Lexus NX: 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 heater and air conditioning system AUTO mode. 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 a voltage (5 V) to the cooler thermistor (room temperature sensor) 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 | Note |
|---|---|---|---|---|---|
| B1411 | Room Temperature Sensor Circuit | Open or short in cooler thermistor (room temperature sensor) circuit |
| 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 cabin temperature is approximately -18.6°C (-1.48°F) or less, DTC B1411 may be output even though the system is normal.
WIRING DIAGRAM
CAUTION / NOTICE / HINT
NOTICE:
When the auxiliary battery is disconnected or the air conditioning amplifier assembly is replaced, be sure to perform servo motor initialization.
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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 |
|---|---|---|---|---|
| Room Temperature Sensor | Cooler thermistor (room temperature sensor) | Min.: -6.50°C (-20.30°F) Max.: 57.25°C (135.05°F) | Actual ambient temperature displayed | - |
| Tester Display |
|---|
| Room Temperature 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 | .gif) | PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE |
| B | | REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY |
|
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| 2. | INSPECT COOLER THERMISTOR (ROOM TEMPERATURE SENSOR) |
(a) Remove the cooler thermistor (room temperature sensor).
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(b) Inspect the cooler thermistor (room temperature sensor).
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| NG | | REPLACE COOLER THERMISTOR (ROOM TEMPERATURE SENSOR) |
|
| 3. | CHECK HARNESS AND CONNECTOR (AIR CONDITIONING AMPLIFIER ASSEMBLY - COOLER THERMISTOR [ROOM TEMPERATURE SENSOR]) |
(a) Disconnect the I50 air conditioning amplifier assembly connector.
(b) Disconnect the I12 cooler thermistor (room temperature sensor) connector.
(c) Measure the resistance according to the value(s) in the table below.
Standard Resistance:
| Tester Connection | Condition | Specified Condition |
|---|---|---|
| I50-29 (TR) - I12-1 | Always | Below 1 Ω |
| I50-34 (SG-1) - I12-2 | Always | Below 1 Ω |
| I50-29 (TR) or I12-1 - Body ground | Always | 10 kΩ or higher |
| I50-34 (SG-1) or I12-2 - Body ground | Always | 10 kΩ or higher |
| OK | | REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY |
| NG | | REPAIR OR REPLACE HARNESS OR CONNECTOR |
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