Toyota CH-R Service Manual: Ambient Temperature Sensor Circuit (B1412)

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 combination meter assembly and detects fluctuations in the ambient temperature. This data is used for controlling the cabin temperature. The sensor sends a signal to the combination meter 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 combination meter assembly applies a 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	When the air conditioning amplifier assembly cannot receive outside temperature sensor data from the combination meter assembly.	Thermistor assembly Harness or connector between thermistor assembly and combination meter assembly Air conditioning amplifier assembly Combination meter assembly CAN communication system	Memorized (4 seconds or more)*

HINT:

If the ambient temperature is approximately -52.9°C (-63.22°F) or lower, DTC B1412/12 may be output even though the system is normal.

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

When replacing the combination meter assembly, always replace it with a new one. If a combination meter assembly which was installed to another vehicle is used, the information stored in it will not match the information from the vehicle and a DTC may be stored.

PROCEDURE

1.	CHECK CAN COMMUNICATION SYSTEM

(a) Check if CAN communication DTCs are output.

Click here

Result	Proceed to
CAN communication DTCs are not output.	A
CAN communication DTCs are output.	B

B

GO TO CAN COMMUNICATION SYSTEM

A

2.	READ VALUE USING TECHSTREAM (AMBIENT TEMPERATURE)

(a) Connect the Techstream to the DLC3.

(b) Turn the ignition switch ON.

(c) Turn the Techstream on.

(d) Enter the following menus: Body Electrical / Combination Meter / Data List.

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

Body Electrical > Combination Meter > Data List

Tester Display	Measurement Item	Range	Normal Condition	Diagnostic Note
Ambient Temperature	Outside temperature	Min.: -40°C (-40°F) Max.: 87.5°C (189.5°F)	Almost the same as actual outside temperature	The temperature displayed on the multi information display is -40 to 50°C (-40 to 122°F)

Body Electrical > Combination Meter > Data List

Tester Display
Ambient Temperature

OK:

The display is as specified in the normal condition column.

Result	Proceed to
NG	A
OK (When troubleshooting according to Problem Symptoms Table)	B
OK (When troubleshooting according to the DTC)	C

B

PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE

C

GO TO STEP 5

A

3.	INSPECT THERMISTOR ASSEMBLY

(a) Remove the thermistor assembly.

Click here

(b) Inspect the thermistor assembly.

Click here

NG

REPLACE THERMISTOR ASSEMBLY

OK

4.	CHECK HARNESS AND CONNECTOR (THERMISTOR ASSEMBLY - COMBINATION METER ASSEMBLY)

(a) Disconnect the A3 thermistor assembly connector.

(b) Disconnect the F4 combination meter assembly connector.

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

Standard Resistance:

Tester Connection	Condition	Specified Condition
F4-34 (TEMP) - A3-2	Always	Below 1 Ω
F4-35 (TX1+) - A3-1	Always	Below 1 Ω
F4-34 (TEMP) or A3-2 - Body ground	Always	10 kΩ or higher
F4-35 (TX1+) or A3-1 - Body ground	Always	10 kΩ or higher

OK

REPLACE COMBINATION METER ASSEMBLY

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

5.	CHECK FOR DTC

(a) Clear the DTCs.

Click here

Body Electrical > Air Conditioner > Clear DTCs

(b) Check for DTCs.

Click here

Body Electrical > Air Conditioner > Trouble Codes

Result	Proceed to
DTCs are not output	A
DTCs are output	B

A

USE SIMULATION METHOD TO CHECK

B

REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY