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 (Driver Alert) 30 seconds before the programmed idle time expires. The lamp will start to flash at a rapid rate 30 seconds before the programmed idle time expires when the shutdown timer is programmed to one minute. The lamp will start to flash 90 seconds before the programmed idle time expires when the programmed idle time is 2 minutes or more. The flashing lamp is to alert the driver the engine is about to shut down. To override 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 30 to 90 seconds while the YELLOW lamp is flashing. A diagnostic EVENT code for Override of the Idle Shutdown Timer will be logged in the ECM.