Diagnostic Modes

Fig. 7 Typical digital electronic fuel injection diagnostic panel:

The ``Service Now'' and ``Service Soon'' lights are used to indicate a malfunction has been detected in the system.
The dash-mounted light(s) is used to indicate system malfunctions or abnormalities. These malfunctions may be related to the various operating sensors or to the ECM. The light(s) goes out automatically if the fault clears (intermittent). However, the ECM stores the trouble code associated with the detected failure until the diagnostic system is ``Cleared'' or until 50 ignition switch on-off cycles have occurred without the fault reappearing.
Proper operation of the light(s) is as follows:
a. The light(s) is normally off.
b. A bulb check is performed when the ignition is in the ON and CRANK positions. When the engine starts, the bulb(s) go out.
c. Either the ``Service Now'' or ``Service Soon'' light will illuminate and remain lit depending on the malfunction detected.
d. If a malfunction is intermittent, the light will go out when the malfunction is not present. The light will come on or flash on and off each time a malfunction is detected.
e. When ``Service Soon'' and ``Service Now'' malfunctions are detected simultaneously, only the ``Service Now'' light will illuminate.
f. Both lights remain lit when the system is in diagnostic mode.
The dash-mounted digital display panel, normally used for the ECC system, can be temporarily directed to display trouble codes stored in the ECM, Fig. 7.

Entering Diagnostic Mode

1. Turn ignition ON.
2. Depress OFF and WARMER buttons on the ECC panel simultaneously and hold until ``..'' appears, Fig. 7. ``(-)1.8.8'' will then be displayed which indicates the beginning of the diagnostic readout.
3. Trouble codes will be displayed on the digital ECC panel beginning with the lowest numbered code. Note that the fuel data panel does not display when the system is in the diagnostic mode.
Trouble codes stored in the ECM's memory may be cleared (erased) by entering the diagnostic mode and then depressing the OFF and HI buttons simultaneously, Fig. 7. Hold until ``.0.0'' appears. After ``.0.0'' is displayed, ``.7.0'' will appear. With this displayed, turn off ignition for at least 10 seconds before re-entering the diagnostic mode.



Exiting From Diagnostic Mode

To get out of the diagnostic mode, depress any of the ECC ``Function'' keys (except Lo or Outside Temperature) or turn ignition switch OFF for ten seconds. Trouble codes are not erased when this is done.