GASKET 3B6881 - Caterpillar

"DIAGNOSTIC" lamp is used to indicate the existence of a fault by flashing codes. The "DIAGNOSTIC" lamp that is on the dashboard is usually "YELLOW".When the ignition switch is first turned on, the "DIAGNOSTIC" lamp will go through the following procedure:
The "DIAGNOSTIC" lamp will illuminate for five seconds.
The "DIAGNOSTIC" lamp will turn off.Whenever the Engine Control Module (ECM) detects an active fault or condition the lamp will flash at five second intervals. If the lamp turns on and if the lamp stays on after initial start-up, the ECM has detected a system problem.The "DIAGNOSTIC" lamp is also used for the Idle Shutdown Timer. The lamp will start to flash at a rapid rate 90 seconds before the programmed idle time expires. The engine will shut down after the 90 second interval. To disable the Idle Shutdown Timer, the "ALLOW IDLE SHUTDOWN OVERRIDE" must be programmed to "YES". The clutch pedal or the service brake pedal must be depressed during the final 90 seconds while the "YELLOW" lamp is flashing. A diagnostic "EVENT" code or Override of the Idle Shutdown Timer will be logged in the ECM.