Diagnostic Test

CHECK FOR AN ACTIVE DTC
1. With the scan tool, read HVAC DTCs and record on the repair order.
2. Record the Environmental Data.
3. With the scan tool, erase DTCs.
4. Using the recorded Environmental Data, along with the When Monitored and Set Conditions above, operate the vehicle in the conditions that set the DTC.
5. With the scan tool, read HVAC DTCs.
  Did the DTC return?
  
  Yes
  - Go To 2
  No
  - Perform the INTERMITTENT CONDITIONS TEST. Refer to STANDARD PROCEDURE .
CHECK THE A/C HEATER CONTROL PANEL HARNESS CONNECTOR FOR DAMAGE
1. Check for loose, damaged or corroded terminals on the A/C Heater Control panel harness connector and the HVAC Module harness connector.
  Are the harness connectors damaged?
  
  Yes
  - Repair the harness connectors as necessary.
  - Perform the HVAC VERIFICATION TEST. Refer to STANDARD PROCEDURE .
  No
  - Go to Step 3.
CHECK THE (D409) LIN BUS CIRCUIT FOR AN OPEN/HIGH RESISTANCE
1. Turn the Ignition off.
2. Disconnect the HVAC Module harness connector.
3. Disconnect the A/C Heater Control Panel harness connector.
4. Using a multimeter, check the resistance in the (D409) LIN BUS circuit between pin3 of the A/C Heater Control Panel harness connector and pin 12 of the HVAC Module harness connector.
  Is the resistance above 3 Ohms?
  
  Yes
  - Repair the (D409) LIN BUS circuit for an open circuit or high resistance.
  - Perform the HVAC VERIFICATION TEST. Refer to STANDARD PROCEDURE .
  No
  - Go to Step 4.
CHECK THE (D409) LIN BUS CIRCUIT FOR A SHORT
1. Check for a short circuit in the in the (D409) LIN BUS circuit between pin3 of the A/C Heater Control Panel harness connector and pin 12 of the HVAC Module harness connector.
  Is there a short circuit in the (D409) LIN BUS circuit?
  
  Yes
  - Repair the (D409) LIN BUS circuit for a short circuit.
  - Perform the HVAC VERIFICATION TEST. Refer to STANDARD PROCEDURE .
  No
  - Go to Step 5.
CHECK THE A/C HEATER CONTROL PANEL FOR PROPER OPERATION
1. Check the A/C Heater Control Panel for proper operation of all control dials and switches.
  Is the A/C Heater Control Panel operating correctly?
  
  Yes
  - Go To 6
  No
  - Replace the A/C Heater Control Panel in accordance with the service information.
    Refer to CONTROL, A/C AND HEATER, REMOVAL AND INSTALLATION .
  - Perform the HVAC VERIFICATION TEST. Refer to STANDARD PROCEDURE .
CHECK RELATED HARNESS CONNECTIONS
1. Disconnect all HVAC Module harness connectors.
2. Disconnect all related in-line harness connections (if equipped).
3. Disconnect the related component harness connectors.
4. Inspect harness connectors, component connectors, and all male and female terminals for the following conditions:
  - Proper connector installation.
  - Damaged connector locks.
  - Corrosion.
  - Other signs of water intrusion.
  - Weather seal damage (if equipped).
  - Bent terminals.
  - Overheating due to a poor connection (terminal may be discolored due to excessive current draw).
  - Terminals that have been pushed back into the connector cavity.
  - Perform a terminal drag test on each connector terminal to verify proper terminal tension.
  Repair any conditions that are found.
5. Reconnect all HVAC Module harness connectors. Be certain that all harness connectors are fully seated and the connector locks are fully engaged.
6. Reconnect all in-line harness connectors (if equipped). Be certain that all connectors are fully seated and the connector locks are fully engaged.
7. Reconnect all related component harness connectors. Be certain that all connectors are fully seated and the connector locks are fully engaged.
8. With the scan tool, erase DTCs.
9. Using the recorded Environmental Data, along with the When Monitored and Set Conditions above, operate the vehicle in the conditions that set the DTC.
10. With the scan tool, read HVAC Module DTCs.
  Did the DTC return?
  
  Yes
  - Replace the HVAC Module in accordance with the Service information. Refer to MODULE, HVAC, REMOVAL AND INSTALLATION .
  - Perform the HVAC VERIFICATION TEST. Refer to STANDARD PROCEDURE .
  No
  - Repair any faulty connections.
  - Perform the HVAC VERIFICATION TEST. Refer to STANDARD PROCEDURE .