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Home/Chevrolet/Silverado Classic 3500/Chevrolet Silverado Classic 3500 (2007-2007)/Repair manual/Automatic HVAC System/HVAC System - Automatic: Overview
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HVAC System - Automatic: Overview Chevrolet Silverado Classic 3500

Automatic HVAC System ~3068 words

Test Description

The number below refers to the step number on the diagnostic table.

  1. 2: This step verifies that the condition that set the DTC is present.
StepActionValuesYesNo
Schematic Reference: HVAC Schematics Connector End View Reference: HVAC Connector End Views
1Did you perform the Diagnostic System Check - Vehicle?Go to Step 2Go to Diagnostic System Check - Vehicle
2Install a scan tool. Turn ON the ignition, with the engine OFF. Select the HVAC control module display DTC function on the scan tool. Does the scan tool indicate that B0159 or B0164 is a current DTC?Go to Step 3Go to Testing for Intermittent Conditions and Poor Connections
3Turn OFF the ignition. Disconnect the appropriate air temperature sensor. Turn ON the ignition, with the engine OFF. Measure the voltage from the signal circuit of the appropriate air temperature sensor to a good ground. Does the voltage measure near the specified value?5 VGo to Step 4Go to Step 5
4Measure the voltage from the signal circuit to the low reference circuit of the appropriate air temperature sensor. Does the voltage measure near the specified value?5 VGo to Step 7Go to Step 6
5Test the signal circuit of the appropriate air temperature sensor for an open, high resistance, short to ground, or short to voltage. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition?Go to Step 11Go to Step 8
6Test the low reference circuit of the appropriate 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 11Go to Step 8
7Inspect for poor connections at the harness connector of the appropriate air temperature sensor assembly. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition?Go to Step 11Go to Step 9
8Inspect for poor connections at the harness connector of the HVAC control module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition?Go to Step 11Go to Step 10
9Replace the air temperature sensor assembly. Refer to the appropriate replacement procedure: Ambient Air Temperature Sensor Replacement Inside Air Temperature Sensor Assembly Replacement Did you complete the replacement?Go to Step 11
10Replace the HVAC control module. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement?Go to Step 11
11Use the scan tool in order to clear the DTCs. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text. Does the DTC reset?Go to Step 2System OK

DTC B0159 or B0164

The numbers below refer to the step numbers on the diagnostic table.

  1. 2: This step verifies that the temperature displayed is not within the calibrated range.
  2. 3: This step tests for the proper operation of the circuit in the high voltage range.
  3. 4: This step 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.
StepActionValue(s)YesNo
Schematic Reference: HVAC Schematics Connector End View Reference: HVAC Connector End Views
1Did you perform the Diagnostic System Check - Vehicle?Go to Step 2Go to Diagnostic System Check - Vehicle
2Install a scan tool. Turn ON the ignition, with the engine OFF. With a scan tool, observe the appropriate Duct Actual parameter in the Heating and Air Conditioning data list. Does the scan tool indicate that the Duct Actual parameter is within the specified range?5-250 CountsGo to Testing for Intermittent Conditions and Poor ConnectionsGo to Step 3
3Turn OFF the ignition. Disconnect the appropriate air temperature sensor. Turn ON the ignition, with the engine OFF. With a scan tool, observe the appropriate Duct Actual data parameter. Does the scan tool indicate that the Duct Actual data parameter is greater than the specified value?250 CountsGo to Step 4Go to Step 5
4Turn OFF the ignition. Connect a 3-amp fused jumper wire between the signal circuit of the air temperature sensor and the low reference circuit of the air temperature sensor. Turn ON the ignition, with the engine OFF. With a scan tool, observe the appropriate Duct Actual data parameter. Does the scan tool indicate that the Duct Actual data parameter is less than the specified value?5 CountsGo to Step 8Go to Step 6
5Test the appropriate signal circuit of the 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 12Go to Step 9
6Test the signal circuit of the appropriate 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 12Go to Step 7
7Test the low reference circuit of the appropriate 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 12Go to Step 9
8Inspect for poor connections at the harness connector of the appropriate air temperature sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition?Go to Step 12Go to Step 10
9Inspect for poor connections at the harness connector of the HVAC control module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition?Go to Step 12Go to Step 11
10Replace the air temperature sensor. Refer to the appropriate replacement procedure: Air Temperature Sensor Replacement - Upper Right Side Air Temperature Sensor Replacement - Upper Left Side Air Temperature Sensor Replacement - Lower Left Side Air Temperature Sensor Replacement - Lower Right Side Did you complete the replacement?Go to Step 12
11Replace the HVAC control module. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement?Go to Step 12
12Use the scan tool in order to clear the DTCs. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text. Does the DTC reset?Go to Step 2System OK

DTC B0174, B0179, B0510, or B0515

The numbers below refer to the step numbers on the diagnostic table.

  1. 2: This step verifies that the value displayed is within the specified range.
  2. 3: This step tests for the proper operation of the circuit in the high voltage range.
  3. 4: This step 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.
StepActionValue(s)YesNo
Schematic Reference: HVAC Schematics Connector End View Reference: HVAC Connector End Views
1Did you perform the Diagnostic System Check - Vehicle?Go to Step 2Go to Diagnostic System Check - Vehicle
2Install a scan tool. Turn ON the ignition, with the engine OFF. With a scan tool, observe the appropriate Solar Sensor parameter in the body control module (BCM) data list. Does the scan tool indicate that the appropriate Solar Sensor parameter is within the specified range?5-250 CountsGo to Testing for Intermittent Conditions and Poor ConnectionsGo to Step 3
3Turn OFF the ignition. Disconnect the sunload sensor assembly. Turn ON the ignition, with the engine OFF. With a scan tool, observe the appropriate Solar Sensor data parameter. Does the scan tool indicate that the appropriate Solar Sensor parameter is greater than the specified value?250 CountsGo to Step 4Go to Step 5
4Turn OFF the ignition. Connect a 3-amp fused jumper wire between the signal circuit of the sunload sensor assembly and the low reference circuit of the sunload sensor assembly. Turn ON the ignition, with the engine OFF. With a scan tool, observe the appropriate Solar Sensor parameter. Does the scan tool indicate that the appropriate Solar Sensor parameter is less than the specified value?5 CountsGo to Step 8Go to Step 6
5Test the appropriate solar signal circuit of the sunload sensor assembly for a short to ground. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition?Go to Step 12Go to Step 9
6Test the appropriate signal circuit of the sunload sensor assembly 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 12Go to Step 7
7Test the low reference circuit of the sunload sensor assembly for a high resistance or an open. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition?Go to Step 12Go to Step 9
8Inspect for poor connections at the harness connector of the sunload sensor assembly. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition?Go to Step 12Go to Step 10
9Inspect for poor connections at the harness connector of the BCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition?Go to Step 12Go to Step 11
10Replace the sunload sensor assembly. Refer to Sun Load Sensor Replacement . Did you complete the replacement?Go to Step 12
11Replace the BCM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement?Go to Step 12
12Use the scan tool in order to clear the DTCs. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text. Does the DTC reset?Go to Step 2System OK

DTC B0183 or B0188

The numbers below refer to the step numbers on the diagnostic table.

  1. 3: At least 2 of the DTCs must be set as current DTC to ensure correct diagnosis. If only one DTC is present then the answer is No.
  2. 5: This step tests for the proper operation of the circuit in the low voltage range.
  3. 6: This step tests for the proper operation of the circuit in the high voltage range. If the jumper fuse opens when you perform this test, the circuit is shorted to ground.
  4. 7: This step tests for a short to voltage in the 5-volt reference circuit.
  5. 8: This step tests for a high resistance or for an open in the low reference circuit.
  6. 9: This step tests for an open on the low reference circuit that is common to all of the actuators. Choose the easiest HVAC door actuator that set a DTC to start the diagnosis.
  7. 10: Disconnecting each actuator, one at a time, isolates the disconnected actuators signal circuit from the 5-volt reference circuit that is common to all the actuators.
StepActionValuesYesNo
Schematic Reference: HVAC Schematics Connector End View Reference: HVAC Connector End Views
1Did you perform the Diagnostic System Check - Vehicle?Go to Step 2Go to Diagnostic System Check - Vehicle
2Is DTC B1375 set as a current DTC?Go to Diagnostic Trouble Code (DTC) List - VehicleGo to Step 3
3With a scan tool, observe the Heating and Air Conditioning DTC list. Does the scan tool indicate that at least 2 of the following DTC B0229, B0414, B0424, and B3770 are set as current DTC?Go to Step 9Go to Step 4
4Install a scan tool. Turn ON the ignition, with the engine OFF. With the scan tool, observe the appropriate Door Actual parameter in the Heating and Air Conditioning data list. Does the scan tool indicate that the appropriate Door Actual parameter is within the specified range?5-250 countsGo to Diagnostic AidsGo to Step 5
5Turn OFF the ignition. Disconnect the appropriate HVAC door actuator. Turn ON the ignition, with the engine OFF. With a scan tool, observe the appropriate Door Actual parameter. Does the scan tool indicate that the appropriate Door Actual parameter is less than the specified value?5 countsGo to Step 6Go to Step 16
6Turn OFF the ignition. Connect a 3-amp fused jumper between the 5-volt reference circuit and the appropriate door position signal circuit of the HVAC door actuator. Turn ON the ignition, with the engine OFF. With a scan tool, observe the appropriate Door Actual parameter. Does the scan tool indicate that the appropriate Door Actual parameter is greater than the specified value?230 countsGo to Step 7Go to Step 14
7Disconnect the fused jumper. Measure the voltage between the 5-volt reference circuit and the low reference circuit of the HVAC door actuator. Does the voltage measure less than the specified value?5.5 VGo to Step 8Go to Step 13
8Turn OFF the ignition. Disconnect the negative battery cable. Measure the resistance from the low reference circuit of the HVAC door actuator to a good ground. Does the resistance measure less than the specified value?5 ohmsGo to Step 18Go to Step 17
9Disconnect the most accessible affected HVAC door actuator. Probe the low reference circuit of the HVAC door actuator with a test lamp from battery positive voltage. Does the test lamp illuminate?Go to Step 10Go to Step 17
10Turn ON the ignition, with the engine OFF. With a scan tool, observe the Heating and Air Conditioning DTC list. While observing DTC list, disconnect and connect the electrical connector for each affected HVAC door actuator. Did the scan tool indicate that only one DTC was present when a HVAC door actuator was disconnected?Go to Step 12Go to Step 11
11Test the 5-volt reference circuit of the appropriate HVAC door actuator for an open. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition?Go to Step 22Go to Step 19
12Test the appropriate door position signal circuit of the HVAC door actuator for a short to ground. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition?Go to Step 22Go to Step 18
13Test the 5-volt reference circuit of the appropriate HVAC door actuator for a short to voltage. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition?Go to Step 22Go to Step 19
14Test the 5-volt reference circuit of the appropriate HVAC door actuator for a short to ground, for a high resistance, or for an open. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition?Go to Step 22Go to Step 15
15Test the appropriate door position signal circuit of the HVAC door actuator for a short to ground, for a high resistance, or for an open. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition?Go to Step 22Go to Step 19
16Test the appropriate door position signal circuit of the HVAC door actuator for a short to voltage. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition?Go to Step 22Go to Step 19
17Disconnect the HVAC control module. Test the low reference circuit of the appropriate HVAC door actuator for a high resistance or for an open. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition?Go to Step 22Go to Step 19
18Inspect for poor connections at the harness connector of the appropriate HVAC door actuator. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition?Go to Step 22Go to Step 20
19Inspect for poor connections at the harness connector of the HVAC control module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition?Go to Step 22Go to Step 21
20IMPORTANT: Perform the calibration procedure for HVAC door actuators. Replace the HVAC door actuator. Refer to the appropriate replacement procedure: Recirculation Actuator Replacement Mode Actuator Replacement (With D07) or Mode Actuator Replacement (Without D07) Air Temperature Actuator Replacement - Right Side Air Temperature Actuator Replacement - Left Side Did you complete the replacement?Go to Step 22
21Replace the HVAC control module. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement?Go to Step 22
22Use the scan tool in order to clear the DTCs. Operate the vehicle according to the Conditions for Running in the DTC, as specified in the supporting text. Does the DTC set again?Go to Step 4System OK
IMPORTANT
Perform the calibration procedure for HVAC door actuators.

DTC B0229, B0414, B0424, or B3770

The numbers below refer to the step numbers on the diagnostic table.

  1. 2: This step determines if the HVAC door actuator is stalled.
  2. 3: This step applies control circuit voltage to the input of the HVAC door actuator.
StepActionYesNo
Schematic Reference: HVAC Schematics Connector End View Reference: HVAC Connector End Views
1Did you perform the Diagnostic System Check - Vehicle?Go to Step 2Go to Diagnostic System Check - Vehicle
2Install a scan tool. Turn ON the ignition, with the engine OFF. With a scan tool, command the appropriate HVAC door actuator ON and OFF while observing the corresponding Door Actual parameter. Does the scan tool indicate that the value of the appropriate Door Actual parameter changes?Go to Diagnostic AidsGo to Step 3
3Observe the appropriate HVAC door actuator drive shaft. Connect a 3-amp fused jumper wire between appropriate door control circuit at the HVAC control module and a good ground. Disconnect the fused jumper wire. Connect a 3-amp fused jumper wire between the appropriate door control circuit and the 5-volt reference circuit at the HVAC control module. Does the drive shaft of the appropriate HVAC door actuator rotate?Go to Step 8Go to Step 4
4Test the door control circuit of the appropriate HVAC door actuator for a short to voltage, for a short to ground, or for an open. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition?Go to Step 12Go to Step 5
5Turn OFF the ignition. Disconnect the fused jumper wire. Disconnect the appropriate HVAC door actuator. Turn ON the ignition, with the engine OFF. Probe the ignition 3-voltage circuit of the appropriate HVAC door actuator with a test lamp that is connected to ground. Does the test lamp illuminate?Go to Step 6Go to Step 9
6Inspect the appropriate door and the door actuator for the following conditions: A misaligned door actuator Binding linkages A binding door An obstruction that prevents the HVAC door actuator from operating within the full range of motion Did you find and correct the condition?Go to Step 12Go to Step 7
7Inspect for poor connections at the harness connector of the appropriate HVAC door actuator. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition?Go to Step 12Go to Step 10
8Inspect for poor connections at the harness connector of the HVAC control module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition?Go to Step 12Go to Step 11
9Repair the ignition 3-voltage circuit of the appropriate HVAC door actuator. Refer to Wiring Repairs . Did you complete the repair?Go to Step 12
10IMPORTANT: Perform the calibration procedure for HVAC door actuators. Replace the appropriate HVAC door actuator. Refer to the appropriate replacement procedure: Recirculation Actuator Replacement Mode Actuator Replacement (With D07) or Mode Actuator Replacement (Without D07) Air Temperature Actuator Replacement - Right Side Air Temperature Actuator Replacement - Left Side Did you complete the replacement?Go to Step 12
11Replace the HVAC control module. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement?Go to Step 12
12Use the scan tool in order to clear the DTCs. Operate the vehicle according to the Conditions for Running in the DTC as specified in the supporting text. Does the DTC set again?Go to Step 2System OK
IMPORTANT
Perform the calibration procedure for HVAC door actuators.

DTC B0263, B0268, B0408, or B0418

The numbers below refer to the step numbers on the diagnostic table.

  1. 2: This step tests to ensure that an air temperature sensor DTC did not cause this DTC.
  2. 5: DTC B0989 sets only for the lower air temperature sensors. They HVAC system is placed in the Bi-Level mode and set to the coldest position to obtain a consistent temperature in the HVAC ducts. This action will determine if one of the air temperature sensors reading may be slightly higher or lower than the other air temperature sensors.
  3. 6: The appropriate air temperature sensor is the sensor that is out of range compared to the other duct air temperature sensors.
StepActionYesNo
Schematic Reference: HVAC Schematics Connector End View Reference: HVAC Connector End Views
1Did you perform the Diagnostic System Check - Vehicle?Go to Step 2Go to Diagnostic System Check - Vehicle
2IMPORTANT: DTC B0174, B0179, B0510 and B0515 must be repaired before this diagnostic is completed or misdiagnosis will occur. Install a scan tool. Turn ON the ignition, with the engine OFF. With a scan tool, monitor the DTC Information for DTC B0174, B0179, B0510 and B0515 in the HVAC control module. Does the scan tool indicate that DTC B0174, B0179, B0510 and B0515 are current?Go to Diagnostic Trouble Code (DTC) List - VehicleGo to Step 3
3With a scan tool, monitor the DTC Information for DTC B0989 in the HVAC control module. Does the scan tool indicate that DTC B0989 is current?Go to Step 4Go to Diagnostic Aids
4Turn ON the ignition with the engine OFF. Observe the RH Heater Duct Actual and the LH Heater Duct Actual parameters in the HVAC control module data list. Are the RH Heater Duct Actual and the LH Heater Duct Actual parameters within 30 counts of each other?Go to Diagnostic AidsGo to Step 5
5Start the engine. Place the mode switch to the Bi-Level position. Place the left and right air temperature switches to the coldest position. Place the A/C switch to the ON position. Wait 5 minutes. Observe the RH Heater Duct Actual, LH Heater Duct Actual, RH AC Duct Actual and the LH AC Duct Actual parameters in the HVAC control module data list. Compare all air temperature sensors count value. Is one the Heater Duct Actual parameters not within 30 counts of the other air temperature sensors count value?Go to Step 6Go to Diagnostic Aids
6Inspect the appropriate air temperature sensor for proper installation. Refer to the appropriate procedure: Air Temperature Sensor Replacement - Lower Left Side Air Temperature Sensor Replacement - Lower Right Side Did you find and correct the condition?Go to Step 14Go to Step 7
7Turn OFF the ignition. Disconnect the appropriate air temperature sensor. Turn ON the ignition, with the engine OFF. Measure the voltage from the signal circuit of the appropriate air temperature sensor to a good ground. Does the voltage measure 4.9 volts or more?Go to Step 8Go to Step 10
8Test the signal circuit of the appropriate air temperature sensor for the following: An open A high resistance A short to ground A short to voltage Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition?Go to Step 14Go to Step 9
9Test the low reference circuit of the appropriate 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 14Go to Step 11
10Inspect for poor connections at the harness connector of the HVAC control module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition?Go to Step 14Go to Step 13
11Inspect for poor connections at the harness connector of the appropriate air temperature sensor assembly. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition?Go to Step 14Go to Step 12
12Replace the air temperature sensor assembly. Refer to the appropriate replacement procedure: Air Temperature Sensor Replacement - Lower Left Side Air Temperature Sensor Replacement - Lower Right Side Did you complete the replacement?Go to Step 14
13Replace the HVAC control module. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement?Go to Step 14
14Use the scan tool in order to clear the DTCs. Operate the vehicle within normal operating conditions. Does the DTC reset?Go to Step 2System OK
IMPORTANT
DTC B0174, B0179, B0510 and B0515 must be repaired before this diagnostic is completed or misdiagnosis will occur.

DTC B0989

The numbers below refer to the step numbers on the diagnostic table.

  1. 2: This step tests to ensure that an air temperature sensor DTC did not cause this DTC.
  2. 5: DTC B0989 sets only for the lower air temperature sensors. The HVAC system is placed in the Bi-Level mode and set to the coldest position to obtain a consistent temperature in the HVAC ducts. This action will determine if one of the air temperature sensors reading may be slightly higher or lower than the other air temperature sensors.
  3. 6: The appropriate air temperature sensor is the sensor that is out of range compared to the other duct air temperature sensors.
StepActionYesNo
Schematic Reference: HVAC Schematics Connector End View Reference: HVAC Connector End Views
1Did you perform the Diagnostic System Check - Vehicle?Go to Step 2Go to Diagnostic System Check - Vehicle
2IMPORTANT: DTC B0174, B0179, B0510 and B0515 must be repaired before this diagnostic is completed or misdiagnosis will occur. Install a scan tool. Turn ON the ignition, with the engine OFF. With a scan tool, monitor the DTC Information for DTC B0174, B0179, B0510 and B0515 in the HVAC control module. Does the scan tool indicate that DTC B0174, B0179, B0510 and B0515 are current?Go to Diagnostic Trouble Code (DTC) List - VehicleGo to Step 3
3With a scan tool, monitor the DTC Information for DTC B0990 in the HVAC control module. Does the scan tool indicate that DTC B0990 is current?Go to Step 4Go to Diagnostic Aids
4Turn ON the ignition with the engine OFF. Observe the RH AC Duct Actual and the LH AC Duct Actual parameters in the HVAC control module data list. Are the RH Heater Duct Actual and the LH Heater Duct Actual parameters within 30 counts of each other?Go to Diagnostic AidsGo to Step 5
5Start the engine. Place the mode switch to the Bi-Level position. Place the left and right air temperature switches to the coldest position. Place the A/C switch to the ON position. Wait 5 minutes. Observe the RH Heater Duct Actual, LH Heater Duct Actual, RH AC Duct Actual and the LH AC Duct Actual parameters in the HVAC control module data list. Compare all air temperature sensors count value. Is one the AC Duct Actual parameters not within 30 counts of the other air temperature sensors count value?Go to Step 6Go to Diagnostic Aids
6Inspect the appropriate air temperature sensor for proper installation. Refer to the appropriate procedure: Air Temperature Sensor Replacement - Lower Left Side Air Temperature Sensor Replacement - Lower Right Side Did you find and correct the condition?Go to Step 14Go to Step 7
7Turn OFF the ignition. Disconnect the appropriate air temperature sensor. Turn ON the ignition, with the engine OFF. Measure the voltage from the signal circuit of the appropriate air temperature sensor to a good ground. Does the voltage measure 4.9 volts or more?Go to Step 8Go to Step 10
8Test the signal circuit of the appropriate air temperature sensor for the following: An open A high resistance A short to ground A short to voltage Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition?Go to Step 14Go to Step 9
9Test the low reference circuit of the appropriate 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 14Go to Step 11
10Inspect for poor connections at the harness connector of the HVAC control module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition?Go to Step 14Go to Step 13
11Inspect for poor connections at the harness connector of the appropriate air temperature sensor assembly. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition?Go to Step 14Go to Step 12
12Replace the air temperature sensor assembly. Refer to the appropriate replacement procedure: Air Temperature Sensor Replacement - Upper Right Side Air Temperature Sensor Replacement - Upper Left Side Did you complete the replacement?Go to Step 14
13Replace the HVAC control module. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement?Go to Step 14
14Use the scan tool in order to clear the DTCs. Operate the vehicle within normal operating conditions. Does the DTC reset?Go to Step 2System OK
IMPORTANT
DTC B0174, B0179, B0510 and B0515 must be repaired before this diagnostic is completed or misdiagnosis will occur.

DTC B0990

The numbers below refer to the step numbers on the diagnostic table.

  1. 3: This step tests for the proper operation of the circuit in the low voltage range.
  2. 4: This step tests for the proper operation of the circuit in the high voltage range. If the fuse in the jumper opens when you perform this test, the signal circuit is shorted to ground.
  3. 5: This step tests for a short to voltage in the 5-volt reference circuit.
  4. 6: This step tests for a high resistance or an open in the low reference circuit.
StepActionValuesYesNo
Schematic Reference: HVAC Schematics Connector End View Reference: HVAC Connector End Views
1Did you perform the Diagnostic System Check - Vehicle?Go to Step 2Go to Diagnostic System Check - Vehicle
2Turn ON the ignition with the engine OFF. With a scan tool, observe the A/C Pressure Sensor parameter in the Powertrain Engine Data list. Does the scan tool indicate the A/C Pressure Sensor parameter is within the specified range?0.1-4.9 VGo to Diagnostic AidsGo to Step 3
3Turn OFF the ignition. Disconnect the A/C refrigerant pressure sensor. Turn ON the ignition, with the engine OFF. With a scan tool, observe the A/C Pressure Sensor parameter. Does the scan tool indicate that the A/C Pressure Sensor parameter is less than the specified value?0.09 VGo to Step 4Go to Step 10
4Turn OFF the ignition. Connect a 3-amp fused jumper wire between the 5-volt reference circuit of the A/C refrigerant pressure sensor and the signal circuit of the A/C refrigerant pressure sensor. Turn ON the ignition, with the engine OFF. With a scan tool, observe the A/C Pressure Sensor parameter. Does the scan tool indicate that the A/C Pressure Sensor parameter is greater than the specified value?4.9 VGo to Step 8Go to Step 5
5Disconnect the fused jumper wire. Measure the voltage between the 5-volt reference circuit of the A/C refrigerant pressure sensor and the low reference circuit of the A/C refrigerant pressure sensor. Does the voltage measure less than the specified value?5.1 VGo to Step 6Go to Step 7
6Turn OFF the ignition. Disconnect the negative battery cable. Measure the resistance from the low reference circuit of the A/C refrigerant pressure sensor to a good ground. Does the resistance measure less than the specified value?5 ohmsGo to Step 12Go to Step 11
7Test the 5-volt reference circuit of the A/C refrigerant pressure sensor for a short to voltage. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition?Go to Step 16Go to Step 13
8Test the 5-volt reference circuit of the A/C refrigerant pressure sensor for a short to ground, a high resistance, or an open. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition?Go to Step 16Go to Step 9
9Test the signal circuit of the A/C refrigerant pressure sensor for a short to ground, a high resistance, or an open. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition?Go to Step 16Go to Step 13
10Test the signal circuit of the A/C refrigerant pressure sensor for a short to voltage. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition?Go to Step 16Go to Step 13
11Disconnect the powertrain control module (PCM)/engine control module (ECM). Test the low reference circuit of the A/C refrigerant pressure 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 16Go to Step 13
12Inspect for poor connections at the harness connector of the A/C refrigerant pressure sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition?Go to Step 16Go to Step 14
13Inspect for poor connections at the harness connector of the PCM or ECM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition?Go to Step 16Go to Step 15
14Replace the A/C refrigerant pressure sensor. Refer to Air Conditioning (A/C) Refrigerant Pressure Sensor Replacement . Did you complete the replacement?Go to Step 16Go to Step 15
15Replace the PCM/ECM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement?Go to Step 16
16Use the scan tool in order to clear the DTCs. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text. Does the DTC reset?Go to Step 2System OK

DTC P0530 (LU3, LR4, LM7, LQ4 and L18)

The number below refers to the step number on the diagnostic table.

  1. 5: This step tests the ability of the A/C refrigerant pressure sensor to create a voltage signal for the ECM to monitor the A/C refrigerant pressure. Measure the voltage at the A/C refrigerant pressure sensor, if the voltage is measured at the connector for the sensor, misdiagnosis will occur.
StepActionValue(s)YesNo
Schematic Reference: HVAC Schematics Connector End View Reference: HVAC Connector End Views
1Did you perform the Diagnostic System Check - Vehicle?Go to Step 2Go to Diagnostic System Check - Vehicle
2Does the scan tool indicate that DTC P0530 is current?Go to Step 3Go to Diagnostic Aids
3Turn OFF the ignition. Disconnect the A/C refrigerant pressure sensor. Turn ON the ignition, with the engine OFF. Measure the voltage from the 5-volt reference circuit to the low reference circuit of the A/C refrigerant pressure sensor. Does the voltage measure near the specified value?5 VGo to Step 5Go to Step 4
4Measure the voltage from the 5-volt reference circuit of the A/C refrigerant pressure sensor to a good ground. Does the voltage measure near the specified value?5 VGo to Step 7Go to Step 6
5With the A/C refrigerant pressure sensor disconnected, connect a jumper wire between the A/C refrigerant pressure sensor and the electrical connector of the A/C refrigerant pressure sensor for the following circuits: The 5-volt reference circuit The low reference circuit Measure the voltage at the A/C refrigerant pressure sensor terminal for the A/C refrigerant pressure sensor signal. Does the voltage measure less than the specified value?1.5 VGo to Step 8Go to Step 9
6Test the 5-volt reference circuit of the A/C refrigerant pressure sensor for the following: A short to ground A short to voltage A high resistance An open Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition?Go to Step 13Go to Step 10
7Test the low reference circuit of the A/C refrigerant pressure 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 13Go to Step 10
8Test the signal circuit of the A/C refrigerant pressure sensor for the following: A short to ground A short to voltage A high resistance An open Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition?Go to Step 13Go to Step 10
9Inspect for poor connections at the harness connector of the A/C refrigerant pressure sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition?Go to Step 13Go to Step 11
10Inspect for poor connections at the harness connector of the engine control module (ECM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition?Go to Step 13Go to Step 12
11Replace the A/C refrigerant pressure sensor. Refer to Air Conditioning (A/C) Refrigerant Pressure Sensor Replacement . Did you complete the replacement?Go to Step 13
12Replace the ECM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement?Go to Step 13
13Use the scan tool in order to clear the DTCs. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text. Does the DTC reset?Go to Step 2System OK

DTC P0532 or P0533

Symptoms - HVAC Systems - Automatic

IMPORTANTThe following steps must be completed before using the symptom tables.
  1. Perform the «Diagnostic System Check - Vehicle»(ref-277883-S07139257572008012100000) , before using the Symptom Tables in order to verify that all of the following are true: There are no DTCs set. The control modules can communicate via the serial data link.
  2. Review the system operation in order to familiarize yourself with the system functions. Refer to the following information: «Air Delivery Description and Operation»(ref-277856-S28332698802008012100000) «Air Temperature Description and Operation»(ref-277856-S14847472002008012100000)

The numbers below refer to the step numbers on the diagnostic table.

  1. 2: The A/C compressor output is disabled if the engine is idling at a low unstable RPM.
  2. 3: The A/C compressor relay output is disabled if engine coolant temperature is above 121°C (250°F). The engine coolant indicator will illuminate at this temperature.
  3. 4: This step ensures that the HVAC control module is receiving an input from the A/C switch.
  4. 5: These actions will enable the A/C compressor to operate.
  5. 6: This test ensures that there is sufficient refrigerant in the A/C system. The specific values come from the A/C System Performance Test in Heating, Ventilation and Air Conditioning.
  6. 8: The A/C Low Pressure Switch parameter is out of range when the HVAC control module interprets the signal being below 138-172 kPa (20-25 psi).
  7. 9: This action will simulate a closed switch condition. If the Pressure Cycle Switch parameter reads Low Pressure than there is a circuit condition or a condition with the HVAC control module.
  8. 12: The A/C compressor relay output from the PCM is disabled if the A/C high side system pressure is interpreted to be higher than 2 958 kPa (429 psi).
StepActionValuesYesNo
Schematic Reference: HVAC Schematics (Manual - CJ3) or HVAC Schematics (Blower Control - C42) Connector End View Reference: HVAC Connector End Views DEFINITION: The A/C compressor clutch will not engage when an A/C request has been made and a Powertrain DTC has not been set.
1Did you perform the Diagnostic System Check - Vehicle?Go to Step 2Go to Diagnostic System Check - Vehicle
2Start the engine. Set the parking brake. Place the vehicle in drive and allow the engine to idle. Observe the engine RPM. Does the engine idle at a steady RPM?Go to Step 3Go to Rough, Unstable, or Incorrect Idle and Stalling for the 4.8L, 5.3L and 6.0L Engine Rough, Unstable, or Incorrect Idle and Stalling for the 4.3L Engine Rough, Unstable, or Incorrect Idle and Stalling for the 8.1L Engine
3Start the engine. Observe the coolant temperature indicator. Is the engine coolant temperature indicator illuminated?Go to Diagnostic Trouble Code (DTC) List - VehicleGo to Step 4
4Install a scan tool. Turn ON the ignition, with the engine OFF. With a scan tool, observe the A/C Switch parameter in the Heating and Air Conditioning data list. Activate the A/C request switch. Does the scan tool indicate that the A/C Switch parameter changes states?Go to Step 5Go to Step 26
5IMPORTANT: For A/C compressor operation, the ambient air temperature must be above 5°C (40°F). Start the engine. Place the blower motor switch in the maximum speed position. Place the A/C request switch in the ON position. Place the left air temperature switch in the coldest position. Does the A/C compressor clutch engage?Go to Testing for Intermittent Conditions and Poor ConnectionsGo to Step 6
6Park the vehicle inside or out of direct sunlight. Open the window in order to ventilate the interior of the vehicle. Turn OFF the ignition. If the A/C system was operating, then wait for approximately 2 minutes. Install J 43600 ACR 2000 Air Conditioning Service Center. Record the ambient temperature at the vehicle. Record readings of the low and high side STATIC pressures. Compare the low and the high side pressure values with the allowable limits for the recorded ambient air temperature. Are the low and the high side pressure values within the allowable limits for the recorded ambient air temperature. Are the pressure values within 103 kPa (15 psi) of each other?Above 16°C (60°F) 345 kPa (50 psi) Above 24°C (75°F) 483 kPa (70 psi) Above 33°C (90°F) 690 kPa (100 psi)Go to Step 7Go to Leak Testing
7Start the engine. With a scan tool, observe the A/C Permission parameter in the Heating and Air Conditioning data list. Does the A/C Permission parameter display Granted?Go to Step 14Go to Step 8
8Turn OFF the ignition. Turn ON the ignition, with the engine OFF. With a scan tool, observe the Pressure Cycle Switch parameter in the Heating and Air Conditioning data list. Does the Pressure Cycle Switch parameter display Normal?Go to Step 12Go to Step 9
9Turn OFF the ignition. Disconnect the A/C low pressure switch. Turn ON the ignition, with the engine OFF. Connect a 3-ampere fused jumper between the signal circuit and the ground circuit of the A/C low pressure switch. Observe the Pressure Cycle Switch parameter in the Heating and Air Conditioning data list. Does the Pressure Cycle Switch parameter display Normal?Go to Step 23Go to Step 10
10Test the signal circuit of the A/C low pressure switch for a high resistance or for an open. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition?Go to Step 35Go to Step 11
11Test the ground circuit of the A/C low pressure switch for a high resistance or for an open. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition?Go to Step 35Go to Step 26
12With a scan tool, observe the A/C Pressure Sensor parameter in the Powertrain Engine data list. Is the parameter less than the specified value?2958 kPa (429 psi)Go to Step 26Go to Step 13
13Turn OFF the ignition. If the A/C system was operating, then wait for approximately 2 minutes. Install J 43600 . Turn ON the ignition, with the engine OFF. With a scan tool, observe the A/C Pressure Sensor parameter. Compare the A/C Pressure Sensor parameter on the scan tool to the A/C high side pressure on J 43600 . Are the high side pressure values within 103 kPa (15 psi) of each other?Go to Air Conditioning (A/C) System Performance Test (Diesel Engine) or Air Conditioning (A/C) System Performance Test (Gas Engine w/Electric Cooling Fan) or Air Conditioning (A/C) System Performance Test (Gas Engine w/Engine Driven Fan)Go to Step 24
14Start the engine. With a scan tool, command the A/C Permission to Granted and Withheld. Does the relay turn ON and OFF with each command?Go to Step 15Go to Step 19
15Turn OFF the ignition. Test the battery positive voltage circuit of the A/C compressor clutch relay for a high resistance or for an open. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition?Go to Step 35Go to Step 16
16Turn OFF the ignition. Connect a 10-ampere fused jumper between the battery positive circuit of the A/C compressor relay and the A/C compressor supply voltage circuit. Disconnect the A/C compressor connector. Turn ON the ignition, with engine OFF. Connect a test lamp between the A/C compressor supply voltage circuit and the ground circuit of the A/C compressor. Does the test light illuminate?Go to Step 25Go to Step 17
17Test the supply voltage circuit of the A/C compressor clutch for a high resistance or for an open. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition?Go to Step 35Go to Step 18
18Test the ground circuit of the A/C compressor clutch for a high resistance or for an open. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition?Go to Step 35Go to Step 22
19Turn OFF the ignition. Disconnect the A/C compressor clutch relay. Turn ON the ignition, with the engine OFF. Probe the ignition 3 voltage circuit of the A/C compressor clutch relay with a test lamp that is connected to ground. Does the test lamp illuminate?Go to Step 20Go to Step 28
20Start the engine. Connect a test lamp between the control circuit and the ignition 3 voltage circuit of the A/C compressor clutch relay. With a scan tool, command the A/C Permission to Granted. Does the test lamp illuminate?Go to Step 22Go to Step 21
21Turn OFF the ignition. Test the A/C compressor clutch control circuit of the A/C compressor clutch relay for a high resistance or for an open. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition?Go to Step 35Go to Step 27
22Turn OFF the ignition. Inspect for poor connections at the A/C compressor clutch relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition?Go to Step 35Go to Step 29
23Inspect for poor connections at the harness connector of the A/C low pressure switch. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition?Go to Step 35Go to Step 30
24Inspect for poor connections at the harness connector of the A/C refrigerant pressure sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition?Go to Step 35Go to Step 31
25Inspect for poor connections at the harness connector of the A/C compressor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition?Go to Step 35Go to Step 32
26Inspect for poor connections at the harness connector of the HVAC control module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition?Go to Step 35Go to Step 33
27Inspect for poor connections at the harness connector of the powertrain control module (PCM) or engine control module (ECM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition?Go to Step 35Go to Step 34
28Repair the ignition 3 voltage circuit of the A/C compressor clutch relay. Refer to Wiring Repairs . Did you complete the repair?Go to Step 35
29Replace the A/C compressor clutch relay. Did you complete the replacement?Go to Step 35
30Replace the A/C low pressure switch. Refer to Air Conditioning (A/C) Low Pressure Switch Replacement . Did you complete the replacement?Go to Step 35
31Replace the A/C refrigerant pressure sensor. Refer to Air Conditioning (A/C) Refrigerant Pressure Sensor Replacement . Did you complete the replacement?Go to Step 35
32Replace the A/C compressor clutch. Refer to Compressor Clutch Plate/Hub Assembly Replacement (4.8L, 5.3L, 6.0L and 8.1L) or Compressor Clutch Plate/Hub Assembly Replacement (4.3L, 6.6L) . Did you complete the replacement?Go to Step 35
33Replace the HVAC control module. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement?Go to Step 35
34Replace the PCM/ECM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement?Go to Step 35
35Operate the system in order to verify the repair. Did you correct the condition?System OKGo to Step 5
IMPORTANT
For A/C compressor operation, the ambient air temperature must be above 5°C (40°F).

HVAC Compressor Clutch Does Not Engage

The number below refers to the step number on the diagnostic table.

  1. 2: These actions will disable the HVAC control module output to powertrain control module (PCM) or engine control module (ECM).
StepActionYesNo
Schematic Reference: HVAC Schematics Connector End View Reference: HVAC Connector End Views DEFINITION: The A/C compressor clutch will not disengage when an A/C request has not been made and a Powertrain DTC has not been set.
1Did you perform the Diagnostic System Check - Vehicle?Go to Step 2Go to Diagnostic System Check - Vehicle
2Start the engine. Place the mode switch in the PANEL position. Place the A/C request switch in the OFF position. Does the A/C compressor clutch engage?Go to Step 3Go to Testing for Intermittent Conditions and Poor Connections
3Turn OFF the ignition. Disconnect the A/C compressor clutch. Turn ON the ignition, with the engine OFF. Probe the supply voltage circuit of the A/C compressor clutch with a test lamp that is connected to ground. Does the test lamp illuminate?Go to Step 4Go to Step 8
4Test the supply voltage circuit of the A/C compressor clutch for a short to voltage. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition?Go to Step 13Go to Step 5
5Turn OFF the ignition. Disconnect the A/C compressor clutch relay. Turn ON the ignition, with the engine OFF. Connect a test lamp between the control circuit and the ignition 3 voltage circuit of the A/C compressor clutch relay. Does the test lamp illuminate?Go to Step 6Go to Step 7
6Test the control circuit of the A/C compressor clutch relay for a short to ground. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition?Go to Step 13Go to Step 9
7Inspect for poor connections at the A/C compressor clutch relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition?Go to Step 13Go to Step 10
8Inspect for poor connections at the harness connector of the A/C compressor clutch. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition?Go to Step 13Go to Step 11
9Inspect for poor connections at the harness connector of the powertrain control module (PCM) or engine control module (ECM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition?Go to Step 13Go to Step 12
10Replace the A/C compressor clutch relay. Did you complete the replacement?Go to Step 13
11Replace the A/C compressor. Refer to Compressor Replacement (L18) or Compressor Replacement (LLY/LMM) or Compressor Replacement (LR4, LM7, L59 and LQ4) or Compressor Replacement (LU3) . Did you complete the replacement?Go to Step 13
12Replace the PCM/ECM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement?Go to Step 13
13Operate the system in order to verify the repair. Did you correct the condition?System OKGo to Step 3

HVAC Compressor Clutch Does Not Disengage

The number below refers to the step number on the diagnostic table.

  1. 4: The blower motor parameter must be commanded ON before an OFF command will function.
StepActionValuesYesNo
Schematic Reference: HVAC Schematics Connector End View Reference: HVAC Connector End Views DEFINITION: The blower motor operates with the HVAC controls in the OFF position.
1Did you perform the Diagnostic System Check - Vehicle?Go to Step 2Go to Diagnostic System Check - Vehicle
2Turn the ignition ON, with the engine OFF. Turn OFF the HVAC controls. Is the blower motor OFF?Go to Testing for Intermittent Conditions and Poor ConnectionsGo to Step 3
3With a scan tool observe the Blower Motor PWM Speed parameter in the Heating and Air Conditioning data list. Does the scan tool indicate that the Blower Motor PWM Speed parameter is near the specified value?0%Go to Step 4Go to Step 6
4With a scan tool, command the Blower Motor parameter ON in the Heating and Air Conditioning Scan Tool Output Controls. Command the Blower Motor parameter OFF. Does the blower motor turn OFF?Go to Step 6Go to Step 5
5Inspect for poor connections at the harness connector of the blower motor control processor. Refer to Wiring Repairs and Connector Repairs . Did you find and correct the condition?Go to Step 9Go to Step 7
6Inspect for poor connections at the harness connector of the HVAC control module. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition?Go to Step 9Go to Step 8
7Replace the blower motor control processor. Refer to Blower Motor Control Processor Replacement . Did you complete the replacement?Go to Step 9
8Replace the HVAC control module. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement?Go to Step 9
9Operate the system in order to verify the repair. Did you correct the condition?System OKGo to Step 2

Blower Motor Always On

  1. 2: This step verifies that the HVAC control module Fan Up Switch parameter matches the requested state of the blower motor switch.
  2. 3: This step verifies that the HVAC control module Fan Down Switch parameter matches the requested state of the blower motor switch.
StepActionValuesYesNo
Schematic Reference: HVAC Schematics Connector End View Reference: HVAC Connector End Views DEFINITION: The blower motor operates in at least one speed position.
1Did you perform the Diagnostic System Check - Vehicle?Go to Step 2Go to Diagnostic System Check - Vehicle
2Turn ON the ignition, with the engine OFF. With a scan tool, observe the Fan Up Button parameter in the Heating and Air Conditioning data list. Activate the fan up switch. Does the scan tool indicate that the Fan Up Button parameter changes state?Go to Step 3Go to Step 10
3With a scan tool, observe the Fan Down Button parameter in the Heating and Air Conditioning data list. Activate the fan down switch. Does the scan tool indicate that the Fan Down Button parameter changes state?Go to Step 4Go to Step 10
4Place the blower motor switch in each speed position. Does the blower motor operate at the desired speeds?Go to Testing for Intermittent Conditions and Poor ConnectionsGo to Step 5
5Disconnect the harness connector of the blower motor control processor. Measure the voltage between the battery positive voltage circuit and the ground circuit of the blower motor control processor. Does the voltage measure within the specified range?10-14 VGo to Step 6Go to Step 8
6Connect the blower motor control processor. Disconnect the harness connector of the HVAC control module. Measure the voltage on the blower motor speed control circuit. Does the voltage measure within the specified range?4.5-5.5 VGo to Step 9Go to Step 7
7Test the control circuit of the blower motor control processor for a high resistance. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition?Go to Step 14Go to Step 9
8Test the battery positive voltage circuit of the blower motor control processor for a high resistance. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition?Go to Step 14Go to Step 11
9Inspect for poor connections at the harness connector of the blower motor control processor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition?Go to Step 14Go to Step 12
10Inspect for poor connections at the harness connector of the HVAC control module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition?Go to Step 14Go to Step 13
11Repair a high resistance in the ground circuit of the blower motor control processor. Refer to Circuit Testing . Did you complete the repair?Go to Step 14
12Replace the blower motor control processor. Refer to Blower Motor Control Processor Replacement . Did you complete the replacement?Go to Step 14
13Replace the HVAC control module. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement?Go to Step 14
14Operate the system in order to verify the repair. Did you correct the condition?System OKGo to Step 2

Blower Motor Malfunction

The numbers below refer to the step numbers on the diagnostic table.

  1. 6: The ambient air temperature (AAT) must be above 5°C (40°F) in order for this A/C compressor test to be run.
  2. 8: This step ensures that the lower air temperature sensors operate properly. The LH and RH Heater Duct Actual parameter count values should lower as the air temperature of the ducts get warmer. If there is a high resistance in either of the air temperature sensors circuits or the sensor itself then the count value of the effected sensor would remain high.
  3. 9: This step ensures that the upper air temperature sensors operate properly. The LH and RH AC Duct Actual parameter count values should lower as the air temperature of the ducts get warmer. If there is a high resistance in either of the air temperature sensors circuits or the sensor itself then the count value of the effected sensor would remain high.
  4. 11: This action ensures that the internal fan of the inside air temperature sensor assembly is providing air flow across the internal sensor.
  5. 14: Use the following table to determine that the recorded scan tool values are within range for the recorded probe temperatures of the J 43600 ACR 2000 Air Conditioning Service Center.
Temperature °CTemperature °FScan Tool Display
0-432-40206-175 counts
5-941-49194-161 counts
10-1450-58180-145 counts
15-1959-67166-133 counts
20-2468-76150-119 counts
25-2977-85136-106 counts
30-3486-94121-93 counts
35-3995-103107-81 counts
40-44104-11294-69 counts
45-49113-12183-59 counts
50-54122-13072-51 counts
55-59131-13963-44 counts
60-64140-14855-37 counts

Too Hot in Vehicle

StepActionYesNo
Schematic Reference: HVAC Schematics Connector End View Reference: HVAC Connector End Views DEFINITION: Temperature can not be adjusted, or cooling insufficient during A/C operation.
1Did you perform the Diagnostic System Check - Vehicle?Go to Step 2Go to Diagnostic System Check - Vehicle
2IMPORTANT: If during this diagnostic procedure the HVAC control module is disconnected a recalibration of actuators must be performed to avoid misdiagnosis. Recalibrate actuators. Refer to Actuator Recalibration . Turn ON the ignition, with the engine OFF. Observe the Diagnostic Trouble Code (DTC) List - Vehicle . Does the scan tool display any DTC B0229, B0414, B0424 or B3770?Go to Diagnostic Trouble Code (DTC) List - VehicleGo to Step 3
3Turn ON the ignition, with the engine OFF. Place the blower motor switch in each speed position. Does the blower motor operate in any speed?Go to Step 4Go to Blower Motor Inoperative
4Does the blower motor operate in each speed?Go to Step 5Go to Blower Motor Malfunction
5Place the mode switch in the PANEL position. Place the recirculation switch in the ON position. Observe the recirculation door. Place the recirculation switch in the OFF position. Does the recirculation door move from the recirculation position to the outside air position?Go to Step 6Go to Air Recirculation Malfunction
6Start the engine. Observe the A/C compressor clutch. Place the A/C request switch in the ON position. Does the A/C compressor engage?Go to Step 7Go to HVAC Compressor Clutch Does Not Engage
7Perform the refrigerant system performance test. Refer to Air Conditioning (A/C) System Performance Test (Diesel Engine) or Air Conditioning (A/C) System Performance Test (Gas Engine w/Electric Cooling Fan) or Air Conditioning (A/C) System Performance Test (Gas Engine w/Engine Driven Fan) . Did you find and correct the condition?Go to Step 31Go to Step 8
8Start the engine. Wait until engine coolant temperature (ECT) reaches its normal operating temperature. Place the mode switch to the FLOOR position. Place the driver air temperature switch to the warmest position. With a scan tool, observe the right and left Heater Duct Actual and Heater Duct Desired parameters. Wait 3 minutes to allow the duct air temperature to stabilize. Do both of the Heater Duct Actual parameter values increase within 15 Counts of the Heater Duct Desired parameter?Go to Step 9Go to Step 21
9Place the mode switch to the PANEL position. Place the driver air temperature switch to the warmest position. With a scan tool, observe the right and left AC Duct Actual and AC Duct Desired parameters. Wait 3 minutes to allow the duct air temperature to stabilize. Do both of the AC Duct Actual parameter values increase within 15 Counts of the AC Duct Desired parameter?Go to Step 10Go to Step 21
10Check the air temperature sensors for proper installation. Refer to the following procedures: Air Temperature Sensor Replacement - Upper Right Side Air Temperature Sensor Replacement - Upper Left Side Air Temperature Sensor Replacement - Lower Left Side Air Temperature Sensor Replacement - Lower Right Side Inside Air Temperature Sensor Assembly Replacement Did you find and correct the condition?Go to Step 31Go to Step 11
11Turn ON the ignition, with the engine OFF. Inspect for air flow through the inside air temperature sensor assembly by placing a 5 cm (2 in) square piece of paper over the sensor air inlet. Does the paper stay in place?Go to Step 12Go to Step 17
12Install a scan tool. With a scan tool, observe the Left Solar Sensor and Right Solar Sensor parameters in the Body Control Module (BCM) data list. Direct a light source at the left and right sides of the sunload sensor assembly. Does the scan tool indicate that the values of the Left Solar Sensor and the Right Solar Sensor parameters change?Go to Step 13Go to Step 25
13Place the temperature probe of the J 43600 ACR 2000 Air Conditioning Service Center near the inside air temperature sensor assembly. With a scan tool, observe the Inside Air Temp parameter in the Heating and Air Conditioning Data list. Does the scan tool indicate that the sensor temperature is within 3°C (5°F) of the thermometer temperature?Go to Step 14Go to Step 20
14Start the engine. Place the blower motor switch in the MAXIMUM SPEED position. Place the left and right air temperature switches in the FULL COLD positions. Place the mode switch in the BI-LEVEL position. Wait 3 minutes to allow the discharge air temperatures to stabilize. With a scan tool, record the values of the following parameters in the Heating and Air Conditioning data list: LH AC Duct Actual LH Heater Duct Actual RH AC Duct Actual RH Heater Duct Actual With the temperature probes of the J 43600 , record the air temperatures near the following sensors: The left upper air temperature sensor The left lower air temperature sensor The right upper air temperature sensor The right lower air temperature sensor Are the parameter values within the specified range for the recorded air temperatures?Go to Diagnostic AidsGo to Step 15
15Turn OFF the ignition. Disconnect the suspect air temperature sensor. Place the temperature probe of the J 43600 near the air temperature sensor. Record the probe temperature. Measure the resistance of the air temperature sensor. Refer to the Sensor Resistance Table (Primary HVAC) . Does the resistance measure within the specified range ?Go to Step 16Go to Step 24
16Test the signal circuit and the low reference circuit of the suspect air temperature sensor for a high resistance. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition?Go to Step 31Go to Step 26
17Turn the ignition OFF. Disconnect the inside air temperature sensor assembly. Turn ON the ignition, with the engine OFF. Probe the fan motor supply voltage circuit of the inside air temperature sensor assembly with a test lamp that is connected to a good ground. Does the test lamp illuminate?Go to Step 19Go to Step 18
18Test the fan motor supply voltage circuit of the inside air temperature sensor assembly for an open, a high resistance, or a short to ground. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition?Go to Step 31Go to Step 26
19Test the ground circuit of the inside air temperature sensor for an open or high resistance. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition?Go to Step 31Go to Step 23
20Turn OFF the ignition. Disconnect the inside air temperature assembly. Place the temperature probe of the J 43600 near the inside air temperature sensor assembly. Record the probe temperature. Measure the resistance of the inside air temperature sensor. Refer to Sensor Resistance Table (Primary HVAC) . Does the resistance measure within the specified range ?Go to Step 22Go to Step 23
21Test the signal circuit and the low reference circuit of the appropriate air temperature sensor for a high resistance. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition?Go to Step 31Go to Step 24
22Test the signal circuit and the low reference circuit of the inside air temperature sensor for a high resistance. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition?Go to Step 31Go to Step 26
23Inspect for poor connections at the harness connector of the inside air temperature sensor assembly. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition?Go to Step 31Go to Step 29
24Inspect for poor connections at the harness connector of the appropriate air temperature sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition?Go to Step 31Go to Step 27
25Inspect for poor connections at the harness connector of the sunload sensor assembly. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition?Go to Step 31Go to Step 28
26Inspect for poor connections at the harness connector of the HVAC control module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition?Go to Step 31Go to Step 30
27Replace the appropriate air temperature sensor. Refer to one of the following procedures: Air Temperature Sensor Replacement - Upper Right Side Air Temperature Sensor Replacement - Upper Left Side Air Temperature Sensor Replacement - Lower Left Side Air Temperature Sensor Replacement - Lower Right Side Did you complete the replacement?Go to Step 31
28Replace the sunload sensor. Refer to Sun Load Sensor Replacement . Did you complete the replacement?Go to Step 31
29Replace the inside air temperature sensor. Refer to Inside Air Temperature Sensor Assembly Replacement . Did you complete the replacement?Go to Step 31
30Replace the HVAC control module. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement?Go to Step 31
31Operate the system in order to verify the repair. Did you correct the condition?System OKGo to Step 2
IMPORTANT
If during this diagnostic procedure the HVAC control module is disconnected a recalibration of actuators must be performed to avoid misdiagnosis.

Too Hot in Vehicle

The numbers below refer to the step numbers in the diagnostic table.

  1. 10: This step ensures that the lower air temperature sensors operate properly. The LH and RH Heater Duct Actual parameter count values should lower as the air temperature of the ducts get warmer. If there is a high resistance in either of the air temperature sensor circuits or the sensor itself, then the count value of the affected sensor would remain high.
  2. 11: This step ensures that the upper air temperature sensors operate properly. The LH and RH AC Duct Actual parameter count values should lower as the air temperature of the ducts get warmer. If there is a high resistance in either of the air temperature sensor circuits or the sensor itself, then the count value of the affected sensor would remain high.
  3. 13: This action ensures that the internal fan of the inside air temperature sensor assembly is providing air flow across the internal sensor.
  4. 17: Use the following table to determine that the recorded scan tool values are within range for the recorded probe temperatures.
Temperature °CTemperature °FScan Tool Display
0-432-40206-175 counts
5-941-49194-161 counts
10-1450-58180-145 counts
15-1959-67166-133 counts
20-2468-76150-119 counts
25-2977-85136-106 counts
30-3486-94121-93 counts
35-3995-103107-81 counts
40-44104-11294-69 counts
45-49113-12183-59 counts
50-54122-13072-51 counts
55-59131-13963-44 counts
60-64140-14855-37 counts

Too Cold in Vehicle (With HP2)

StepActionValuesYesNo
Schematic Reference: HVAC Schematics Connector End View Reference: HVAC Connector End Views DEFINITION: The temperature cannot be adjusted, or heating is insufficient.
1Did you perform the Diagnostic System Check - Vehicle?Go to Step 2Go to Diagnostic System Check - Vehicle
2IMPORTANT: If during this diagnostic procedure the HVAC control module is disconnected a recalibration of actuators must be performed to avoid misdiagnosis. Recalibrate actuators. Refer to Actuator Recalibration . Turn ON the ignition, with the engine OFF. Observe the Diagnostic Trouble Code (DTC) List - Vehicle . Does the scan tool display any DTC B0229, B0414, B0424 or B3770?Go to Diagnostic Trouble Code (DTC) List - VehicleGo to Step 3
3Turn ON the ignition, with the engine OFF. Turn ON the HVAC control module. Place the mode switch in the PANEL position. Place the blower motor switch in each speed position. Does the blower motor operate in any of the speed positions speed?Go to Step 4Go to Blower Motor Inoperative
4Does the blower motor operate in all desired speed positions?Go to Step 5Go to Blower Motor Malfunction
5Place the recirculation switch in the ON position. Observe the recirculation door. Place the recirculation switch in the OFF position. Does the recirculation door move from the recirculation position to the outside air position?Go to Step 6Go to Air Recirculation Malfunction
6Start the engine. Place the mode switch in PANEL position. Place the A/C request switch in the ON position. Observe the A/C compressor clutch. Place the A/C request switch in the OFF position. Does the A/C compressor clutch disengage?Go to Step 7Go to HVAC Compressor Clutch Does Not Disengage
7Start the engine. With a scan tool command the auxiliary coolant pump on. Does the auxiliary coolant pump operate?Go to Step 9Go to Step 8
8Test the auxiliary coolant pump power and ground circuits for an open, short to voltage or short to ground. Did you find and correct the condition?Go to Step 32Go to Step 27
9Perform the Heating Performance Diagnostic. Refer to Heating Performance Diagnostic . Did you find and correct the condition?Go to Step 32Go to Step 10
10Start the engine. Wait until engine coolant temperature reaches its normal operating temperature. Place the mode switch in the Floor position. Place the driver air temperature switch in the warmest position. With a scan tool, observe the right and left Heater Duct Actual and Heater Duct Desired parameters. Wait 3 minutes to allow the duct air temperature to stabilize. Do both of the Heater Duct Actual parameter values increase within 15 Counts of the Heater Duct Desired parameter?Go to Step 11Go to Step 22
11Place the mode switch in the Panel position. Place the driver air temperature switch in the warmest position. With a scan tool, observe the right and left AC Duct Actual and AC Duct Desired parameters. Wait 3 minutes to allow the duct air temperature to stabilize. Do both of the AC Duct Actual parameter values increase within 15 Counts of the AC Duct Desired parameter?Go to Step 12Go to Step 22
12Check the air temperature sensors for proper installation. Refer to the following procedures: Air Temperature Sensor Replacement - Upper Right Side Air Temperature Sensor Replacement - Upper Left Side Air Temperature Sensor Replacement - Lower Left Side Air Temperature Sensor Replacement - Lower Right Side Inside Air Temperature Sensor Assembly Replacement Did you find and correct the condition?Go to Step 32Go to Step 13
13Turn ON the ignition, with the engine OFF. Inspect for air flow through the inside air temperature sensor assembly by placing a 5 cm (2 in) square piece of paper over the inlet of the inside air temperature sensor assembly. Does the paper stay in place?Go to Step 15Go to Step 14
14Turn the ignition OFF. Disconnect the inside air temperature sensor assembly. Turn ON the ignition, with the engine OFF. Probe the inside air temperature sensor assembly control circuit of the inside air temperature sensor assembly with a test lamp that is connected to a good ground. Does the test lamp illuminate?Go to Step 20Go to Step 19
15Turn ON the ignition with the engine OFF. Install a scan tool. Cover the sunload sensor. With a scan tool, observe the Left Solar Sensor and Right Solar Sensor parameters in the Body Control Module data list. Does the scan tool indicate that the Left Solar Sensor and Right Solar Sensor parameters are greater than the specified value?220 CountsGo to Step 16Go to Step 25
16Place the temperature probe of the J 43600 near the inside air temperature sensor assembly. With a scan tool, observe the Inside Air Temp parameter in the Heating and Air Conditioning Data list. Does the scan tool indicate that the Inside Air Temp parameter is within 3°C (5°F) of the probe temperature?Go to Step 17Go to Step 21
17Start the engine. Place the blower motor switch in the minimum speed position. Allow the engine to reach normal operating temperature. Place the blower motor switch in the maximum speed position. Place the left and right air temperature switches in the FULL HOT positions. Place the mode switch in the bi-level position. Wait 3 minutes to allow the discharge air temperatures to stabilize. With a scan tool, record the values of the following parameters in the Heating and Air Conditioning data list: LH AC Duct Actual LH Heater Duct Actual RH AC Duct Actual RH Heater Duct Actual With the temperature probes of the J 43600 , record the air temperatures near the following sensors: The left upper air temperature sensor The left lower air temperature sensor The right upper air temperature sensor The right lower air temperature sensor Are the parameter values within the specified range for the recorded air temperatures?Go to Diagnostic AidsGo to Step 18
18Turn OFF the ignition. Disconnect the suspect air temperature sensor. Place the temperature probe of the J 43600 near the air temperature sensor. Record the probe temperature. Measure the resistance of the air temperature sensor. Refer to the Sensor Resistance Table (Primary HVAC) . Does the resistance measure near the specified range?Go to Step 26Go to Step 22
19Test the inside air temperature sensor assembly control circuit of the inside air temperature sensor assembly for an open, a high resistance, or a short to ground. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition?Go to Step 32Go to Step 26
20Test the ground circuit of the inside air temperature sensor assembly for an open or high resistance. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the conditionGo to Step 32Go to Step 24
21Turn OFF the ignition. Disconnect the inside air temperature assembly. Place the temperature probe of the J 43600 near the inside air temperature sensor assembly. Record the probe temperature. Measure the resistance of the inside air temperature sensor. Refer to the Sensor Resistance Table (Primary HVAC) . Does the resistance measure within the specified range ?Go to Step 26Go to Step 22
22Test the signal circuit of the suspect air temperature sensor for a high resistance. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition?Go to Step 32Go to Step 23
23Test the low reference circuit of the suspect air temperature sensor for a high resistance. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition?Go to Step 32Go to Step 24
24Inspect for poor connections at the harness connector of the suspect air temperature sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition?Go to Step 32Go to Step 29
25Inspect for poor connections at the harness connector of the sunload sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition?Go to Step 32Go to Step 30
26Inspect for poor connections at the harness connector of the HVAC control module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition?Go to Step 32Go to Step 31
27Inspect for poor connections at the harness connector of the auxiliary coolant pump. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition?Go to Step 32Go to Step 28
28Replace the auxiliary coolant pump. Refer to Auxiliary Water Pump Replacement . Did you complete the replacement?Go to Step 32
29Replace the suspect air temperature sensor. Refer to one of the following procedures: Air Temperature Sensor Replacement - Upper Right Side Air Temperature Sensor Replacement - Upper Left Side Air Temperature Sensor Replacement - Lower Left Side Air Temperature Sensor Replacement - Lower Right Side Inside Air Temperature Sensor Assembly Replacement Did you complete the replacement?Go to Step 32
30Replace the sunload sensor. Refer to Sun Load Sensor Replacement . Did you complete the replacement?Go to Step 32
31Replace the HVAC control module. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement?Go to Step 32
32Operate the system in order to verify the repair. Did you correct the condition?System OKGo to Step 2
IMPORTANT
If during this diagnostic procedure the HVAC control module is disconnected a recalibration of actuators must be performed to avoid misdiagnosis.

Too Cold in Vehicle (With HP2)

The numbers below refer to the step numbers in the diagnostic table.

  1. 8: This step ensures that the lower air temperature sensors operate properly. The LH and RH Heater Duct Actual parameter count values should lower as the air temperature of the ducts get warmer. If there is a high resistance in either of the air temperature sensors circuits or the sensor itself then the count value of the effected sensor would remain high.
  2. 9: This step ensures that the upper air temperature sensors operate properly. The LH and RH AC Duct Actual parameter count values should lower as the air temperature of the ducts get warmer. If there is a high resistance in either of the air temperature sensors circuits or the sensor itself then the count value of the effected sensor would remain high.
  3. 11: This action ensures that the internal fan of the inside air temperature sensor assembly is providing air flow across the internal sensor.
  4. 15: Use the following table to determine that the recorded scan tool values are within range for the recorded probe temperatures.
Temperature °CTemperature °FScan Tool Display
0-432-40206-175 counts
5-941-49194-161 counts
10-1450-58180-145 counts
15-1959-67166-133 counts
20-2468-76150-119 counts
25-2977-85136-106 counts
30-3486-94121-93 counts
35-3995-103107-81 counts
40-44104-11294-69 counts
45-49113-12183-59 counts
50-54122-13072-51 counts
55-59131-13963-44 counts
60-64140-14855-37 counts

Too Cold in Vehicle (With Out HP2)

StepActionValuesYesNo
Schematic Reference: HVAC Schematics Connector End View Reference: HVAC Connector End Views DEFINITION: The temperature can not be adjusted, or heating is insufficient.
1Did you perform the Diagnostic System Check - Vehicle?Go to Step 2Go to Diagnostic System Check - Vehicle
2IMPORTANT: If during this diagnostic procedure the HVAC control module is disconnected a recalibration of actuators must be performed to avoid misdiagnosis. Recalibrate actuators. Refer to Actuator Recalibration . Turn ON the ignition, with the engine OFF. Observe the Diagnostic Trouble Code (DTC) List - Vehicle . Does the scan tool display any DTC B0229, B0414, B0424 or B3770?Go to Diagnostic Trouble Code (DTC) List - VehicleGo to Step 3
3Turn ON the ignition, with the engine OFF. Turn ON the HVAC control module. Place the mode switch in the PANEL position. Place the blower motor switch in each speed position. Does the blower motor operate in any of the speed positions speed?Go to Step 4Go to Blower Motor Inoperative
4Does the blower motor operate in all desired speed positions?Go to Step 5Go to Blower Motor Malfunction
5Place the recirculation switch in the ON position. Observe the recirculation door. Place the recirculation switch in the OFF position. Does the recirculation door move from the recirculation position to the outside air position?Go to Step 6Go to Air Recirculation Malfunction
6Start the engine. Place the mode switch in PANEL position. Place the A/C request switch in the ON position. Observe the A/C compressor clutch. Place the A/C request switch in the OFF position. Does the A/C compressor clutch disengage?Go to Step 7Go to HVAC Compressor Clutch Does Not Disengage
7Perform the Heating Performance Diagnostic. Refer to Heating Performance Diagnostic . Did you find and correct the condition?Go to Step 28Go to Step 8
8Start the engine. Wait until engine coolant temperature reaches its normal operating temperature. Place the mode switch to the Floor position. Place the drivers air temperature switch to the warmest position. With a scan tool, observe the right and left Heater Duct Actual and Heater Duct Desired parameters. Wait 3 minutes to allow the duct air temperature to stabilize. Do both of the Heater Duct Actual parameter values increase within 15 Counts of the Heater Duct Desired parameter?Go to Step 9Go to Step 20
9Place the mode switch to the Panel position. Place the drivers air temperature switch to the warmest position. With a scan tool, observe the right and left AC Duct Actual and AC Duct Desired parameters. Wait 3 minutes to allow the duct air temperature to stabilize. Do both of the AC Duct Actual parameter values increase within 15 Counts of the AC Duct Desired parameter?Go to Step 10Go to Step 20
10Check the air temperature sensors for proper installation. Refer to the following procedures: Air Temperature Sensor Replacement - Upper Right Side Air Temperature Sensor Replacement - Upper Left Side Air Temperature Sensor Replacement - Lower Left Side Air Temperature Sensor Replacement - Lower Right Side Inside Air Temperature Sensor Assembly Replacement Did you find and correct the condition?Go to Step 28Go to Step 11
11Turn ON the ignition, with the engine OFF. Inspect for air flow through the inside air temperature sensor assembly by placing a 5 cm (2 in) square piece of paper over inlet of the inside air temperature sensor assembly. Does the paper stay in place?Go to Step 13Go to Step 12
12Turn the ignition OFF. Disconnect the inside air temperature sensor assembly. Turn ON the ignition, with the engine OFF. Probe the inside air temperature sensor assembly control circuit of the inside air temperature sensor assembly with a test lamp that is connected to a good ground. Does the test lamp illuminate?Go to Step 18Go to Step 17
13Turn ON the ignition with the engine OFF. Install a scan tool. Cover the sunload sensor. With a scan tool, observe the Left Solar Sensor and Right Solar Sensor parameters in the Body Control Module data list. Does the scan tool indicate that the Left Solar Sensor and Right Solar Sensor parameters are greater than the specified value?220 CountsGo to Step 14Go to Step 23
14Place the temperature probe of the J 43600 ACR 200 Air Conditioning Service Center near the inside air temperature sensor assembly. With a scan tool, observe the Inside Air Temp parameter in the Heating and Air Conditioning Data list. Does the scan tool indicate that the Inside Air Temp parameter is within 3°C (5°F) of the probe temperature?Go to Step 15Go to Step 19
15Start the engine. Place the blower motor switch in the minimum speed position. Allow the engine to reach normal operating temperature. Place the blower motor switch in the maximum speed position. Place the left and right air temperature switches in the FULL HOT positions. Place the mode switch in the bi-level position. Wait 3 minutes to allow the discharge air temperatures to stabilize. With a scan tool, record the values of the following parameters in the Heating and Air Conditioning data list: LH AC Duct Actual LH Heater Duct Actual RH AC Duct Actual RH Heater Duct Actual With the temperature probes of the J 43600 , record the air temperatures near the following sensors: The left upper air temperature sensor The left lower air temperature sensor The right upper air temperature sensor The right lower air temperature sensor Are the parameter values within the specified range for the recorded air temperatures?Go to Diagnostic AidsGo to Step 16
16Turn OFF the ignition. Disconnect the suspect air temperature sensor. Place the temperature probe of the J 43600 near the air temperature sensor. Record the probe temperature. Measure the resistance of the air temperature sensor. Refer to the Sensor Resistance Table (Primary HVAC) . Does the resistance measure near the specified range?Go to Step 24Go to Step 20
17Test the inside air temperature sensor assembly control circuit of the inside air temperature sensor assembly for an open, a high resistance, or a short to ground. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition?Go to Step 28Go to Step 24
18Test the ground circuit of the inside air temperature sensor assembly for an open or high resistance. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition?Go to Step 28Go to Step 22
19Turn OFF the ignition. Disconnect the inside air temperature assembly. Place the temperature probe of the J 43600 near the inside air temperature sensor assembly. Record the probe temperature. Measure the resistance of the inside air temperature sensor. Refer to the Sensor Resistance Table (Primary HVAC) . Does the resistance measure within the specified range ?Go to Step 24Go to Step 20
20Test the signal circuit of the suspect air temperature sensor for a high resistance. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition?Go to Step 28Go to Step 21
21Test the low reference circuit of the suspect air temperature sensor for a high resistance. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition?Go to Step 28Go to Step 22
22Inspect for poor connections at the harness connector of the suspect air temperature sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition?Go to Step 28Go to Step 25
23Inspect for poor connections at the harness connector of the sunload sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition?Go to Step 28Go to Step 26
24Inspect for poor connections at the harness connector of the HVAC control module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition?Go to Step 28Go to Step 27
25Replace the suspect air temperature sensor. Refer to one of the following procedures: Air Temperature Sensor Replacement - Upper Right Side Air Temperature Sensor Replacement - Upper Left Side Air Temperature Sensor Replacement - Lower Left Side Air Temperature Sensor Replacement - Lower Right Side Inside Air Temperature Sensor Assembly Replacement Did you complete the replacement?Go to Step 28
26Replace the sunload sensor. Refer to Sun Load Sensor Replacement . Did you complete the replacement?Go to Step 28
27Replace the HVAC control module. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement?Go to Step 28
28Operate the system in order to verify the repair. Did you correct the condition?System OKGo to Step 2
IMPORTANT
If during this diagnostic procedure the HVAC control module is disconnected a recalibration of actuators must be performed to avoid misdiagnosis.

Too Cold in Vehicle (With Out HP2)

Air Delivery Description and Operation

The air delivery description and operation is divided into 5 areas

  1. HVAC Control Components
  2. Air Speed
  3. Air Delivery
  4. Recirculation Operation
  5. Automatic Operation

Recirculation Operation

The HVAC control module controls the air intake through the recirculation actuator. The recirculation switch closes the recirculation door in order to circulate the air within the vehicle. The outside air switch opens the recirculation door in order to route outside air into the vehicle. Regardless of the blower motor switch position, recirculation is available only in the panel and bi-level mode switch positions. Including the OFF position. The mode switch must be placed in either the panel or bi-level position before the blower motor switch is placed in the OFF position. In order to reduce windshield fogging, outside air is circulated when the mode switch is in the defrost or defog positions. If the recirculation switch is pressed into the ON position when the mode switch is in an unavailable mode position, then the recirculation switch LED will flash 3 times. If the HVAC control module detects a fault with the recirc door the HVAC control module will try to drive the actuator for a predetermined amount of time, to outside air, which is the defaulted position for the recirculation actuator.

Automatic Operation

In automatic operation, the HVAC control module will maintain the comfort level inside of the vehicle by controlling the A/C compressor clutch, the blower motor, the air temperature actuators, mode actuator and recirculation.

To place the HVAC system in Automatic mode, the following is required

  1. The Auto switch must be activated.
  2. The air temperature switch must be in any other position other than full hot or full cold position.

Once the desired temperature is reached, the blower motor, mode, recirculation and temperature actuators will automatically be adjusted to maintain the temperature selected. The HVAC control module performs the following functions to maintain the desired air temperature

  1. Monitor the following sensors: Inside air temperature sensor Ambient Air Temperature Sensor Lower Left Air Temperature Sensor Lower Right Air Temperature Sensor Upper Left Air Temperature Sensor Upper Right Air Temperature Sensor
  2. Regulate blower motor speed
  3. Position the air temperature actuator
  4. Position the mode actuator
  5. Position the recirculation actuator
  6. Request A/C operation

Air Temperature Description and Operation

The air temperature controls are divided into 5 areas

  1. HVAC Control Components
  2. Heating and A/C Operation
  3. Automatic Operation
  4. Engine Coolant
  5. A/C Cycle

Heating and A/C Operation

The purpose of the heating and A/C system is to provide heated and cooled air to the interior of the vehicle. The A/C system will also remove humidity from the interior and reduce windshield fogging. The vehicle operator can determine the passenger compartment temperature by adjusting the air temperature switch. The vehicle passenger can offset the passenger temperature as much as 16.7°C (30°F). Regardless of the temperature setting, the following can effect the rate that the HVAC system can achieve the desired temperature

  1. Recirculation actuator setting
  2. Difference between inside and desired temperature
  3. Difference between ambient and desired temperature
  4. Blower motor speed setting
  5. Mode setting

The control module makes the following actions when automatic operation is not selected, and an air temperature setting is selected

  1. When the air temperature switch is placed in the warmest position, the control module commands the air temperature door to divert maximum air past the heater core.
  2. When the air temperature switch is placed in the coldest position, the control module commands the air temperature door to direct air to bypass the heater core.
  3. When the air temperature switch is placed between the warmest and coldest positions, the control module monitors the following sensor inputs to determine the air temperature door position that diverts the appropriate amount of air past the heater core in order to achieve the desired temperature: Sunload Duct temperatures Ambient temperature Inside temperature

The A/C system can be engaged by either pressing the A/C switch or during automatic operation. The HVAC control module sends a class 2 message to the PCM for A/C compressor engagement. The PCM will provide a ground for the A/C compressor relay enabling it to close its internal contacts to send battery voltage to the A/C compressor clutch coil. The A/C compressor diode will prevent a voltage spike, resulting from the collapse of the magnetic field of the coil, from entering the vehicle electrical system when the compressor is disengaged.

The following conditions must be met in order for the A/C compressor clutch to turn on

  1. The ambient air temperature is above 4°C (40°F).
  2. The A/C low pressure switch signal circuit is grounded.
  3. The A/C refrigerant pressure sensor parameter is less than 2957 kPa (429 psi).
  4. The PCM receives an A/C request from the HVAC control module.
  5. The engine coolant temperature (ECT) is less than 121°C (250°F).
  6. The engine RPM is more than 550 RPM.
  7. The throttle position is less than 100%.

The HVAC control module monitors the A/C low pressure switch signal circuit. If the voltage signal on this circuit has no voltage drop the module will interpret this condition as a low pressure, disabling the A/C request. The A/C low pressure switch will open its internal contacts at 151 kPa (22 psi). Then close the contacts at 275 kPa (40 psi) to resume A/C operation. This switch assists in cycling the A/C compressor and prevents A/C compressor operation if system has a low refrigerant level.

The PCM monitors the A/C refrigerant pressure sensor signal circuit. The voltage signal on this circuit is proportional to the refrigerant pressure inside the A/C high side pressure line. As the pressure inside the line increases, so does the voltage signal. If the pressure is above 2957 kPa (429 psi), the A/C compressor output is disabled. When the pressure lowers to 1578 kPa (229 psi), the PCM enables the compressor to operate.

The sensor information is used by the PCM to determine the following

  1. The A/C high side pressure
  2. An A/C system load on the engine
  3. An excessive A/C high side pressure
  4. The heat load at the A/C condenser

Once engaged, the compressor clutch will be disengaged for the following conditions

  1. The ambient air temperature is less than 4°C (40°F).
  2. The throttle position is 100%.
  3. The A/C low pressure switch is open.
  4. The A/C high side pressure is more than 2957 kPa (429 psi).
  5. The A/C low side pressure is less than 151 kPa (22 psi).
  6. The engine coolant temperature (ECT) is more than 121°C (250°F).
  7. The engine speed is more than 5500 RPM.
  8. Transmission shift
  9. The PCM detects excessive torque load.
  10. The PCM detects insufficient idle quality.
  11. The PCM detects a hard launch condition.

In automatic operation, the HVAC control module will maintain the comfort level inside of the vehicle by controlling the A/C compressor clutch, the blower motor, the air temperature actuators, mode actuator and recirculation.

To place the HVAC system in Automatic mode, the following is required

  1. The Auto switch must be activated
  2. The air temperature switch must be in any other position other than full hot or full cold position

Once the desired temperature is reached, the blower motor, mode, recirculation and temperature actuators will automatically be adjusted to maintain the temperature selected. The HVAC control module performs the following functions to maintain the desired air temperature

  1. Monitor the following sensors: Inside Air Temperature Sensor Ambient Air Temperature Sensor Lower Left Air Temperature Sensor Lower Right Air Temperature Sensor Upper Left Air Temperature Sensor Upper Right Air Temperature Sensor
  2. Regulate blower motor speed
  3. Position the air temperature actuator
  4. Position the mode actuator
  5. Position the recirculation actuator
  6. Request A/C operation

More articles — HVAC System - Automatic