Initial Inspection and Diagnostic Overview

INSPECTION AND VERIFICATION

1. Verify the customer's concern by operating the climate control system to duplicate the condition.

Visual Inspection Chart:

2. Inspect to determine if one of the mechanical or electrical concerns apply:
3. As pinpoint tests and measurements are being carried out, be sure to inspect for any disconnected, loose-fitting or incorrectly installed component, module and in-line electrical connectors and pins.
4. If the inspection reveals obvious concern(s) that can be readily identified, repair as required.

5. NOTE: Make sure to use the latest scan tool software release.

If the cause is not visually evident, connect the scan tool to the data link connector (DLC).

6. NOTE: The vehicle communication module (VCM) LED prove-out confirms power and ground from the DLC are provided to the VCM.

If the scan tool does not communicate with the VCM:
- check the VCM connection to the vehicle.
- check the scan tool connection to the VCM.
- refer to Information Bus (Module Communications Network), No power to the scan tool, to diagnose no communication with the scan tool.

7. If the scan tool does not communicate with the vehicle:
- verify the ignition key is in the ON position.
- verify the scan tool operation with a known good vehicle.
- refer to Information Bus (Module Communications Network) to diagnose no response from the rear redundant control module (RRCM), powertrain control module (PCM) or electronic automatic temperature control (EATC) module.

8. Carry out the network test.
- If the scan tool responds with no communication from one or more modules, refer to Information Bus (Module Communications Network).
- If the network test passes, retrieve and record the continuous memory diagnostic trouble codes (DTCs).

9. Clear the continuous DTCs and carry out the self-test diagnostics for the RRCM, PCM or EATC.

10. NOTE: Some PCM DTCs may inhibit air condition (A/C) operation. If any PCM DTCs are retrieved, diagnose those first. REFER to Computers and Control Systems.

If the RRCM DTCs retrieved are related to the concern, go the Rear Redundant Control Module (RRCM) Diagnostic Trouble Code (DTC) Index. If the EATC DTCs retrieved are related to the concern, go to the Electronic Automatic Temperature Control (EATC) Module Diagnostic Trouble Code (DTC) Index. If the PCM DTCs retrieved are related to the concern, go to Computers and Control Systems. For all other DTCs, refer to Body Control Systems (Multifunction Electronic Control Module). Rear Redundant Control Module (RRCM) Diagnostic Trouble Code (DTC) Index Electronic Automatic Temperature Control (EATC) Module Diagnostic Trouble Code (DTC) Index

11. If no DTCs related to the concern are retrieved, GO to Symptom Chart. Symptom Related Diagnostic Procedures

ELECTRONIC AUTOMATIC TEMPERATURE CONTROL MODULE - DISPLAY CONTINUOUS CODES

- This function will display continuous (intermittent) codes and hard faults that occur during normal operation.
- To display continuous codes, press the OFF and FLOOR buttons simultaneously and then release and within 2 seconds press the RECIRC button.
- To exit the display of continuous codes, press the FRONT DEFROST button. This will exit and clear all DTCs. Press any button except DEFROST to exit without clearing DTCs set before the last ignition cycle.
- Always exit continuous codes display before powering the system down (system turned off).
- Continuous DTCs are saved only after an ignition cycle.
- Continuous DTCs will be deleted after 80 ignition switch ON cycles after the intermittent condition occurs.

Electronic Automatic Temperature Control (EATC) Module Cold Boot Process
The purpose of the cold boot process is to allow the EATC module to re-initialize and calibrate the actuators. To carry out the cold boot process, follow the steps below.
1. Turn the ignition switch to the OFF position.
2. Disconnect the EATC module electrical connectors.
3. Wait one minute.
4. Connect the EATC module electrical connectors.
5. Turn the ignition switch to the ON position
6. Select any position except OFF on the EATC module.

The EATC module will not initialize and calibrate the actuators. Calibration of the actuators will take approximately 30 seconds.