•
Satellite Radio Receiver (if equipped)
•
Window Regulator Modules (PT27) - Driver and
passenger
Each module provides its own bias and termina-
tion in order to transmit and receive messages. The
bus voltage is at zero volts when no modules are
transmitting and is pulled up to about seven and a
half volts when modules are transmitting.
The bus messages are transmitted at a rate
averaging 10,800 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 DRBIII
t 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 figure for some typical displays.
The PCI Bus failure modes are broken down into
two categories. PCI Bus Communication Failure
and individual module no response. Causes of a 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 the module, or an open battery or ground
circuit to the affected module.
Symptoms of a PCI Bus Communication Failure
would include but are not limited to:
•
All gauges on the EMIC stay at zero
•
All telltales on EMIC illuminate
•
EMIC backlighting at full intensity
•
No response received from any module on the PCI
bus (except PCM/ECM)
•
No start (if equipped with Sentry Key Immobi-
lizer)
Symptoms of individual module failure could in-
clude any one or more of the above. The difference
would be that at least one or more modules would
respond to the DRBIII
t.
Diagnosis starts with symptom identification. If a
PCI Bus Communication Failure is suspected, be-
gin by identifying which modules the vehicle is
equipped with and then attempt to get a response
from the modules with the DRBIII
t. If any modules
are responding, the failure is not related to the total
bus, but can be caused by one or more modules PCI
circuit or power supply and ground circuits. The
DRBIII
t may display “BUS +/- SIGNAL OPEN” or
“NO RESPONSE” to indicate a communication
problem. These same messages will be displayed if
the vehicle is not equipped with that particular
module. The CCD error message is a default mes-
sage used by the DRBIII
t and in no way indicates
whether or not the PCI Bus is operational. The
message is only an indication that a module is
either not responding or the vehicle is not equipped.
15
GENERAL INFORMATION