Circuit Description
The following DTCs are for the temperature sensors monitored by the instrument panel module (IPM):
| • | B0126 - Upper Right Air Temperature Sensor |
| • | B0131 - Lower Right Air Temperature Sensor |
| • | B0159 - Ambient Air Temperature Sensor |
| • | B0164 - Inside Air Temperature Sensor |
| • | B0174 - Upper Left Air Temperature Sensor |
| • | B0179 - Lower Left Air Temperature Sensor |
The IPM monitors the temperature sensors to maintain the comfort level inside of the vehicle. The temperature sensors are a 2 wire negative temperature co-efficient thermistor. The IPM applies 5 volts to internal input resistors that are connected to the signal circuits of the air temperature sensors. The IPM provides the ground to the air temperature sensors through the low reference circuit. The IPM monitors the voltage drop across the air temperature sensors and uses the inputs for automatic control calculations. When the air temperatures are cold, the resistance of the sensors are high and the voltage signals are high. When the air temperatures are hot, the resistance of the sensors are low and the voltage signals are low. The IPM converts the voltage values to count values where 1 volt is approximately equal to 51 counts.
DTC Descriptors
This diagnostic procedure supports the following DTCs:
| • | DTC B0126 Air Flow Position Command Circuit Range/Performance |
| • | DTC B0131 Air Flow Position Feedback Circuit Range/Performance |
| • | DTC B0159 Outside Air Temperature Sensor Circuit Range/Performance |
| • | DTC B0164 Passenger Compartment Temp Sensor Circuit Range/Performance |
| • | DTC B0174 Output Air Temperature Sensor Circuit Range/Performance |
| • | DTC B0179 Output Air Temperature Sensor 2 (lower or left) Circuit Range/Performance |
Conditions for Running the DTC
The ignition is turned ON.
Conditions for Setting the DTC
The IPM detects the sensor signal circuit is less than 0.09 volt (5 counts) or more than 4.90 volts (250 counts).
Conditions Taken When the DTC Sets
| • | Ambient air temperature sensor |
| - | A default value of 2.50 volts (128 counts) will be substituted for the ambient air temperature sensor data by the IPM. The Outside Air Temp displayed on the scan tool, 16°C (60°F) in the HVAC Sensor data list, will be the default value. The Outside Air Temp displayed on the scan tool in the Open/Short Data list will be the actual value. |
| - | The HVAC control module will display - - for ambient air temperature when OFF. |
| - | The HVAC control module will display the set temperature when ON. |
| • | Inside air temperature sensor |
| A default value of 2.5 volts (128 counts) will be substituted for the inside air temperature sensor data by the IPM. The Inside Air Temp displayed on the scan tool, 24°C (76°F) in the HVAC Sensor data list, will be the default value. The Inside Air Temp display on the scan tool in the Open/Short Data list will be the actual value. |
| • | HVAC duct temperature sensor |
| - | When the ambient air temperature is at or below 15°C (59°F), a default value of 4.80 volts (245 counts) will be substituted for the HVAC duct temperature sensor data by the IPM. The Duct Temp displayed on the scan tool, 31°C (88°F) in the HVAC Sensors data list, will be the default value. The Duct Temp displayed on the scan tool in the Open/Short Data list will be the actual value. |
| - | When the ambient air temperature is at or above 16°C (60°F), a default value of 0.19 volt (10 counts) will be substituted for the HVAC duct temperature sensor data by the IPM. The Duct Temp displayed on the scan tool, 119°C (246°F) in the HVAC Sensor data list, will be the default value. The Duct Temp displayed on the scan tool in the Open/Short Data list will be the actual value. |
Conditions for Clearing the DTC
| • | The DTC will become history if the IPM no longer detects a failure. |
| • | The history DTC will clear after 50 fault-free ignition cycles. |
| • | The DTC can be cleared by using a scan tool. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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The operating range of the sensor is between 0.09-4.90 volts. If the scan tool displays a value between 0-0.08 volt or 4.91-5.0 volts, then the sensor is performing outside of its designed limits.
-
Tests for the proper operation of the circuit in the high voltage range.
-
Tests for the proper operation of the circuit in the low voltage range. If the fuse in the jumper opens when you perform this test, the signal circuit is shorted to voltage.
-
Test the signal circuit for a short to ground.
-
Tests the signal circuit for a short to voltage, a high resistance, or an open.
-
Tests the low reference circuit for a high resistance or an open.
Step | Action | Values | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: HVAC Schematics Connector End View Reference: HVAC Connector End Views | ||||||||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information | ||||||
Does the scan tool indicate that the Temperature Sensor parameter is within the specified range? | 0.09-4.90 V | Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems | Go to Step 3 | |||||||
Does the scan tool indicate that the Temperature Sensor parameter is more than the specified value? | 4.90 V | Go to Step 4 | Go to Step 5 | |||||||
Does the scan tool indicate that the Temperature Sensor parameter is less than the specified value? | 0.09 V | Go to Step 8 | Go to Step 6 | |||||||
Test the appropriate signal circuit of the temperature sensor for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 9 | |||||||
Test the appropriate signal circuit of the temperature sensor for the following:
Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 7 | |||||||
Test the appropriate low reference circuit of the air temperature sensor for a high resistance or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 9 | |||||||
8 | Inspect for poor connections at the harness connector of the temperature sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 10 | ||||||
9 | Inspect for poor connections at the harness connector of the IPM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 11 | ||||||
10 | Replace the temperature sensor. Refer to the appropriate replacement procedure: Did you complete the replacement? | -- | Go to Step 12 | -- | ||||||
11 | Replace the IPM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 12 | -- | ||||||
12 |
Does the DTC reset? | -- | Go to Step 2 | System OK | ||||||
