Mode Description

NORMAL OR OPEN MODE

Not all engines and ECM families will transmit information on the serial data line while in this mode.
On engines that can be monitored in the open mode, it allows certain parameters to be obtained without changing the engine operating characteristics. The parameters capable of being read vary from engine family to engine family. Most ``SCAN'' tools are programmed so that the system will go directly into the special mode and the ``open'' mode must be selected when it is available.

10K MODE, SPECIAL MODE OR ALDL MODE

In this mode, all information incorporated into a specific engine and ECM is obtainable, but the system operating characteristics are modified. Closed loop timers are bypassed, EST (spark) is advanced, IAC controls engine idle to 950-1050 RPM, canister purge solenoid will be disabled on some engines and park/neutral restrict functions will be disabled.

FACTORY TEST MODE, BACK-UP OR 3.9K MODE

When in this mode, the ECM is operating on the fuel back-up logic and calibrated by the CALPAK. The CALPAK is used to control fuel delivery if the ECM fails. This mode verifies that the back-up feature is working. The parameters available to be read on a ``SCAN'' tool in this mode will be of very little use for service.