Concorde V6-2.7L VIN V (2001)
Body Control Module: Description and Operation
Part 4 of 5
SENTRY KEY IMMOBILIZER SYSTEM (SKIS)
The SKIS is an immobilizer system designed to prevent unauthorized vehicle operation. The system consists of a Sentry Key Immobilizer Module
(SKIM) and ignition key(s) called Sentry Key(s) which are equipped with a transponder chip. The SKIM communicates over the Programmable
Communication Interface multiplex system (PCI) bus network to the Body Control Module (BCM), Powertrain Control Module (PCM), and/or the
DRB scan tool. For programming the Sentry Key Transponder and other technical information refer to Powertrain information.
SPEED PROPORTIONAL STEERING (IF EQUIPPED)
The Speed Proportional Steering automatically adjusts steering effort based on the vehicle speed. The amount of effort required to turn the steering
wheel is determined by a 500-Hz Pulse Width Modulated (PWM) output signal. The desired duty cycle of the PWM is selected from a calibration
table internal to the Body Control Module (BCM).
To obtain the desired solenoid current the duty cycle of the solenoid can be compensated according to a current measuring feedback circuit. The
speed proportional steering system is always active with the ignition ON.
The 500Hz PWM output signal is capable of generating a duty cycle from 0% (full OFF - minimum steering assist) to approximately 50% duty
cycle (full ON - maximum steering assist) in small increments. The duty cycle is determined by vehicle speed and is continuously modified by
solenoid current feedback information. With the engine running and vehicle speed between 0 kmh (0 mph) and approximately 32 kmh (20 mph)
the duty cycle will be about 50%. Between approximately 32 kmh (20 mph) and 100 kmh (60 mph) the duty cycle will gradually decrease to 0%
based upon vehicle speed. Above approximately 100 kmh (60 mph) there is no assist provided by the speed proportional steering system.
Maximum solenoid current will be limited to one amp but the system operates at about 0.5 amp. Speed Proportional Steering Solenoid resistance
is 5.7-6.3 ohms at 20 °C (68 °F).
The Speed Proportional Steering System can detect three failure modes relating to the Speed Proportional Steering PWM driver located in the
BCM. If any DTC is set, the solenoid is shut off, unless the condition goes away before approximately 10 seconds. Once the DTC is set, the
solenoid will remain OFF for the remainder of the ignition cycle.
1. An open or shorted to ground circuit fault is detected by monitoring the feedback circuit. If the BCM detects that the feedback circuit has zero
current when the software indicates the solenoid circuit should have current, the DTC will be set. This test is performed every 250
milliseconds.
2. A short to voltage fault is detected by monitoring the feedback circuit. The DTC will be set when the BCM has sensed that there was current
on the solenoid feedback circuit when the solenoid was turned OFF.
3. An over temperature or thermal shutdown DTC will be set by default if the internal diagnostic pin of the solenoid driver is at a low level, but
the feedback measurement does not show a high PWM output current.
VEHICLE COMMUNICATION
The Chrysler Programmable Communication Interface multiplex system (PCI bus) consists of a single wire. The Body Control Module (BCM)
acts as a splice to connect each module and the Data Link Connector (DLC) together. Each module is wired in parallel to the data bus through its
PCI chip set and uses its local ground as the bus reference. The wiring is a minimum 20 gage. The PCI bus wire insulation color will be violet with
a yellow tracer. An extra tracer color may be added along with the violet to help distinguish between different node connections.
The bus is designed to handle a maximum number of nodes to meet all of the bus load and timing requirements. The bus resistance and
capacitance is designed to provide a maximum level of filtering without distorting the bus symbols. This is why extra capacitance and resistance
should not be added to the PCI Data Bus circuitry.
In order for an electronic control module to communicate on the PCI data bus, the module must have bus interface electronics consisting of a
transmitter/receiver (or transceiver) and Logic control, bus termination for loading and filtering the bus, and wiring which interconnects the
system.
Because of the unique coding scheme used in the PCI bus, each module is required to have logic control. The data moving on the bus is called
symbols. The interface logic performs the following functions: encode and decodes binary data into symbols, synchronizes all bus symbol timing
and edges, controls the sending and receiving of messages, monitors for bus arbitration, monitors for corrupted symbols due to noise and controls
the transceiver.
The bus logic control also provides the transceiver with the information it needs to transmit symbols on the bus. The transceiver controls the wave
shaping of each symbol that it transmits by using internal voltage controlled current drivers. When the bus transceiver is turned ON, the bus driver
ramps up the voltage to the set range and maintains this voltage until the driver is turned OFF, at which time the voltage is ramped back down to
the low voltage, ground. The transceiver is designed to allow for arbitration between modules. If more than one module is trying to access the PCI
bus at one time, the code determines the message that has the higher priority, and is then allowed to access the bus first.
The PCI bus requires a resistance and capacitance termination load to ground to operate. Because each bus transceiver can only source current to
the bus, the resistance load is required to sink this current and pull the bus to ground on the falling edge of the symbols. The bus resistance is
minimum of 315 ohms to a maximum of 2 K ohms. The termination capacitance is required for noise filtering and to help in the symbol wave
shaping. The bus capacitance shall not be greater then 12,000 pf.
