F 250 2WD Super Duty V8-7.3L DSL Turbo VIN F (1999)
Multifunction Electronic Control Module: Description and Operation
MODULE CONTROLLED FUNCTIONS
NOTE: The Generic Electronic Module (GEM) must be reconfigured upon replacement. Refer to the NGS Tester help screen on the Ford Service
Function (FSF) card to program tire size and axle ratio.
The generic electronic module (GEM/CTM) incorporates the functions of several different modules into one and offers diagnostics to easily locate
and repair concerns affecting the subsystems that it controls.
The GEM/CTM constantly monitors the systems under its control and reports a concern in the form of a Diagnostic Trouble Code (DTC). A DTC
can be retrieved with the New Generation STAR (NGS) Tester through the communication link.
The GEM/CTM has a sleep function to minimize battery consumption. During the sleep mode, the GEM/CTM turns off all outputs and monitors
only the following:
^
Door ajar (driver door, passenger door, and both rear doors)
^
Ignition (KEY-IN, ACC, and RUN)
^
Remote entry (lock, unlock, and panic)
^
Brake/parking brake switch
^
Headlamp dimmer switch
If a change of status occurs at one of these inputs while the GEM/CTM is asleep, the GEM/CTM will "wake up". when the GEM/CTM awakens, it
performs an internal self-test, and begins normal operation. At this point, all GEM/CTM functions will be operational.
During normal operation, the GEM/CTM can detect and record fault codes. An integral part of the normal GEM/CTM operation is continuous
diagnostic capability. Continuous diagnostics detect errors and change the GEM/CTM control strategy. There is no warning lamp for the
GEM/CTM; therefore, a GEM/CTM DTC will direct you to the physical fault. Examples of faults that may be detected during normal operation
include:
^
GEM/CTM continuous self-test (RAM, ROM, EEPROM, A/D checking)
^
Output driver monitoring (opening circuit/short-to-ground or short to battery)
The GEM/CTM can only detect open circuit/short-to-ground faults when the GEM/CTM is not energizing a load, and short-to-battery faults when
the GEM/CTM is attempting to energize a load. The GEM/CTM controls the following functions:
