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.
Each module on the PCI bus has a small termination load of a parallel resistance and capacitor to make up part of the over all bus termination load. One or two modules on the PCI bus may have a higher load termination to provide stabilizing influence over the variations of vehicle builds. These modules, called dominant modules, may very for car line to car line. The Powertrain Control Module (PCM) is the only dominant node for this vehicle.
Each module provides its own bias and termination 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 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 DRBIII(R) lab scope. The 12 V 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. PCI Bus Communication Failure and individual module no response. Causes of a PCI Bus communication failure include a short to ground or to voltage on any PCI Bus circuit. Individual module no response can be caused by an open circuit at the BCM or at the module, or an open battery or ground circuit to the affected module.
Symptoms of a complete PCI Bus communications failure would include but are not limited to:
- All gauges on the MIC stay at zero
- All Telltales on MIC illuminated
- MIC backlighting at full intensity
- No response received from any module on the PCI Bus through the DRB
- No start (if equipped with sentry key immobilizer system)
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.
Diagnosis starts with symptom identification. If a complete PCI Bus failure is suspected, begin by identifying which modules the vehicle is equipped with and then attempt to get a response from the modules with the DRB. If any modules (except PCM) are responding, the failure is not related to the total bus, but can be caused by one or more modules PCI Bus circuit or power supply and ground circuits. The DRB 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 message used by the DRB 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 with that particular module.
NOTE: Communication over the bus is essential to the proper operation of the vehicles on-board diagnostic systems and the DRB. Problems with the operation of the bus or DRB must be corrected before proceeding with diagnostic testing. If there is a problem, refer to the Communications category.
Bus Failure Message
Odometer Displays "No Bus" - The Mechanical Instrument Cluster (MIC) cannot communicate over the bus and does not know why.
VEHICLE THEFT SECURITY SYSTEM
This passive system is designed to protect against vehicle theft. The vehicle theft security system (VTSS) is part of the body control module (BCM), which monitors vehicle doors and the ignition for unauthorized operation. The alarm activates by sounding the horn, flashing the headlamps, park and tail lamps, and the VTSS indicator lamp. Passive arming occurs upon normal vehicle exit by turning the ignition OFF, opening the driver's door, locking the doors with the power lock, and closing the driver's door or locking the doors with RKE. Manual arming occurs by using the key to lock the doors after closing them. The indicator lamp on the dash will flash for 15 seconds, showing that arming is in progress. If no monitored systems are activated during this period, the system will arm and the indicator will flash at a slow rate. If the indicator lamp remains steadily lit during the arming process, this can indicate a possible loss of communication with the PCM or loss of trunk knock out switch. When something triggers the alarm, the system will signal the headlamps, park lamps, and horn for about 3 minutes.
For complaints about the Theft Alarm going OFF on it's own use the DRBIII(R) and select "Theft Alarm" then "Monitor Display" and read the "Alarm Tripped By" status.
Tamper Alert - The VTSS indicator lamp will flash twice quickly to indicate a tamper condition has occurred.
Manual Override - The system will not arm if the doors are locked using the manual lock control (by hand) or if the locks are actuated by an inside occupant after the door is closed.
To verify the system, proceed as follows:
1. Open the driver's door.
2. Remove the ignition key (but keep it in hand).
3. Lock the doors with the power lock switch or the RKE.
4. Close the driver's door.
NOTE:
- After the doors are closed, locking the doors with RKE will also arm the system.
- If the VTSS indicator lamp flashed, the system is operational and verified. If not, there may be a problem with the system.
Arming/Disarming - Active arming occurs when the remote keyless entry transmitter is used to lock the vehicle doors, whether the doors are open or closed. If one or more doors are open, the arming sequence is completed only after all doors are closed.
Passive disarming occurs upon normal vehicle entry (unlocking either front door with the key). This disarming also will halt the alarm once it has been activated.
Active disarming occurs when the remote keyless entry transmitter is used to unlock the vehicle doors. This disarming also will halt the alarm once it has been activated.
System Self-Tests - NOTE: System self-tests can be entered only with the DRBIII(R).
NOTE: A Powertrain Control Module from a vehicle equipped with a vehicle theft security system cannot be used in a vehicle that is not equipped with a vehicle theft security system. If the VTSS indicator lamp comes ON after ignition ON and stays ON, the PCI bus communication with the Power- train Control Module possibly has been lost.
WIPER SYSTEM
The wiper system provides the driver with the normal wiper (low and high speeds), intermittent wipe, wipe after wash, headlamp washers and pulse wipe functions. The driver selects the wiper function via the resistive multiplexed stalk switch mounted on the steering column. The BCM uses input signal from the wiper stalk switch, wiper motor park switch, and the washer switch to control the wipe system. The Body Control Module (BCM) then controls the relays and timing functions to provide the driver selected features.
System Features
Speed Sensitive Intermittent Wipe Mode
There are 6 individual delay times with a minimum delay of 1/2 second to a maximum of 18 seconds. When the vehicle speed is under 10 MPH (6 KMH), the delay time is doubled providing a range of 1 second to 36 seconds.
Pulse Wipe
When the wiper is in the OFF position and the driver presses the wash button for more than 62 milliseconds, but less than 1/2 second, 2 wipe cycle in low speed mode will be provided.
Park after Ignition OFF
Because the wiper relays are powered from the battery the BCM can run the wipers to park after the ignition is turned OFF.
Wipe after Wash
When the driver presses the wash button for over 1/2 second and then releases it, the wiper will continue to run for 2 additional wipe cycles.
The wiper system utilizes the BCM to control the ON/OFF and hi/low relays for low and hi speed wiper functions, intermittent wiper delay as the switch position changes, pulse wipe, wipe after wash mode, and wiper motor park functions. The BCM uses the vehicle speed input to double the usual delay time below 10 MPH (6 KMH).
USING THE DRB
Refer to the DRB user guide for instructions and assistance with reading trouble codes, erasing trouble codes, and other DRB functions.
DRBIII(R) ERROR MESSAGES
Under normal operation, the DRB will display one of only two error messages: user-requested WARM Boot or User-Requested COLD Boot. If the DRB should display any other error message, record the entire display and call the MDS Hotline, or call for information and assistance at 1-800-8737. This is a sample of such an error message display:
ver:2.14
date: 26 Jul 93
file: key_iff. cc
date: Jul26 1993
line: 548
err: Oxi
User-Requested COLD boot
Press MORE to switch between this display and the application screen. Press F4 when done noting information.
DRBIII(R) Does Not Power Up (Blank Screen)
If the LED's do not light or no sound is emitted at start up, check for loose cable connections or a bad cable. Check the vehicle battery voltage (data link connector cavity 16). A minimum of 11 volts is required to adequately power the DRB. Check for proper grounds at DLC cavities 4 and 5.
If all connections are proper between the DRB and the vehicle or other devices, and the vehicle battery is fully charged, an inoperative DRB may be the result of a faulty cable or vehicle wiring.
DRB Scan Tool:
Display Is Not Visible
Low temperatures will affect the visibility of the display. Adjust the contrast to compensate for this condition.