General Module: Description and Operation

Central Timer Modules (CTMs) are equipped on two-wheel drive vehicles without power windows. All other vehicles have a Generic Electronic Module (GEM).

NOTE: CTM diagnostics are not compatible with the New Generation STAR (NGS) Tester; instead, the diagnostics are internal to the module. The diagnostic mode is entered by shorting two pins of the diagnostic connector together.

The GEM inputs and outputs are designed to withstand continuous exposure to a short circuit to ground or battery voltage without being damaged.

GEM Diagnostics
The GEM diagnostics are accessible with the New Generation Star Tester and the Service Bay Diagnostic System (SBDS). The GEM constantly monitors its subsystems for concerns. If a concern is found in one of the subsystems, the GEM will record the concern in the form of a Diagnostic Trouble Code (DTC).

There are three areas of diagnostic information useful when diagnosing the GEM.
^ DTCs A record of past or present system problems.
^ PIDs - The present state of an input or output.
^ Active Commands Gives the ability to turn on GEM outputs without activating the inputs normally associated with the function.

Ignition Switch Positions
The position of the ignition switch is very important to proper GEM operation. Often times, erratic or unexpected operation can be traced to problems on these GEM inputs. The following is a brief description of five ignition switch positions.

When the ignition switch is in the RUN position, battery voltage should be present at the GEM/CTM RUN and RUN/ACC input terminals When the ignition switch is in the ACC position, battery voltage should be present at the GEM/CTM RUN/ACC input terminal only.

When the ignition switch is in the START position, battery voltage should be present at the GEM/CTM start/clutch depressed input.

The GEM module does not have an OFF or LOCK Switch State input. The GEM will assume the OFF or LOCK position when there are no RUN, ACC, or START signals present.

GEM Features and Functions

GEM Feature Matrix:

The GEM controls the following features:
^ Wipers/washers.
^ Warning chimes.
^ Battery saver.
^ Illuminated entry and courtesy lamps.
^ Driver power window
^ Accessory delay.
^ 4-wheel drive

Wiper/Washer Control and Interval Timer
There are four modes of operation for the wipers: interval (standard CTM and speed-dependent GEM), LOW, HI, and wash. These modes are only active with the ignition switch in the RUN or ACC position. Speed dependent wipers compensate for the extra moisture that accumulates on the windshield at higher speeds. At higher speeds, the speed dependent feature shortens the delay between wipers when using the variable interval wiper feature. Delays will automatically adjust at speeds between 16 and 105 km/h (10 and 65 mph).

Chime Warning
There are four warning chimes and lamps that are controlled by the GEM and CTM: headlamps operating without the ignition on (chime only), door ajar (chime and lamp), key in the ignition (chime only), and driver seat belt warning (chime and lamp).

Battery Saver
The battery saver feature removes extended interior lamp power drains from the battery. The GEM and CTM will keep power available for all interior lights and hood lamp circuits for 40 minutes after the ignition switch is turned OFF. The battery saver timer is reset by lifting a door handle (GEM only), activating a door ajar switch, unlocking door with the keyless entry remote transmitter, or changing the ignition to RUN or ACC position. If asleep, the GEM and CTM will wake up when one of the following occurs:
^ Any door becomes ajar or is closed.
^ The key is inserted or removed.
^ The ignition switch is turned to ACC or RUN.
^ The doors are unlocked with the keyless entry remote transmitter.

Courtesy Lamps/Illuminated Entry
The GEM/CTM illuminates the interior courtesy lamps when any door is ajar. The GEM also receives a signal from the Remote Anti-theft Personality (RAP) module for keyless entry illumination. All interior courtesy lamps are turned off when any of the following occur:
^ Twenty-five seconds have elapsed since the illuminated entry feature was activated.
^ The ignition switch is turned to RUN.
^ Vehicle speed is over 25 km/h (15 mph) (a new ajar signal will turn on courtesy lamps only if the vehicle speed is less than 16 km/h (10 mph) - GEM only).

Delayed Accessory (GEM only)
The delayed accessory feature provides power to the power windows for ten minutes after the ignition switch is moved from the RUN to the OFF position. If during this ten-minute period either door is opened, the delayed accessory relay will be de-energized.

One-Touch Down Window (GEM only)
The power switch for the driver window control has two detents for the down window control. With the ignition switch in RUN or ACC, pressing the first detent (normal mode) allows manual down window control; pressing the switch farther to the second detent (auto) will cause the driver window to automatically move to the full down position. Pressing either the up or down window switch will cancel an auto mode operation in progress.

Transfer Case (4-Wheel Drive - GEM Only)
Two types of 4-wheel drive systems are offered: the Mechanical Shift-On-the-Fly (MSOF) and the Electronic Shift-On-the-Fly (ESOF).

RAP-Controlled Functions
The RAP module controls the door locks through three external relays located under the instrument panel relay cover:
^ Driver unlock relay.
^ All unlock relay.
^ All lock relay.

The RAP module receives input from the following components for electronic door lock system operation:
^ Keyless entry remote transmitters.
^ Door ajar output from the GEM.
^ Door unlock switches (LH/RH).
^ Brake Pedal Position (BPP) switch.
^ Digital Transmission Range (DTR) sensor.