Specifications

47
Testing Testing Bus Systems
P Bus (Peripheral Bus)
The P Bus (peripheral bus) is found exclusively on vehicles that have a GM III/ZKE III body
module. The P Bus modules are connected to the GM III (General Module) via the P Bus.
NOTE:
i Snap-on
®
scan tools currently do not communicate with the P Bus because it has no GM III (body
control) interface. The P Bus is the only bus that communicates with the GM III module.
The P Bus is only used for body electronics that uses a single copper wire for serial
communications. The P Bus is found on the vehicles in Table 4-20.
Figure 4-4 Sample P Bus connections
The P Bus has the following characteristics:
• The P Bus is similar in communication and speed to the I and K buses.
• Not designed for rapid data communications, instead designed for short control commands
which allows P Bus modules to react more quickly (e.g., door lock or window).
• The GM module sends the Sleep Command to all the P Bus modules 16 minutes after the
ignition is turned off and no messages are being sent.
• The “Walk-up call,” done either by the GM or the driver/passenger door modules, pulls the
P Bus voltage low.
• With every ignition cycle, the GM module polls the P Bus every 5 seconds to see if all the
installed modules respond. The P Bus modules must respond in 5 seconds. If after 3 polling
attempts the poll is unanswered, the GM module sets a fault code.
• The GM module communicates coding data to the modules on the P Bus.
• The GM module provides the 12V P Bus operating voltage.
P Bus Operational Check
Use the following procedure to check the operation of a P Bus.
Table 4-20 BMW models that use the P Bus
Series Models Year
E38 740i/iL, 750iL 1994–2001
E39 525i, 528i, 530i, 540i, M5 1997–2003
E53 X5 3.0/4.4L 1999–2003
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