Caravan FWD V6-3.3L VIN R (2001)
Body Control Module: Description and Operation
Part 2 of 5
ORC/SIACM Diagnostic Trouble Codes
Airbag diagnostic trouble codes consist of active and stored codes. If more than one code exists, diagnostic priority should be given to the active
codes. Each diagnostic trouble code is diagnosed by following a specific testing procedure. The diagnostic test procedures contain step-by-step
instructions for determining the cause of the trouble codes. It is not necessary to perform all of the tests in this book to diagnose an individual
code. Always begin by reading the diagnostic trouble codes using the DRB. Always begin diagnostic with the Table of Contents. This will direct
you to the specific test(s) that must be performed. Active diagnostic trouble codes for the airbag system are not permanent and will change the
moment the reason for the code is corrected. In certain test procedures, diagnostic trouble codes are used as a diagnostic tool.
Active Codes
The code becomes active as soon as the malfunction is detected or key-on, whichever occurs first. An active trouble code indicates an on-going
malfunction. This means that the defect is currently there every time the airbag control module checks that circuit or component. It is impossible to
erase an active code. Active codes automatically erase by themselves when the reason for the code has been corrected. With the exception of the
warning lamp trouble codes or malfunctions, when a malfunction is detected, the airbag lamp remains lit for a minimum of 12 seconds or as long
as the malfunction is present.
Stored Codes
Airbag codes are automatically stored in the ORC's memory as soon as the malfunction is detected. The exception is the Loss of Ignition Run Only
code which is an active code only. A stored code indicates there was an active code present at some time. However, the code currently may not be
present as an active code, although another code could be active. When a. trouble code occurs, the airbag warning indicator illuminates for 12
seconds minimum (even if the problem existed for less than 12 seconds). The code is stored, along with the time in minutes it was active, and the
number of times the ignition has been cycled since the problem was last detected. The minimum time shown for any code will be one minute, even
if the code was actually present for less than one minute. Thus, the time shown for a code will be one minute, even if the code was actually
present for less than one minute. Thus, the time shown for a code that was present for two minutes 13 seconds, for example, would be three
minutes. If a malfunction is detected a diagnostic trouble code is stored and will remain stored. When and if the malfunction ceases to exist, an
ignition cycle count will be initiated for that code. If the ignition cycle count reaches 100 without a reoccurrence of the same malfunction, the
diagnostic trouble code is erased and that ignition cycle counter is reset to zero. If the malfunction reoccurs before the count reaches 100, then the
ignition cycle counter will be reset and diagnostic trouble. code will continue to be a stored code. If a malfunction is not active while performing a
diagnostic test procedure, the active code diagnostic test will not locate the source of the problem. In this case, the stored code can indicate an area
to inspect. If no obvious problems are found, erase stored codes, and with the ignition on wiggle the wire harness and connectors, rotate the
steering wheel from stop to stop. Recheck for codes periodically as you work through the system. This procedure may uncover a malfunction that
is difficult to locate.
AUDIO SYSTEM
The following radios are all on the PCI Bus system - RBB, RBK, RAZ, RAD, RBT, and RBY The remaining radio also available, the RAS, is
NOT on the PCI Bus. The PCI Bus inputs into the radio are used for VF dimming, remote steering wheel controls and cabin EQ preference. PCI
Bus outputs from the radio are used for the Name Brand Speaker (NBS) relay activation, as well as cabin EQ preference.
The RBB and RBK radios have the capability of containing multiple vehicle unique equalization curves (cabin EQ preferences) within the radio.
These curves will reside in the radio's flash memory. The radio is capable of storing up to 20 unique equalization curves. The latent curves can be
selected via the Front Control Module transmitting a PCI Bus message to the radio in response to a radio request for equalization message. Upon
receipt of a valid equalization select message response, the radio will switch to output the corresponding equalization curve.
All the radios, except the RAS, are capable of displaying faults and allowing certain actuation tests through the use of the DRBIII(R). When
attempting to perform PCI Bus diagnostics, the first step is to identify the radio in use in the vehicle.
When trouble shooting output shorts or "output" error messages, the following applies:
On radios without an external amplifier, the term output refers to the path between the radio and the speaker. This type of circuit can be monitored
all the way through the speaker connections by the radio assembly. When the radio displays a shorted output DTC with this type of system, the
speaker, radio, or wiring could be at fault. The output DTC could refer to the front or rear output or a left or right output. The reason for the
difference is the pairing of the output sections of the radio. Some are paired left and right, others are paired front and rear.
On radios with an external amplifier, the term "output" refers to the circuit between the radio connector and the amplifier. The radio is capable of
monitoring only this portion and can tell nothing about the circuit between the amplifier and the speakers. Consequently, a shorted output DTC on
this type of system would only refer to this circuit. A faulty speaker could not cause this DTC.
Remote Radio Controls
These radios can be controlled via remote radio switches (optional). These switches are located on the back side of the steering wheel. They
control mode, preset, seek up, seek down, volume up and volume down functions.
These functions are inputs to the Body Control Module and can be read with the DRBIII(R) under "body computer" then sensor displays. The
switches are a multiplexed signal to the BCM. The radio control MUX circuit is a 5 volt line that is pulled to ground through different value
resistors built into the switches. This causes a voltage drop to be seen by the BCM and it sends a specific message to the radio on the PCI Bus
