B108F

B108F-AUTOMATIC TEMPERATURE CONTROL SYSTEM PERFORMANCE

For a complete wiring diagram, refer to the Wiring Information Electrical Diagrams.

Theory of Operation

The A/C Heater Control monitors BUS communication for input information from the Powertrain Control Module (PCM) for engine coolant, ambient temperature and vehicle speed, and the Electronic Overhead Module (EOM) for Infrared Sensor data. This data is used in conjunction with other inputs to optimize HVAC operation.

- When Monitored:
With the ignition on.

- Set Condition:
If the A/C Heater Control either fails to receive Engine Coolant Temperature Sensor, Ambient Temperature Sensor, Vehicle speed or Infrared Sensor data, or if the data from any of these sensors is out of range. This DTC has a maturing time of five seconds and a de-maturing time of 10 seconds. If the DTCs status changes from active to stored it will stay in memory for 100 ignition cycles.





Always perform the HVAC Pre-Diagnostic Troubleshooting procedure before proceeding. Initial Inspection and Diagnostic Overview.

1. VERIFY THAT THE DTC IS ACTIVE
1. With the scan tool, read HVAC DTCs.

Is this DTC active?

Yes

- Go To 2

No

- Go To 5

2. CHECK FOR ACTIVE DTC U0019-CAN B BUS CIRCUIT
1. With the scan tool, read HVAC DTCs.

Is the DTC U0019-CAN B BUS CIRCUIT present?

Yes

- U0019 Perform the appropriate diagnostic procedure.

No

- Go To 3

3. VERIFY THAT THE PCM, FCM, AND EOM ARE ACTIVE ON THE BUS
1. Turn the ignition on.
2. With the scan tool, select ECU View.
3. Verify that the PCM, EOM and FCM, are active on the bus.

Are all of these modules active on the bus?

Yes

- Go To 4

No

- Manufacturer Code Charts for No Response diagnostic procedures.
- Perform the HVAC VERIFICATION TEST. HVAC Verification Test.

4. CHECK FOR DTCs IN THE PCM, FCM, AND EOM
1. With the scan tool, select ECU View.
2. Check for DTCs in the PCM, FCM, and EOM.

Are there any DTCs present in any of these modules?

Yes

- Refer to Based Diagnostics and perform the appropriate diagnostic procedure(s). If PCM DTCs are present, perform its respective test first.
- Perform the HVAC VERIFICATION TEST. HVAC Verification Test.

No

- Replace the A/C Heater Control.
- Perform the HVAC VERIFICATION TEST. HVAC Verification Test.

5. CHECK THE WIRING AND CONNECTORS
1. The conditions necessary to set the DTC are not present at this time.
2. With the scan tool, check the Environmental Data to help identify the conditions in which the DTC was set.
3. Using the schematics as a guide, inspect the wiring and connectors specific to this circuit.
4. Check for an intermittent condition by inspecting the related wiring harness for chafed, pierced, pinched, or partially broken wires.
5. Check the connectors for broken, bent, pushed out, spread, corroded, or contaminated terminals.
6. Wiggle the wiring and connectors while checking for shorted and open circuits.

Were there any problems found?

Yes

- Repair as necessary.
- Perform the HVAC VERIFICATION TEST. HVAC Verification Test.

No

- Test complete.