Toyota CH-R Service Manual: Room Temperature Sensor Circuit (B1411)

DESCRIPTION

The cooler thermistor (room temperature sensor) is installed in the instrument panel to detect the cabin temperature, which is used to control the air conditioning system. The resistance of the cooler thermistor (room temperature sensor) changes in accordance with the cabin 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 cooler thermistor (room temperature sensor) thermistor and reads voltage changes due to changes in the resistance of the cooler thermistor (room temperature sensor).

DTC No.	Detection Item	DTC Detection Condition	Trouble Area	Memory
B1411	Room Temperature Sensor Circuit	Any of the following conditions is met: Open in cooler thermistor (room temperature sensor) circuit Short in cooler thermistor (room temperature sensor) circuit	Cooler thermistor (room temperature sensor) Harness or connector between cooler thermistor (room temperature sensor) and air conditioning amplifier assembly Air conditioning amplifier assembly	Memorized (4 seconds or more)*

HINT:

If the cabin temperature is approximately -18.6°C (-1.48°F) or lower, DTC B1411 may be output even though the system is normal.

DTC Detection Conditions

		Vehicle Condition
		Pattern 1	Pattern 2
Diagnosis Condition	Ignition switch ON	○	○
Malfunction Status	Open in cooler thermistor (room temperature sensor) circuit	○	-
	Short in cooler thermistor (room temperature sensor) circuit	-	○
Detection Time		4 seconds or more	4 seconds or more
Number of Trips		1 trip	1 trip

HINT:

DTC will be output when conditions for either of the patterns in the table above are met.

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
Room Temperature Sensor	Cooler thermistor (room temperature sensor)	Min.: -6.50°C (20.30°F) Max.: 57.25°C (135.05°F)	Actual cabin temperature displayed	-

Body Electrical > Air Conditioner > Data List

Tester Display
Room Temperature Sensor

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 4

A

2.	INSPECT COOLER THERMISTOR (ROOM TEMPERATURE SENSOR)

(a) Remove the cooler thermistor (room temperature sensor).

Click here

(b) Inspect the cooler thermistor (room temperature sensor).

Click here

NG

REPLACE COOLER (ROOM TEMP. SENSOR) THERMISTOR

OK

3.	CHECK HARNESS AND CONNECTOR (COOLER THERMISTOR (ROOM TEMPERATURE SENSOR) - AIR CONDITIONING AMPLIFIER ASSEMBLY)

(a) Disconnect the F138 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
F138-14 (TR) - F60-1	Always	Below 1 Ω
F138-1 (SG-1) - F60-2	Always	Below 1 Ω
F138-14 (TR) or F60-1 - Body ground	Always	10 kΩ or higher
F138-1 (SG-1) or F60-2 - Body ground	Always	10 kΩ or higher

OK

REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

4.	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