Reading and Clearing Diagnostic Trouble Codes

Electronic Climate Control (ECC) Panel:

Fuel Data Center:

Diagnostic Flow Diagram - Part 1 Of 3:

ON-BOARD DIAGNOSTICS SYSTEM OPERATION

This vehicle is equipped with an extensive on-board diagnostic system which is capable of detecting and compensating for faults, alerting the operator of a fault and recording pertinent data during the failure. It is also capable of displaying information about current vehicle performance when a fault occurred.

In order to access and control the self diagnostics features available, additional electronic components are utilized by the service technician. The Electronic Climate Control (ECC) and the Fuel Data Center (FDC) provide displays and keyboard switches.

The display and keyboard information is transmitted over a single wire data circuit which carries the coded data messages back and forth between the different control computers. and the display panels (ECC/FDC). This communications process allows the appropriate computer to transfer any of its available diagnostic information to the appropriate panel for display during service. By depressing appropriate buttons on the ECC, data messages are requested to be displayed on the FDC. the diagnostics mode, the mode indicators on the Electronic Climate Control (ECC) are used to indicate system operating modes. The different modes of operation are indicated by the status indicator either being turned "ON" or turned "OFF".


NOTE: For the purpose of the test, the diagnostic procedures may refer to the Powertrain Control Module (PCM) as the ECM or Engine Control Module.


OPERATING ON-BOARD DIAGNOSTIC SYSTEM


To enter diagnostic mode, proceed as follows:

1. Turn ignition "ON".

2. Depress the "OFF" and "WARMER" buttons on the Electronic Climate Control (ECC) simultaneously and hold until the segment check appears on the Fuel Data Center (FDC).


SEGMENT CHECK

The purpose of illuminating the panels is to check that all segments of the LED displays are working. The turn signal indicators DO NOT light during this check. If any of the segments are inoperative, the affected display panel will need to be diagnosed.


SYSTEM READY - CODE .7.0

Code .7.0 is used as a decision point in the diagnostic sequence. When Code .7.0 is displayed on the display, the technician may select the diagnostic features that he wants to perform. This is the hub of the diagnostic routines. Follow the appropriate procedure to return to this point after an action is performed.


TROUBLE CODE DISPLAY

After the segment check, any trouble code stored in computer memory will be displayed on the "Fuel Data Center." Display of the trouble codes will begin with an "8.8.8" for one second. A "..E" will then be displayed for PCM/ECM HISTORY codes (if any exist), then a ".E.E" for PCM/ECM HARD codes. After the PCM/ECM codes display the BCM codes are displayed with the following prefix; "..F" for BCM HISTORY codes, and a ".F.F" for BCM HARD codes. After all codes have been displayed or if no trouble codes are stored, ".7.0" will appear on the "Data Center" display.




STATUS LIGHTS

While in diagnostics, the displays on the ECC may be used to indicate the status of various inputs and operating conditions. The meaning of each word or symbol on the panel will change depending on whether the BCM or PCM system level is selected.



EXITING DIAGNOSTIC MODE

To get out of the diagnostic mode, depress the "AUTO" button or turn the ignition switch "OFF" for 10 seconds. The temperature setting will reappear in the display panel. Trouble codes are not erased when this is done.