Accessing and Reading Diagnostic Trouble Codes

Diagnostic Display:

NOTE: For referrals to any chart not included in DIAGNOSTIC CHARTS, refer to COMPUTERIZED ENGINE CONTROLS.


DESCRIPTION:

To enter diagnostic mode, proceed as follows:

1. Turn the ignition "ON."

2. Press the "OFF" and "TEMP UP" buttons on the ECC panel simultaneously and hold until a segment check is displayed on the IPC and ECC (usually about 3.0 seconds).

NOTE: Operating the vehicle in the "Diagnostic Mode" 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 on "Trickle" charge if vehicle is to be operated in "Diagnostic Mode" without engine running for periods, longer than 1/2 hour.

After "Diagnostic Mode" is entered any trouble codes stored in computer memory will be displayed on the season odometer. Codes may be stored for the ECM/PCM, BCM, or SIR systems. Each trouble code consists of the system abbreviation (E, B, or R) E=ECM/PCM B=BCM R=SIR, a three digit code, 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, E014, etc.). The final digit of the code, a C or an H is used to indicate wether the code is current or history.

If no codes are present for a system, a "NO X CODE" message (with X being the system abbreviation - E, B, or R) will be displayed. If the communication line to a component is not operating, a "NO X DATA" message will be displayed, indicating that the BCM could not communicate with that system. At any time during the display of codes, if the "FAN DOWN" button on the ECCP is depressed, the display of the codes will be bypassed. When the "BI-LEV" button is pressed the ECCP will exit "Diagnostic Mode" and go back to normal vehicle operation.




To clear trouble codes proceed as follows:

1. Enter diagnostics.

2. Select code by system type. After all codes have been displayed and you have decided which control system code (ECM/PCM or BCM) by pressing the "FAN UP" after the "EC?" or "BC?" message is displayed. If you only want to clear BCM codes, you must press "FAN DOWN" after the "EC?" message, since it is displayed first. This process will access the specific system in which you wish to clear codes.

3. Select "CLEAR CODES." After accessing the appropriate system, either ECM/PCM or BCM, test mode messages will be displayed and you must respond by repeatedly pressing the "FAN DOWN" until the "CLR E CODE?" or "CLR B CODE?" message is displayed for the system you accessed. Next, press the "FAN UP" which will result in an "E CODE CLR" or "B CODE CLR" message. Now, press "BI-LEVEL" to exit diagnostics and then re-enter diagnostics to verify if the trouble codes were cleared.

Selection of the "CLEAR CODES?" test type will result in either the message "CODES CLEAR" or "CODES/X NOT CLEAR" being displayed, indicating wether the codes were successfully cleared. This message will appear for 3.0 seconds to indicate that all stored trouble codes have been erased from that systems memory. After 3.0 seconds the display will automatically return to the next available test type for the selected system.

NOTE: SIR code 51 cannot be cleared without the use of an ALDL scan tool. Refer to "SIR TROUBLE CODE CHARTS" under COMPUTERIZED ENGINE CONTROLS/DIAGNOSTIC AND TESTING PROCEDURES/TESTING PROCEDURES/DIAGNOSTIC CHARTS.