Lexus NX: Ambient Temperature Sensor Circuit (B1412)
DESCRIPTION
The thermistor assembly (ambient temperature sensor) is installed in front of the cooler condenser assembly to detect the ambient temperature which is used to control the air conditioning system AUTO mode. 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 (ambient temperature sensor) changes in accordance with the ambient temperature. As the temperature decreases, the resistance increases. Conversely, as the temperature increases, the resistance decreases.
The air conditioning amplifier assembly applies a voltage (5 V) to the thermistor assembly (ambient temperature sensor) and reads voltage changes due to changes in the resistance of the thermistor assembly (ambient temperature sensor).
| DTC No. | Detection Item | DTC Detection Condition | Trouble Area | Memory | Note |
|---|---|---|---|---|---|
| B1412 | Ambient 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 ambient temperature is approximately -52.9°C (-63.22°F) or less, DTC B1412 may be output even though the system is normal.
WIRING DIAGRAM
CAUTION / NOTICE / HINT
NOTICE:
-
When the auxiliary battery terminal is disconnected or the air conditioning amplifier assembly is replaced, be sure to perform servo motor initialization.
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-
The air conditioning system uses the CAN communication system. Inspect the communication function by following How to Proceed with Troubleshooting. Troubleshoot the air conditioning system after confirming that the communication system is functioning properly.
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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 |
|---|---|---|---|---|
| Ambient Temp Sensor | Thermistor assembly (ambient temperature sensor) | Min.: -23.30°C (-9.94°F) Max.: 65.95°C (150.71°F) | Actual ambient temperature displayed |
|
| Tester Display |
|---|
| Ambient Temp 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 | | INSPECT AIR CONDITIONING AMPLIFIER ASSEMBLY |
|
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| 2. | INSPECT THERMISTOR ASSEMBLY (AMBIENT TEMPERATURE SENSOR) |
(a) Remove the thermistor assembly (ambient temperature sensor).
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(b) Inspect the thermistor assembly (ambient temperature sensor).
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| NG | | REPLACE THERMISTOR ASSEMBLY (AMBIENT TEMPERATURE SENSOR) |
|
| 3. | CHECK HARNESS AND CONNECTOR (THERMISTOR ASSEMBLY [AMBIENT TEMPERATURE SENSOR] - AIR CONDITIONING AMPLIFIER ASSEMBLY) |
(a) Disconnect the A16 thermistor assembly (ambient temperature sensor) connector.
(b) Disconnect the I50 air conditioning amplifier assembly connector.
(c) Measure the resistance according to the value(s) in the table below.
Standard Resistance:
| Tester Connection | Condition | Specified Condition |
|---|---|---|
| A16-2 - I50-5 (TAM) | Always | Below 1 Ω |
| A16-1 - I50-13 (SG-2) | Always | Below 1 Ω |
| A16-1 - A16-2 | Always | 10 kΩ or higher |
| A16-2 or I50-5 (TAM) - Body ground | Always | 10 kΩ or higher |
| A16-1 or I50-13 (SG-2) - Body ground | Always | 10 kΩ or higher |
| OK | | INSPECT AIR CONDITIONING AMPLIFIER ASSEMBLY |
| NG | | REPAIR OR REPLACE HARNESS OR CONNECTOR |
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