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Home >> Cadillac >> 1994 >> DeVille V8-4.9L VIN B >> Repair and Diagnosis >> Powertrain Management >> Computers and Control Systems >> Testing and Inspection >> Reading and Clearing Diagnostic Trouble Codes >> Accessing and Reading Diagnostic Trouble Codes >> Operating Self-Diagnostic Feature

Operating Self-Diagnostic Feature


OPERATING SELF-DIAGNOSTIC SYSTEM
This section explains the mechanics of operating the self-diagnostic system. It may be helpful to refer to Figure 8D-3 while reviewing this
material.






HOW TO ENTER DIAGNOSTICS
To enter diagnostics, proceed as follows:
1. Turn the ignition "ON".
2. Push the "OFF" and "WARM" buttons on the CCC simultaneously and hold until the segment check appears on the IPC.

NOTICE: Operating the vehicle in diagnostics for extended time periods without the engine running or without a battery charger will cause the battery to run down and possibly relate false diagnostic information, or cause a no start condition. To ensure proper operation, attach a battery charger, if vehicle is to be operated in diagnostics without engine running for periods longer than 1/2 hour.

SEGMENT CHECK
The purpose of illuminating the IPC is verify all segments of the LED displays are working. The turn signal indicators do not light during this check. Further diagnosis should not be attempted unless all segments appear, as this could lead to misdiagnosis. If any portions or segments of the IPC displays are inoperative, the IPC must be replaced.

TROUBLE CODE DISPLAY
After diagnostics is entered, any trouble codes stored in computer memory will be displayed. Codes may be stored for the PCM, IPC, AC, DERM, TCS or RSS systems.
Each trouble code consists of the system abbreviation (P - Engine (PCM), I - IPC, A - AC, R - SIR, T - TCS, or S - RSS), a three digit code identifier, and the letter C or H. All codes for each system are displayed together, in the order of their three digit number (lowest first - i.e. E013, EO14, etc.). The final digit of the code, a "C" or an "H" is used to indicate whether the code is current or history. "C" means the fault was still present the last time the diagnostic test was run, while "H" means the failure was not present the last time the code was tested for.
If no codes are present for a system, a "NO X CODE" message (with X being the system i.e. E, I, A, R, T or S) will be displayed. If the communication line to a component Is not operating, a "NO X DATA" message will be displayed, indicating that the IPC could not communicate with that system.
At any time during the display of trouble codes, if the "AUTO" button on the IPC is depressed the system will exit "Service Mode" and go back to normal vehicle operation.

STATUS LIGHTS
While in diagnostics, the displays on the CCC 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 ACP or PCM system level is selected. This is detailed in the sections covering these systems.

SELECTING THE SYSTEM
After trouble codes have been displayed, a specific vehicle system (PCM, IPC, AC, SIR, TCS, or RSS) may be selected for testing.
The first available system will be automatically displayed (i.e. PCM). While selecting the system to test, any of the following actions may be taken:
1. Depressing the "HI" button on the CCC will select the displayed system for testing.
2. Depressing the "LO" button on the CCC will display the next available system selection. This allows the display to be stepped through all system choices. This list of systems can be repeated following the end of the system list.
3. Depressing the "OFF" button the CCC will stop the system selection process and return the display to the beginning of the trouble code sequence.

SELECTING THE TEST TYPE
Having selected a system, the first available test type will be displayed (i.e. PCM DATA). While selecting a specific test type, any of the following actions may be taken:
1. Depressing the "HI" button on the CCC will select the displayed test type. At this point the first of several specific tests will appear.
2. Depressing the "LO" button on the CCC will display the next available test type for the selected system. This allows the display to be stepped through all available test type choices. This list of test types can be repeated following the display of the last test type.
3. Depressing the "OFF" button on the CCC will stop the test type selection process and return the display to the next available system selection.
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