Malfunction Indicator (Check Engine) Lamp

DESCRIPTION

Fig. 28 Check Engine Lamp Location - Typical:

The malfunction indicator lamp illuminates each time the ignition key is turned on. It will stay on for approximately three seconds as a bulb test. The lamp is displayed on the instrument panel as the CHECK ENGINE lamp.

OPERATION
If the Jeep/Truck Engine Controller (JTEC) receives an incorrect signal, or no signal from certain sensors or emission related systems, the lamp is turned on. This is a warning that the JTEC has recorded a system or sensor malfunction. In some cases, when a problem is declared, the JTEC will go into a limp-in mode. This is an attempt to keep the system operating. It signals an immediate need for service.

The lamp can also be used to display a Diagnostic Trouble Code (DTC). Cycle the ignition switch On-Off-On-Off-On within three seconds and any codes stored in the JTEC memory will be displayed. This is done in a series of flashes representing digits. The lamp is also used to detect certain engine misfires.