B3000 SE Cab Plus 4 4WD V6-3.0L OHV (2000)
General Module: Description and Operation
Generic Electronic Module (GEM) / Central Timer Module (CTM)
GEM/CTM System Outline
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The GEM is equipped on vehicles with four-wheel drive or with power windows.
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The CTM is equipped on vehicles with two-wheel drive or without power windows.
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The GEM/CTM control system has two modes of operation:
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Normal mode.
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Diagnostic mode.
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When the GEM/CTM is not energizing a load, the GEM/CTM can only detect open circuit and short to ground faults.
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When energizing a load, the GEM/CTM can only detect short to power faults.
Normal Operating Mode
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The normal operation of the GEM/CTM can detect errors.
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An integral part of the normal GEM/CTM operation is the continuous diagnostic capability. Continuous diagnostics detects errors and changes the
GEM/CTM control strategy.
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There is no warning light for the GEM/CTM; therefore, a DTC concern will direct the technician to the GEM/CTM.
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Examples of faults that may be detected during normal operation include:
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GEM/CTM continuous self-test.
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Output driver monitoring (open circuit/short to GND, short to power).
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Illogical combinations of input signals.
Wiper/Washer Subsystem
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The GEM/CTM controls five modes of operation for the wiper. These modes are active only when the ignition switch is in the RUN or ACC
position.
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The GEM/CTM responds to the windshield wiper control commands by interpreting inputs from the multi-function switch.
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The GEM/CTM relay drivers control the wiper HI/LO relay, wiper PARK/RUN relay and the washer pump relay.
Warning Lights and Audible Warning Devices Subsystem
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The GEM/CTM controls all audible warning devices and warning lights.
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The GEM/CTM performs a prove out on all GEM/CTM-controlled indicator/warning bulbs (except the seat belt and door ajar indicator lights) by
turning on the bulb for two seconds after the ignition is turned to run.
Battery Saver Subsystem
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The battery saver feature removes extended interior lamp power drains to the battery.
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The GEM/CTM will keep power available for all interior lights for 45 minutes after the ignition switch is turned OFF.
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The battery saver is reset by:
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Receiving an illuminated entry request.
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Activating a door ajar warning switch.
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Starting the vehicle.
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Turning the ignition to RUN or ACC.
Interior Lamp Subsystem
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The GEM/CTM illuminates the interior courtesy lamps when any door is set ajar or is opened.
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All interior courtesy lamps are turned off when any of the following occurs:
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All doors are closed and illuminated entry feature is not active.
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The ignition switch is turned to RUN.
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Vehicle speed is over 5 mph (8 kmh mph).
Illuminated Entry Subsystem
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The illuminated entry feature (GEM only) activates the interior lamps.
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The GEM illuminates the interior lamps when an unlock signal is received from the RAP module.
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Illuminated entry inputs are:
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RAP illuminated entry request (grounded pulse of varying length).
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Ignition in RUN (battery voltage on both the RUN and RUN/ACC inputs).
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Illuminated entry output is:
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Interior lamp relay coil output.
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Grounded when activated.
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Open circuit when deactivated.
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The RAP module sends a signal to the GEM to turn the illuminated entry on or off.
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Illuminated entry will be canceled if:
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25 seconds have elapsed since the illuminated entry feature was activated and the courtesy lamp feature is not activated.
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If the GEM receives a request from the RAP and the courtesy lamp feature is not activated.
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If the ignition is in the RUN or START position and the courtesy lamp feature is not activated.
Illuminated entry inputs are:
