Part 2 of 2
VEHICLE COMMUNICATIONThe body system consists of a combination of modules that communicate over the CCD (Chrysler Collision Detection multiplex system) bus. Through the CCD bus, information about the operation of vehicle components and circuits is relayed to the appropriate module(s). Each module receives the same information about a component or circuit as the other modules do. This significantly reduces the complexity of the wiring in the vehicle and the size of the wiring harnesses.
The Chrysler Collision Detection multiplex system (CCD bus) consists of a twisted pair of wires. These wires run from one module to another. They receive and deliver coded information between the modules. The information is coded to identify the message as well as the importance of the message. When there are multiple messages trying to access the CCD bus at one time, the code determines the message that has higher priority, which is then allowed to access the bus first.
The two wires of the twisted pair that make up to CCD multiplex systems are called "bus+" (bus plus) and "bus-" (bus minus) respectively. Each wire has a measurable voltage level of roughly 2.5 volts. In order to maintain the 2.5 volts on each line and provide a means of transportation for the coded messages, there is "voltage divider network." This network consists of some modules with bias and some with termination. Bias is the part of the voltage divider network that places both bus+ and bus at 2.5 volts. Termination in the circuitry is required to complete the voltage divider network and also to provide some electromagnetic protection for the bus.
NOTE: COMMUNICATION OVER THE BUS IS ESSENTIAL TO THE PROPER OPERATION OF THE VEHICLE'S ON-BOARD DIAGNOSTIC SYSTEMS AND THE DRBIII(R). PROBLEMS WITH THE OPERATION OF THE BUS OR DRBIII(R) MUST BE CORRECTED BEFORE PROCEEDING WITH DIAGNOSTIC TESTING. IF THERE IS A PROBLEM, REFER TO THE VEHICLE COMMUNICATION FOR DIAGNOSTIC AND REPAIR PROCEDURES.
Any of the following bus failure messages may be displayed:
Short to Battery - Either or both of the bus wires are shorted to the battery potential.
Short to 5 Volts - Either or both of the bus wires are shorted to a 5 volt potential.
Short to Ground - Either or both of the bus wires are shorted to ground or a specific ground may be open.
Bus (+) & (-) Shorted Together - The two bus wires are shorted together.
No Termination - The bus system has lost connection with all of its terminators.
Bus Bias Level Too Low - Either or both of the bus wire potentials are significantly below their normal 2.5 volts.
Bus Bias Level Too High - Either or both of the bus wire potentials are significantly above their normal 2.5 volts.
No Bus Bias - The bus system has lost connection with all modules that provide bias.
Bus (+) Open - The bus (+) wire has lost connection with termination and/or bias.
Bus (-) Open - The bus (-) wire has lost connection with termination and/or bias.
Not Receiving Bus Messages Correctly - The DRB 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) module is a logic-controlled device (part of the body control module), that monitors vehicle doors, trunk key cylinder and ignition action for unauthorized operation. The alarm activates by sounding the horn, flashing the headlamps, courtesy and VTSS lamps and providing an engine "no run" feature which is accomplished by the Sentry Key Immobilizer System.
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. Manual arming occurs by using the key to lock the doors after closing them.
The indicator lamp in the cluster will flash fast for 15 seconds, showing that arming is in progress. If no monitored systems are activated during this period, the system will arm. If the trunk key cylinder switch is not seen by the system, the indicator lamp will remain steadily lit during the arming process, although the system will still arm. The indicator lamp blinks at a slow rate when the system is armed.
Once the VTSS is armed the universal garage door opener (if equipped), vanity lights and the decklid release switch in the center console will be disabled, The decklid release will still operate from the RKE or using the key.
When something triggers the alarm, the system will signal for about 18 minutes. For the first three minutes the horn will sound, then the headlamps and courtesy lamps will continue to flash for another 15 minutes.
Tamper Alert - If the horn sounds three times when either front door is unlocked, it means the alarm was activated. Check the vehicle for tampering. The VTSS indicator lamp will also 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.
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.
4. Close the driver's door.
NOTE: IF THE VTSS INDICATOR LAMP FLASHED, THE SYSTEM IS OPERATIONAL AND VERIFIED. IF NOT, THERE MAY BE A PROBLEM WITH THE SYSTEM.
System initialization is accomplished by communication between the powertrain control module and the body control module using the DRBIII(R).
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 starts 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.
System Self-Tests - NOTE: System self-tests can be entered only with the DRBIII(R).
Upon entering diagnostics, the headlamps, courtesy lamps and VTSS lamp will begin flashing to verify their operation. In addition, the horn will sound twice. Removing the key from the ignition switch will stop the lamps from flashing while keeping the system in diagnostics.
While in diagnostics mode, a horn pulse should occur at each of the following events, which indicate proper operation.
1. Beginning with all doors closed, open, then close each door. The horn will sound when the door ajar switch closed, and then again when the switch opens. There must be a one second delay between closing and opening the switch.
2. Rotate the key in each door lock cylinder to unlock position. The horn will sound as the switch closes, and again when it opens. There must be a one second delay between changing switch states, or the horn will not sound.
3. Cycle the key to the ignition RUN position. A single horn pulse will indicate proper operation of the ignition input. This also will take the module out of the diagnostics mode.
For any of these tests, if the switch does not remain open or closed for at least one second, the horn will only sound once.
The lack of a horn pulse during any operation indicates either:
- A switch failure
- The lack of that input to the body control module
- A failure internal to the module
- A faulty horn system
Check for continuity at the switch. If this is good, check for an open or shorted wire between the switch and the BCM. Also, check if the Powertrain Control Module (PCM) has been replaced recently.
NOTE: A PCM 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 stay ON, the CCD bus communication with the PCM possibly has been lost.
WIPER SYSTEM
The wiper system provides the driver with normal wipe (low and high speeds), intermittent wipe, wipe after wash and mist wipe functions. The driver selects the wiper function via a resistive multiplexed stalk switch mounted on the steering column.
Other wiper system features:
Speed Sensitive Intermittent Wipe Mode - There are six 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, the delay time is doubled providing a range from one second to 36 seconds.
Mist Wipe - When the wiper is off and the driver presses the mist control for more than 125 millisecond, one wipe cycle in low speed mode will be provided. The wipe will continue in low speed as long as the switch is held in that position.
Wiper After Wash Mode - When the driver presses the wash button for over 3/8 second and then releases it, the wiper will continue to run for two additional wipe cycles.
AIRBAG 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 code(s).
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 DRBIII(R). Then perform the specific test(s). If more than one code exists, diagnostic priority should be given to the active code(s).
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
An active trouble code indicates an ongoing malfunction. This means that the defect is currently there every time the airbag control module checks that circuit/function. 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 ACM's memory when the ignition is turned off with the exception of 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 active code could be.
When a trouble code occurs, the AIRBAG warning lamp 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 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 as long as the malfunction exists. 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 that same malfunction, that 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 the 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, rotating 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.
Airbag Trouble Codes
The airbag control module may report any of the following diagnostic trouble codes.
For these codes, replace the Airbag Control Module (ACM) even if set intermittently:
- AECM Accelerometer
- AECM Internal Diagnostic 1
- AECM Internal Diagnostic 2
- AECM Output Driver
- AECM Stored Energy
For these codes, refer to the appropriate diagnostic procedure:
- AECM & Cluster CCD Message Mismatch
- Driver Squib Circuit Open
- Driver Squib Circuit Shorted
- Driver Squib Term Shorted to Battery
- Driver Squib Term Shorted to Ground
- Loss of Ignition Run Only
- Loss of Ignition Run/Start
- No CCD Communication
- No Cluster CCD Bus Message
- Passenger Squib Circuit Open
- Passenger Squib Circuit Shorted
- Pass Squib Term Shorted to Battery
- Pass Squib Term Short to Ground
- Warning Lamp Circuit Open
- Warning Lamp Circuit Shorted
- Output Driver Not Tested
BODY TROUBLE 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 trouble codes.
Always begin by reading the diagnostic trouble codes using the DRBIII(R). The following is a list of the possible diagnostic trouble codes that may be displayed from the BCM:
- Battery Power to Module Disconnected
- Driver Door Disarm Switch Input
- EATX PRNDL Message Test Failed
- EEPROM Checksum Failure
- Evaporator Sensor Failure
- Fuel Level Sending Circuit Error
- HVAC Control Input Shorted to Battery
- HVAC Control Input Shorted to Ground
- HVAC Mode Door Feedback Failure
- HVAC Mode Door Stall
- Internal Module Tests Failed
- Panel Lamp PWM Output Failure
- Passenger Door Disarm Switch Input
- Rear Defogger Button Stuck
- Wiper Park Switch Failure