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 concerns that can be readily identified, repair as necessary.

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 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 from the PCM or EATC.

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

If the EATC DTCs retrieved are related to the concern, go to the EATC 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). Diagnostic Trouble Code Tests and Associated Procedures

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

Electronic Automatic Temperature Control Module - Diagnostic Methods
The EATC system must be diagnosed by first retrieving any DTCs, if present.
- An on-demand (hard fault) DTC indicates that the fault is currently present. An on-demand DTC suggests a wiring fault, disconnected connector or component failure.
- A continuous (intermittent) DTC alone (corresponding on-demand DTC is not present) indicates that the fault is an intermittent condition and may not be currently present. A continuous only DTC suggests a poor wiring connection, loose pin or terminal or intermittent component failure.

On-demand (hard fault) or continuous (intermittent fault) DTCs can be retrieved using a scan tool. If using a scan tool, refer to the scan tool operating manual.

On-demand DTCs can also be retrieved by carrying out the Electronic Automatic Temperature Control Module On-Demand Self Test. To retrieve and/or clear continuous DTCs, carry out the Electronic Automatic Temperature Control Module - Retrieve Continuous DTCs procedure. Always carry out the Electronic Automatic Temperature Control Module On-Demand Self Test before retrieving continuous DTCs. Without Scan Tool With Manufacturer's Scan Tool

If no DTCs are present, GO to Symptom Chart for the appropriate diagnostic action. Symptom Related Diagnostic Procedures

Electronic Automatic Temperature Control (EATC) Module and Electronic Manual Temperature Control (EMTC) Module Cold Boot Process
The purpose of the cold boot process is to allow the EATC or EMTC module to reinitialize 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 or EMTC module electrical connectors.
3. Wait on minute.
4. Connect the EATC or EMTC module electrical connectors.
5. Turn the ignition switch to the ON position.
6. Select any position except OFF on the EATC or EMTC module.

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