REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR