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8E - 2
ELECTRONIC CONTROL MODULES
CENTRAL TIMER MODULE (Continued)
OPERATION
The central timer module (CTM) monitors many
hard wired switch and sensor inputs as well as those
resources it shares with other modules in the vehicle
through its communication over the programmable
communications interface (PCI) data bus network.
The internal programming and all of these inputs
allow the CTM to determine the tasks it needs to
perform and their priorities, as well as both the stan-
dard and optional features that it should provide.
The CTM then performs those tasks and provides
those features through both PCI data bus communi-
cation with other modules and hard wired outputs
through a number of driver circuits, relays, and
actuators.These outputs allow the CTM the ability to
control numerous accessory systems in the vehicle.
The CTM monitors its own internal circuitry as
well as many of its input and output circuits, and
will store a Diagnostic Trouble Code (DTC) in elec-
tronic memory for any failure it detects. These DTCs
can be retrieved and diagnosed using a DRBIII scan
tool. Refer to the appropriate diagnostic information.
HARD WIRED INPUTS
The hard wired inputs to the CTM include the fol-
lowing:
• Fused B(+)
• Fused ignition switch output (run-acc)
• Fused ignition switch output (run-start)
• Ground
• Key-in ignition switch sense
• Sliding door switch sense
• Passenger door switch sense
• Driver door switch sense
• PCI bus circuit
HARD WIRED OUTPUTS
The hard wired outputs of the CTM include the fol-
lowing:
• Door lock relay output
• Door unlock relay output
• VTSS indicator driver
MESSAGING
The CTM uses the following messages received
from other electronic modules over the PCI data bus:
• Airbag Deploy (ACM)
• Beep request (CMTC)
• Charging System Failure (PCM)
• Chime request (EMIC)
• Engine RPM (PCM)
• OK to Arm VTSS (PCM)
• Security indicator request (SKIM)
• System Voltage (PCM)
• Valid/Invalid Key (SKIM)
• Vehicle Distance (PCM)
• Vehicle Speed (PCM)
DIAGNOSIS AND TESTING - CENTRAL TIMER
MODULE
WARNING: ON VEHICLES EQUIPPED WITH AIR-
BAGS, DISABLE THE AIRBAG SYSTEM BEFORE
ATTEMPTING ANY STEERING WHEEL, STEERING
COLUMN, SEAT BELT TENSIONER, OR INSTRU-
MENT PANEL COMPONENT DIAGNOSIS OR SER-
VICE. DISCONNECT AND ISOLATE THE BATTERY
NEGATIVE (GROUND) CABLE, THEN WAIT TWO
MINUTES FOR THE AIRBAG SYSTEM CAPACITOR
TO DISCHARGE BEFORE PERFORMING FURTHER
DIAGNOSIS OR SERVICE. THIS IS THE ONLY SURE
WAY TO DISABLE THE AIRBAG SYSTEM. FAILURE
TO TAKE THE PROPER PRECAUTIONS COULD
RESULT IN ACCIDENTAL AIRBAG DEPLOYMENT
AND POSSIBLE PERSONAL INJURY.
The hard wired inputs to and outputs from the
central timer module (CTM) may be diagnosed and
tested using conventional diagnostic tools and meth-
ods. Refer to the appropriate wiring information.
However, conventional diagnostic methods may not
prove conclusive in the diagnosis of the CTM. In
order to obtain conclusive testing of the CTM, the
programmable communications interface (PCI) data
bus network and all of the modules that provide
inputs to or receive outputs from the CTM must also
be checked. The most reliable, efficient, and accurate
means to diagnose the CTM, the PCI data bus net-
work, and the modules that provide inputs to, or
receive outputs from, the CTM requires the use of a
DRBIII scan tool. Refer to the appropriate diagnos-
tic information.
REMOVAL
(1) Disconnect and isolate the battery negative
cable.
(2) Slide the driver seat to the full forward posi-
tion.
(3) Disconnect the wire harness connector for the
seat belt latch. (Fig. 1).
(4) Remove the screws that secure the closeout
panel beneathe the driver seat cushion and remove
the panel.
(5) Remove the screws that secure the central
timer module to the bracket.
(6) Disconnect the wire harness connectors from
the central timer module.
(7) Remove the central timer module from the
vehicle.
INSTALLATION
(1) Position the central timer module in the vehicle
VA
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