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. |
Diagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
Ambient Air Temperature Sensor Signal | B0158 02 | B0158 05 | B0158 05 | 1 |
Upper Air Temperature Sensor Signal | B0173 06 | B0173 05 | B0173 05 | 1 |
Lower Air Temperature Sensor Signal | B0178 06 | B0178 05 | B0178 05 | 1 |
Sunload Sensor Signal | B0183 02 | B0183 05 | B0183 05 | 1 |
Ambient Air Temperature Sensor Low Reference | -- | B0158 05 | -- | -- |
Upper Air Temperature Sensor Low Reference | -- | B0173 05 | -- | -- |
Lower Air Temperature Sensor Low Reference | -- | B0178 05 | -- | -- |
Sunload Sensor Low Reference | -- | B0183 05 | -- | -- |
Sunload Sensor Ground | -- | B0183 05 | -- | -- |
1. Air Temperature Malfunction | ||||
Circuit/System Description
Air Temperature Sensors
The air temperature sensors are a 2-wire negative temperature co-efficient thermistor. The vehicle uses the following air temperature sensors:
| • | Ambient air temperature sensor |
| • | Upper air temperature sensor |
| • | Lower air temperature sensor |
A signal and low reference circuit enables the sensor to operate. As the air temperature surrounding the sensor increases, the sensor resistance decreases. The sensor signal voltage decreases as the resistance decreases. The sensor operates within a temperature range between -40 to +101°C (-40 to +215°F). The sensor signal varies between 0-5 volts. The input of the duct air temperature sensors are different from the ambient and inside air temperature sensors. The HVAC control module converts the signal to a range between 0-255 counts. As the air temperature increases the count value will decrease.
Sun Load Sensor Assembly
The sunload sensor is a 2-wire photo diode. The vehicle uses a single sunload sensor. The sensor is integrated into the sunload sensor assembly along with the ambient light sensor. Body ground and signal circuits enable the sensor to operate. As the sunload increases, the sensor signal decreases. The sensor operates within an intensity range between completely dark and very bright. The sensor signal varies between 0-5 volts. The body control module (BCM) converts the signal to a range between 0-255 counts. The sunload sensor provides the HVAC control module with a measurement of the amount of light shining on the vehicle. Bright or high intensity light causes the vehicles interior temperature to increase. The HVAC system compensates for the increased temperature by diverting additional cool air into the vehicle.
Diagnostic Aids
Condition | Display |
|---|---|
Using Scan Tool Special Function | Updates temperature display instantly |
When the HVAC module A/C and RECIRCULATION buttons are pressed simultaneously | Updates temperature display instantly |
At start up with the engine off less than 2 hours | Displays last stored temperature unless temperature has decreased. The outside air temperature reading is always instantly updated if ambient air temperature has decreased. |
At start up with the engine off more than 2 hours | Displays actual outside temperature |
Vehicle speed above 32 km/h (20 mph) for a minimum of 80 seconds | Updates temperature display at a slow filtered rate |
Vehicle speed above 72 km/h (45 mph) | Displays actual outside temperature |
Sensor ambient temperature reading is less than the last displayed value | Displays actual outside temperature |
When the ambient air decreases | Updates temperature display rapidly |
Reference Information
Schematic Reference
Connector End View Reference
Description and Operation
Electrical Information Reference
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Verification
- Ignition ON, cover the sunload sensor assembly with a shop towel or other suitable item. Verify the scan tool Right Sunload Sensor and Left Sunload Sensor parameters are within 3 counts of each other.
- Measure actual outside air temperature using a thermometer. Compare this value to the scan tool Ambient Air Temp Sensor parameter. The measured temperature should be within 5 degrees of parameter.
- Measure actual temperature using a thermometer at each of the duct temperature sensors. Compare this value to the appropriate scan tool Duct Actual parameter. The measured temperature should be within 5 degrees of appropriate Duct Actual parameter.
| ⇒ | If not within the specified range, refer to Sun Load Sensor Circuit Malfunction. |
| ⇒ | If not within the specified range, refer to Ambient Air Temperature Sensor Circuit Malfunction. |
| ⇒ | If not within the specified range, refer to Duct Temperature Sensor Circuit Malfunction. |
Circuit/System Testing
Sun Load Sensor Circuit Malfunction
- Ignition OFF, disconnect the harness connector at the sunload sensor.
- Test for less than 10 ohms between the ground circuit terminal C and ground.
- Ignition ON, test for 4.8-5.2 volts between the ground circuit terminal C and the appropriate signal circuit terminal A.
- If all circuits test normal, test or replace the sunload sensor.
| ⇒ | If greater than the specified range, test the ground circuit for an open/high resistance. |
| ⇒ | If less than the specified range, test the signal circuit for a short to ground or open/high resistance. If the circuit tests normal, replace the HVAC control module. |
| ⇒ | If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the HVAC control module. |
Ambient Air Temperature Sensor Circuit Malfunction
- Ignition OFF, disconnect the harness connector at the ambient temperature sensor.
- Test for less than 1 ohm between the low reference circuit terminal B and ground.
- Ignition ON, verify the appropriate scan tool Ambient Air Temp Sensor Voltage parameter is greater than 4.9 volts or 250 counts.
- Install a 3-amp fused jumper wire between the signal circuit terminal A and the low reference circuit terminal B. Verify the scan tool Temp Sensor Voltage parameter is less than 0.1 volt or 5 counts.
- If all circuits test normal, test or replace the appropriate temp sensor.
| ⇒ | If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the BCM. |
| ⇒ | If less than the specified range, test the signal circuit terminal A for a short to ground. If the circuit tests normal, replace the BCM. |
| ⇒ | If greater than the specified range, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM. |
Duct Temperature Sensor Circuit Malfunction
- Ignition OFF, disconnect the harness connector at the appropriate air duct temperature sensor.
- Ignition OFF, test for less than 10 ohms between the low reference circuit terminal B and ground.
- Ignition ON, verify that both the appropriate scan tool Duct Air Temp. Sensor parameter is less than 5 counts.
- Install a 3A fused jumper wire between the signal circuit terminal A and the low reference circuit terminal B. Verify the appropriate scan tool Duct Air Temp. Sensor parameter is greater than 250 counts.
- If all circuits test normal, test or replace the appropriate 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 HVAC control module. |
| ⇒ | If greater than the specified range, test the signal circuit terminal A for a short to ground. If the circuit tests normal, replace the HVAC control module. |
| ⇒ | If less than the specified range, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the HVAC control module. |
Component Testing
- A thermometer can be used to test the sensor off the vehicle in warm and or cold water. Refer to Sensor Resistance Table for this test.
- Test the appropriate temperature sensor by varying the sensor temperature in water while monitoring the sensor resistance.
- Compare the readings with the Temperature VS Resistance table and verify that the resistance is within 5 percent of the specification.
| ⇒ | If not within the specified range, replace the sensor. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for BCM and HVAC control module replacement, setup, and programming |
