Lexus RX (RX 350L, RX450h) 2016-2025 Repair Manual: Rear Room Temperature Sensor Circuit (B1419/19)

Lexus RX (RX 350L, RX450h) 2016-2025 Repair Manual / Vehicle Interior / Heating / Air Conditioning / Air Conditioning System / Rear Room Temperature Sensor Circuit (B1419/19)

DESCRIPTION

The cooler (No. 2 room temp. sensor) thermistor is installed in the rear panel to detect the rear cabin temperature, which is used to control the air conditioning system. The resistance of the cooler (No. 2 room temp. sensor) thermistor changes in accordance with the rear 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 (No. 2 room temp. sensor) thermistor and reads voltage changes due to changes in the resistance of the cooler (No. 2 room temp. sensor) thermistor.

DTC No.

Detection Item

DTC Detection Condition

Trouble Area

Memory

B1419/19

Rear Room Temperature Sensor Circuit

Open or short in rear room temperature sensor circuit
  • Cooler (No. 2 room temp. sensor) thermistor
  • Harness or connector
  • Air conditioning amplifier assembly

Memorized

(4 sec. or more)*1
  • *1: The air conditioning amplifier assembly stores this DTC if the malfunction has occurred for the period of time indicated in the brackets.

WIRING DIAGRAM

PROCEDURE

1.

READ VALUE USING TECHSTREAM

(a) Connect the Techstream to the DLC3.

(b) Turn the engine 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

Room Temp Sensor (Rear)

Cooler (No. 2 room temp. sensor) thermistor

Min.: -6.50°C (20.30°F)

Max.: 57.25°C (135.05°F)

Actual rear cabin temperature displayed

-
Body Electrical > Air Conditioner > Data List

Tester Display

Room Temp Sensor (Rear)

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

REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY

C

2.

INSPECT COOLER (NO. 2 ROOM TEMP. SENSOR) THERMISTOR

(a) Remove the cooler (No. 2 room temp. sensor) thermistor.

Click here

(b) Inspect the cooler (No. 2 room temp. sensor) thermistor.

Click here

NG

REPLACE COOLER (NO. 2 ROOM TEMP. SENSOR) THERMISTOR

OK

3.

CHECK HARNESS AND CONNECTOR (COOLER (NO. 2 ROOM TEMP. SENSOR) THERMISTOR - AIR CONDITIONING AMPLIFIER ASSEMBLY)

(a) Disconnect the J48 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

S87-1 (+) - J48-6 (TR)

Always

Below 1 Ω

S87-2 (-) - J48-20 (SG-7)

Always

Below 1 Ω

S87-1 (+) or J48-6 (TR) - Other terminals and body ground

Always

10 kΩ or higher

S87-2 (-) or J48-20 (SG-7) - Other terminals and body ground

Always

10 kΩ or higher
OK

REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR
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