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Test Description

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The number(s) below refer to the step number(s) on the diagnostic table.

  1. 3:  Tests for the proper operation of the circuit in the high voltage range.
  2. 4:  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.
DTC B0174

Step Action Value(s) Yes No
Schematic Reference:  HVAC Schematics  
1 Did you perform the HVAC Diagnostic System Check? - Go to Step 2  Go to Diagnostic System Check - HVAC Systems - Automatic 
2
  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. With a scan tool, observe the Upper Outlet Temp. parameter in the Primary ECC Data list.
Does the scan tool indicate that the Upper Outlet Temp. parameter is within the specified range?		 5-250 Counts Go to Diagnostic Aids Go to Step 3 
3 
  1. Turn OFF the ignition.
  2. Disconnect the upper air temperature sensor.
  3. Turn ON the ignition, with the engine OFF.
  4. With a scan tool, observe the Upper Outlet Temp. parameter.
Does the scan tool indicate that the Upper Outlet Temp. parameter is greater than the specified value?		 250 Counts Go to Step 4  Go to Step 5 
4 
  1. Turn OFF the ignition.
  2. Connect a 3 amp fused jumper wire between the signal circuit of the upper air temperature sensor and the low reference circuit of the upper air temperature sensor.
  3. Turn ON the ignition, with the engine OFF.
  4. With a scan tool, observe the Upper Outlet Temp. parameter.
Does the scan tool indicate that the Upper Outlet Temp. parameter is less than the specified value?		 5 Counts Go to Step 8  Go to Step 6 
5 Test the signal circuit of the upper air temperature sensor for a short to ground. Refer to CIRCUIT TESTING and WIRING REPAIRS .
Did you find and correct the condition?		 - Go to Step 12  Go to Step 9 
6 Test the signal circuit of the upper air temperature sensor for a short to voltage, a high resistance, or an open. Refer to CIRCUIT TESTING and WIRING REPAIRS .
Did you find and correct the condition?		 - Go to Step 12  Go to Step 7 
7 Test the low reference circuit of the upper air temperature sensor for a high resistance or an open. Refer to CIRCUIT TESTING and WIRING REPAIRS .
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 upper air temperature sensor. Refer to TESTING FOR INTERMITTENT AND POOR CONNECTIONS and CONNECTOR REPAIRS .
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 HVAC control module. Refer to TESTING FOR INTERMITTENT AND POOR CONNECTIONS and CONNECTOR REPAIRS .
Did you find and correct the condition?		 - Go to Step 12  Go to Step 11 
10 Replace the upper air temperature sensor. Refer to Air Temperature Sensor Replacement - Upper .
Did you complete the replacement?		 - Go to Step 12  -
11
IMPORTANT: Perform the recalibration procedure for the HVAC control module.
Replace the HVAC control module. Refer to HVAC Control Module Replacement .Did you complete the replacement?		 - Go to Step 12  -
12
  1. Use the scan tool in order to clear the DTCs.
  2. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.
Does the DTC reset?		 - Go to Step 2  System OK
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