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. Touch the "OFF" and "TEMP UP" buttons on the ECC panel (non CRT) or the "OFF" and "WARM" buttons (CRT models) simultaneously and hold until all display segments light.

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 whether 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-LEVEL" 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 or BCM) you want to clear, select either BCM or ECM by pressing the "HI" (yes) fan button after the "ECM?" or "BCM?" message is displayed. If you only want to clear BCM codes, you must press "LO" (no) fan button, after the "ECM?" 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 or BCM, test mode messages will be displayed and you must respond by repeatedly pressing the "LO" (no) fan button, until the "CLEAR CODES?" message is displayed for the system you accessed. Next, press the "HI" (yes) fan button, which will result in a "CODES CLEARED" message. Now, press "BI-LEV" (RTN) to exit diagnostics and then re-enter diagnostics to verify if the trouble codes were cleared.