B4000 Regular Cab 4WD V6-4.0L OHV (1997)
General Module: Description and Operation
Central Timer Module
Central Timer Modules (CTM) are equipped only on two-wheel drive vehicles without power windows and/or power locks. All other vehicles have a
generic electronic module (GEM).
NOTE:
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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 grounding the black one-pin diagnostic connector.
The CTM incorporates the function of several different modules into one and offers diagnostics to easily locate and repair concerns affecting the
subsystems that it controls.
The CTM constantly monitors the systems under its control and reports a concern in the form of diagnostic trouble code (DTC). A DTC can be
retrieved by performing a three-step self-test. When the diagnostic mode is activated, the CTM will output trouble codes, if any, to the technician by
flashing the door ajar lamp and simultaneously sounding the chime in a certain order. These codes may then be used to help diagnose potential
intermittent failures.
NOTE:
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The CTM can only detect open circuit/short to ground faults when it is not energizing a load and short to battery faults when the CTM is
attempting to energize a load.
NOTE:
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The CTM has a sleep function to minimize battery consumption. During the sleep mode, the CTM turns off all outputs and monitors only the
following:
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Door Ajar (driver's and passengers door)
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Key is inserted or removed
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The ignition switch is turned from OFF to ON
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The ignition switch is turned from OFF to ACC
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Driver's door handle switch is activated
If a change in status occurs at one of these inputs while the CTM is "asleep", the CTM will "wake up". When the CTM awakens, it performs an
internal self-test and begins normal operation. At this point, the CTM will have all of its functions operational.
The CTM will go into the sleep mode immediately after both of the following conditions have been met:
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Key in OFF or key not in ignition
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After 40 minutes with no change on any wake-up input
The CTM control system has two modes of operation, the normal operation mode and tester dependent diagnostics mode.
Normal operation of the CTM can detect errors. An integral part of the normal CTM operation is the continuous diagnostics capabilities. Continuous
diagnostics detects errors and changes the CTM control strategy. There is no warning light for the CTM; therefore, a DTC will direct you to the CTM.
Examples of faults that may be detected during normal operation include CTM continuous self-test (RAM, ROM, EEPROM, AID checking), illogical
combinations of input signals and output driver monitoring (open circuit/short to ground, short to battery).
NOTE:
^
The CTM can only detect open circuit/short to ground faults when it is not energizing a load and short to battery faults when the CTM is
attempting to energize a load.
