- Thermistor assembly (ambient temperature sensor)
- Harness or connector between thermistor assembly (ambient temperature sensor) and air conditioning amplifier
- Air conditioning amplifier
| Last Modified: 11-29-2007 | 1.6 C | |
| Service Category: Vehicle Interior | Section: Heating/Air Conditioning | |
| Model Year: 2008 | Model: Sequoia | Doc ID: RM000002VXC004X |
| Title: HEATING / AIR CONDITIONING: AIR CONDITIONING SYSTEM: DESCRIPTION (2008 Sequoia) | ||
|
DTC |
B1412/12 |
Ambient Temperature Sensor Circuit |
DESCRIPTION
The thermistor assembly (ambient temperature sensor) is installed in front of the condenser to detect the ambient temperature which is used to control the air conditioner "AUTO" mode. This sensor is connected to the air conditioning amplifier 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. The resistance of the thermistor assembly (ambient temperature sensor) changes in accordance with the ambient temperature. As the temperature decreases, the resistance increases. As the temperature increases, the resistance decreases.
The air conditioning amplifier applies voltage (5 V) to the thermistor assembly (ambient temperature sensor) and reads voltage changes as the resistance of the thermistor assembly (ambient temperature sensor) changes.
|
DTC Code |
DTC Detection Condition |
Trouble Area |
|---|---|---|
|
B1412/12 |
Open or short in ambient temperature sensor circuit |
|
WIRING DIAGRAM
INSPECTION PROCEDURE
PROCEDURE
|
1. |
READ VALUE USING TECHSTREAM (AMBIENT TEMPERATURE SENSOR) |
(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 / Ambient Temp Sensor.
(e) According to the display on the Techstream, read the Data List.
Air Conditioner
|
Tester Display |
Measurement Item/Range |
Normal Condition |
Diagnostic Note |
|---|---|---|---|
|
Ambient Temp Sensor |
Ambient temperature sensor / Min.: -23.3°C (-9.94°F) Max.: 65.95°C (150.71°F) |
Actual ambient temperature is displayed |
Open in circuit: -23.3°C (-9.94°F) Short in circuit: 65.95°C (150.71°F) |
OK:
The display is as specified in the normal condition.
Result
|
Result |
Proceed to |
|---|---|
|
NG |
A |
|
OK (When troubleshooting according to Problem Symptoms Table) |
B |
|
OK (When troubleshooting according to the DTC output) |
C |
|
|
4. |
INSPECT THERMISTOR ASSEMBLY (AMBIENT TEMPERATURE SENSOR) |
|
(a) Remove the thermistor assembly (ambient temperature sensor)
|
(b) Measure the resistance according to the value(s) in the table below.
Standard Resistance:
|
Tester Connection |
Condition |
Specified Condition |
|---|---|---|
|
1 - 2 |
10°C (50°F) |
3.00 to 3.73 kΩ |
|
15°C (59°F) |
2.45 to 2.88 kΩ |
|
|
20°C (68°F) |
1.95 to 2.30 kΩ |
|
|
25°C (77°F) |
1.60 to 1.80 kΩ |
|
|
30°C (86°F) |
1.28 to 1.47 kΩ |
|
|
35°C (95°F) |
1.00 to 1.22 kΩ |
|
|
40°C (104°F) |
0.80 to 1.00 kΩ |
|
|
45°C (113°F) |
0.65 to 0.85 kΩ |
|
|
50°C (122°F) |
0.50 to 0.70 kΩ |
|
|
55°C (131°F) |
0.44 to 0.60 kΩ |
|
|
60°C (140°F) |
0.36 to 0.50 kΩ |
HINT:
- Even slightly touching the sensor may change the resistance value. Be sure to hold the connector of the sensor.
- When measuring, the sensor temperature must be the same as the ambient temperature.
- As the temperature increases, the resistance decreases (see the graph).
(c) Reinstall the thermistor assembly (ambient temperature sensor).
|
|
6. |
CHECK HARNESS AND CONNECTOR (AMBIENT TEMPERATURE SENSOR - AIR CONDITIONING AMPLIFIER) |
|
(a) Disconnect the A18 thermistor assembly (ambient temperature sensor) connector. |
(b) Disconnect the H24 air conditioning amplifier connector.
(c) Measure the resistance according to the value(s) in the table below.
Standard Resistance:
|
Tester Connection |
Condition |
Specified Condition |
|---|---|---|
|
A18-1 - H24-5 (TAM) |
Always |
Below 1 Ω |
|
A18-2 - H24-13 (SG-2) |
Always |
Below 1 Ω |
|
A18-1 or H24-5 (TAM) - Body ground |
Always |
10 kΩ or higher |
|
A18-2 or H24-13 (SG-2) - Body ground |
Always |
10 kΩ or higher |
(d) Reconnect the air conditioning amplifier connector.
(e) Reconnect the thermistor assembly (ambient temperature sensor) connector.
|
|
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