RAM 1500 Truck 4WD V8-5.9L VIN Z (2002)
The bus messages are transmitted at a rate averaging 10800 bits per second. Since there is only voltage present when the modules transmit and the
message length is only about 500 milliseconds, it is ineffective to try and measure the bus activity with a conventional voltmeter. The preferred method
is to use the DRB III lab scope. The 12v square wave selection on the 20-volt scale provides a good view of the bus activity. Voltage on the bus should
pulse between zero and about seven and a half volts. Refer to the following figure for some typical displays.
The PCI Bus failure modes are broken down into two categories. Complete PCI Bus Communication Failure and individual module no response. Causes
of complete PCI Bus Communication Failure include a short to ground or battery on the PCI circuit. Individual module no response can be caused by an
open circuit at either the Diagnostic Junction Port or the module, or an open battery or ground circuit to the affected module.
Symptoms of a complete PCI Bus Communication Failure would include but are not limited to:
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All gauges on the EMIC stay at zero
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All telltales on EMIC illuminate
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EMIC backlighting at full intensity
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Dashed lines in the overhead console ambient temperature display
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No response received from any module on the PCI bus (except the PCM)
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No start (if equipped with Sentry Key Immobilizer)
Symptoms of Individual module failure could include any one or more of the above. The difference would be that at least one or more modules would
respond to the DRB III.
Diagnosis starts with symptom identification. If a complete PCI Bus Communication Failure is suspected, begin by identifying which modules the
