Description of On-Board Diagnostics

This system is equipped with self-diagnosis capabilities. To ensure proper diagnosis, the following testing sequence should be performed as indicated.
A system Diagnostic Circuit Check should be made first to ensure the system self-diagnosis is operating properly, to determine if the trouble codes will display and to guide diagnosis to the proper problem area.
On Pickup & Trooper II, after performing the Diagnostic Circuit Check and the ``Check Engine'' lamp did not light, refer to Drivers Complaint for an emission non-compliance problem or an engine performance problem.
On all models, perform the System Performance Check next to check the operation of the mixture control solenoid and the Closed Loop Emission Control System.