Usage:
The "check engine" light, on the truck dashboard, can be used as a diagnostic lamp to communicate status or operation problems of the electronic control system.
Trucks With Cruise
The dash mounted cruise switches are used to interrogate the ECM for system status. With the cruise switch in the "off" position, hold the set/resume switch in the resume position until "check engine" light begins to flash. The sequence of flashes represents the system diagnostic message. The first sequence of flashes adds up to the first digit of the fault code. After a one second pause, a second sequence of flashes will occur which represents the second digit of the fault code. Any additional fault codes will follow, after a pause, and will be displayed in the same manner.
Trucks Without Cruise
Use the Engine Diagnostic Light Switch, if equipped, to check the fault codes. Otherwise a push button momentary switch should be connected from position H of connector P7 to ground. Depress this switch until the "check engine" light begins to flash. The sequence of flashes represents the system diagnostic message. The first sequence of flashes adds up to the first digit of the fault code. After a one second pause, a second sequence of flashes will occur which represents the second digit of the fault code. Any additional fault codes will follow, after a pause, and will be displayed in the same manner.