Diagnostic Instructions
| • | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
| • | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
| • | Diagnostic Procedure Instructions provides an overview of each diagnostic category. |
Circuit/System Description
The inside rearview mirror (ISRVM) applies 5 volts to the ambient air temperature sensor. The ambient air temperature sensor is a thermistor which varies in resistance as the temperature changes. As the resistance of the ambient air temperature sensor increases, the ISRVM senses a larger voltage drop across the sensor, indicating a lower temperature. As the resistance of the ambient air temperature sensor decreases, the ISRVM senses a smaller voltage drop across the sensor, indicating a higher temperature.
Diagnostic Aids
The following table will be used to measure the resistance of the sensor and compare it with the actual ambient temperature. The mirror's temperature accuracy should be within 5 degrees of the actual temperature. The actual temperature should not be taken from a radio station, a sign displaying the temperature, etc. A temperature measuring tool such as a thermometer should be used. Some temperature measuring tools may be within 5 degrees of the actual temperature. Make sure to consult the manufacturer for the accuracy of the tool. This comparison can make the mirror seem off by 5-10 degrees of the actual temperature when it is not.
°C | °F | Minimum Resistance K Ohms | Maximum Resistance K Ohms |
|---|---|---|---|
-35 | -31 | 234.81 | 250.59 |
-30 | -22 | 171.69 | 182.31 |
-25 | -13 | 126.82 | 133.99 |
-20 | -4 | 94.63 | 99.49 |
-15 | 5 | 71.30 | 74.58 |
-10 | 14 | 54.21 | 56.43 |
-5 | 23 | 41.48 | 43.17 |
0 | 32 | 32.00 | 33.31 |
5 | 41 | 24.96 | 25.83 |
10 | 50 | 19.61 | 20.19 |
15 | 59 | 15.49 | 15.94 |
20 | 68 | 12.31 | 12.67 |
25 | 77 | 9.85 | 10.12 |
30 | 86 | 7.96 | 8.15 |
35 | 95 | 6.45 | 6.61 |
40 | 104 | 5.27 | 5.39 |
45 | 113 | 4.32 | 4.42 |
50 | 122 | 3.56 | 3.64 |
55 | 131 | 2.95 | 3.02 |
60 | 140 | 2.46 | 2.52 |
Reference Information
Schematic Reference
Inside Rearview Mirror Schematics
Connector End View Reference
Description and Operation
Automatic Day-Night Mirror Description and Operation
Electrical Information Reference
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Testing
- Ignition OFF, disconnect the ambient air temperature sensor.
- Ignition OFF, test for less than 1 ohm between the low reference circuit terminal B and ground.
- Ignition ON, verify that OC is displayed on the ISRVM display.
- Ignition ON, install a 3-amp fused jumper wire between the signal circuit terminal A and the low reference circuit terminal B. Verify that SC is displayed on the ISRVM display.
- If all circuits test normal, replace the ambient air temperature sensor.
| ⇒ | If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal replace the ISRVM. |
| ⇒ | If not the specified value, test the signal circuit terminal A for a short to ground. If the circuit tests normal replace the ISRVM. |
| ⇒ | If not the specified value, test the signal circuit for an open/high resistance. If the circuit tests normal replace the ISRVM. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for ISRVM replacement, setup, and programming |
