Electronic Control Modules: Overview Chrysler Pacifica CS

DESCRIPTION

The Body Control Module (BCM) is located on the bulkhead left side, underneath the instrument panel. (Scheme 1) The BCM utilizes integrated circuitry and information carried on the Programmable Communications Interface (PCI) data bus network along with many hard wired inputs to monitor many sensor and switch inputs throughout the vehicle. In response to those inputs, the internal circuitry and programming of the BCM allow it to control and integrate many electronic functions and features of the vehicle through both hard wired outputs and the transmission of electronic message outputs to other electronic modules in the vehicle over the PCI data bus.

Scheme 1

OPERATION

The Body Control Module (BCM) is operational when supplied with 12v battery power. The BCM controls various vehicle functions. It also supplies information to the instrument cluster to provide visual and audible information to the vehicle occupants. To provide and receive information, the module interfaces with the vehicle's Programmable Communication Interface (PCI) data bus network. This network consists of the

1. Integrated Power Module (IPM) - which incorporates the Power Distribution Center (PDC) and the Front Control Module (FCM) into one assembly.
2. Next Generation Controller (NGC) - which incorporates the Powertrain Control Module (PCM) and the Transmission Control Module (TCM) into one module.
3. Instrument Cluster (IC)
4. Electronic Vehicle Information Center (EVIC)
5. Occupant Restraint Controller (ORC)
6. Compass/Mini-Trip Computer (CMTC)
7. Overhead Console
8. Controller Antilock Brake (CAB)
9. Automatic Temperature Control Module (ATC)
10. Power Liftgate Module (PLGM)
11. Audio system
12. Memory/Heated Seat Adjustable Pedal Module
13. Sentry Key Remote Entry Module (SKREEM) - which performs the functions of the previous two modules - Remote Keyless Entry (RKE) and Sentry Key Immobilizer Module (SKIM).
14. Driver Door Module (DDM) and the Passenger Door Module (PDM)

The BCM provides

1. A battery protection feature. - The BCM will send a message to the IPM to turn off all exterior lamps after 3 minutes and all interior lamps after 15 minutes after the ignition is turned off, if they are not turned off by the driver.
2. Compass/Minitrip support.
3. Interior lighting (courtesy/reading lamps).
4. Diagnostic reporting.
5. Electronic liftgate release (with power door locks).
6. Exterior lighting.
7. Headlamp time delay (with/without auto headlamps).
8. Automatic headlamps (with electrochromatic mirror).
9. Illuminated entry.
10. A fade to off feature. - This feature dims the interior lighting (courtesy lamps) gradually if the BCM does not receive any new input that would cause the interior lamps to remain on.
11. Pulse Width Modulated (PWM) instrument panel dimming.
12. Power liftgate switch input. - The BCM has 1 Liftgate switch input located in the overhead console.
13. All stalk switch inputs including wipers and light switches.
14. Seat belt position input, indicating a buckled or unbuckled seat belt.
15. Turn signal operation.
16. Fuel Level inputs.
17. Monitors rear-door ajar switches, liftgate ajar switches, multi-function switches, multi-function headlight switch, ignition switch, PCI Bus, and diagnostic tool. Based on input from these components, the BCM will send requests over the PCI Bus to have the Instrument Cluster perform various chime operations.

The BCM has internal diagnostic capabilities that assist in diagnosing the vehicle's body system. When an "Open" or a "Short" circuit exists, the DRBIII(R) scan tool can read the stored BCM Diagnostic Trouble Codes (DTC's). The DTC's are very descriptive in identifying the appropriate feature that has faulted.

Refer to BODY DIAGNOSTIC PROCEDURES for Diagnosis and Testing.

Scheme 2

1. Disconnect and isolate the battery negative cable.
2. Remove the lower instrument panel silencer.
3. Remove the knee blocker airbag «(Refer to ELECTRICAL/RESTRAINTS/KNEE BLOCKER AIRBAG - REMOVAL)»(ref-245421-S08642355362006110200000).
4. Unclip the 72-way bulkhead connector from the Body Control Module (BCM) mounting assembly.
5. Move bulkhead wiring aside.
6. Disconnect the five wire connectors from the BCM.
7. Remove the four screws holding the BCM to the bulkhead. (Scheme 2) 1 - PARKING BRAKE ASSEMBLY 2 - BCM MOUNTING SCREWS 3 - LOWER STEERING COLUMN 4 - BODY CONTROL MODULE
8. Remove the BCM from the mounting bracket.

The Programmable Communication Interface (PCI) data bus is a single wire multiplexed network capable of supporting binary encoded messages shared between multiple modules. The PCI Bus circuit is identified as D25 and is white with a violet tracer. Additional tracer colors may be added to the violet in order to distinguish between different module connections. The modules are wired in parallel. Connections are made in the harness using splices.

The modules used include

1. Body Control Module
2. Integrated Power Module (IPM)
3. Next Generation Controller (NGC)
4. Instrument Cluster (IC)
5. Electronic Vehicle Information Center (EVIC)
6. Occupant Restraint Controller (ORC)
7. Compass/Mini-Trip (CMTC)
8. Overhead Console
9. Controller Antilock Brake (CAB)
10. Automatic Temperature Control Module (ATC)
11. Power Liftgate Module (PLGM)
12. Radio
13. CD Changer
14. Memory/Heated Seat Adjustable Pedal Module
15. Sentry Key Remote Entry Module (SKREEM)
16. Driver Door Module (DDM)
17. Passenger Door Module (PDM)

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 PCI 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 the DRBIII(R) scan tool. The 12v 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.

The PCI Bus failure modes are broken down into two categories. Complete PCI Bus Communication Failure and individual module no response. Causes of complete PCI Bus Communication Failure include a short to ground or battery on the PCI circuit. Individual module no response can be caused by an open circuit at the module, or an open battery or ground circuit to the affected module.

Symptoms of a complete PCI Bus Communication Failure would include but are not limited to

1. All gauges on the cluster stay at zero
2. All telltales on cluster illuminate
3. cluster backlighting at full intensity
4. No response received from any module on the PCI Bus (except the NGC)
5. No start (if equipped with Sentry Key Immobilizer)

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 DRBIII(R).

Diagnosis starts with symptom identification. If a complete PCI Bus Communication 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 DRBIII(R). If any modules are responding, the failure is not related to the total bus, but can be caused by one or more modules PCI circuit or power supply and ground circuits. The DRBIII(R) 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 DRBIII(R) 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.

The Antilock Brake Module (ABM) is a microprocessor-based device which monitors the antilock brake system (ABS) during normal braking and controls it when the vehicle is in an ABS stop or when in a traction control situation. The ABM utilizes a 47-way electrical connector on the vehicle wiring harness. The power source for the ABM is through the ignition switch in the RUN or ON position.

The ABM is mounted to the HCU as part of the Integrated Control Unit (ICU). (Scheme 3) The ICU is located in the engine compartment on the inboard side of the left body frame rail. For information on the ICU, (Refer to BRAKES/HYDRAULIC/MECHANICAL/ICU (INTEGRATED CONTROL UNIT) - DESCRIPTION.

Scheme 3

The primary functions of the Antilock Brake Module (ABM) are to

1. Monitor the antilock brake system for proper operation.
2. Detect wheel locking or wheel slipping tendencies by monitoring the speed of all four wheels of the vehicle.
3. Control fluid modulation to the wheel brakes while the system is in ABS or traction control mode.
4. Store diagnostic information.
5. Provide communication to the scan tool while in diagnostic mode.
6. Illuminate the amber ABS warning indicator lamp.
7. (With traction control only) Illuminate the TRAC ON lamp in the message center on the instrument panel when a traction control event occurs.
8. (with traction control only) Illuminate the TRAC OFF lamp when the amber ABS warning indicator lamp illuminates.

The ABM constantly monitors the antilock brake system for proper operation. If the ABM detects a fault, it will turn on the amber ABS warning indicator lamp and disable the antilock braking system. The normal base braking system will remain operational.

Note. If the vehicle is equipped with traction control, the TRAC OFF lamp will illuminate anytime the amber ABS warning indicator lamp illuminates.

The ABM continuously monitors the speed of each wheel through the signals generated by the wheel speed sensors to determine if any wheel is beginning to lock. When a wheel locking tendency is detected, the ABM commands the ABM solenoid coils to actuate. The coils then open and close the valves in the HCU that modulate brake fluid pressure in some or all of the hydraulic circuits. The ABM continues to control pressure in individual hydraulic circuits until a locking tendency is no longer present.

The ABM contains a self-diagnostic program that monitors the antilock brake system for system faults. When a fault is detected, the amber ABS warning indicator lamp is turned on and the fault diagnostic trouble code (DTC) is then stored in a diagnostic program memory. A latched fault will disable certain system functionality for the current ignition cycle. An unlatched fault will disable certain system functionality until the fault condition disappears. These DTC's will remain in the ABM memory even after the ignition has been turned off. The DTC's can be read and cleared from the ABM memory by a technician using the DRBIII(R) scan tool. If not cleared with a scan tool, the fault occurrence and DTC will be automatically cleared from the ABM memory after the identical fault has not been seen during the next 3,500 miles. Drive-off may be required for the amber ABS warning indicator lamp to go out on the next ignition cycle.

The controller antilock brake (CAB) is a microprocessor-based device which monitors the antilock brake system (ABS) during normal braking and controls it when the vehicle is in an ABS stop. The CAB is mounted to the HCU as part of the integrated control unit (ICU). see scheme 11 The CAB uses a 47-way connector on the vehicle wiring harness. The power source for the CAB is through the ignition switch in the RUN or ON position. The CAB is on the PCI bus.

Scheme 4

The primary functions of the controller antilock brake (CAB) are to

1. Monitor the antilock brake system for proper operation.
2. Detect wheel locking or wheel slipping tendencies by monitoring the speed of all four wheels of the vehicle.
3. Control fluid modulation to the wheel brakes while the system is in ABS or traction control mode.
4. Store diagnostic information.
5. Provide communication to the DRBIII(R) scan tool while in diagnostic mode.
6. Illuminate the amber ABS warning indicator lamp.
7. (With traction control only) Illuminate the TRAC ON lamp in the message center on the instrument panel when a traction control event occurs.
8. (with traction control only) Illuminate the TRAC OFF lamp when the amber ABS warning indicator lamp illuminates.

The CAB constantly monitors the antilock brake system for proper operation. If the CAB detects a fault, it will turn on the amber ABS warning indicator lamp and disable the antilock braking system. The normal base braking system will remain operational.

Note. If the vehicle is equipped with traction control, the TRAC OFF lamp will illuminate anytime the amber ABS warning indicator lamp illuminates.

The CAB continuously monitors the speed of each wheel through the signals generated by the wheel speed sensors to determine if any wheel is beginning to lock. When a wheel locking tendency is detected, the CAB commands the CAB solenoid coils to actuate. The coils then open and close the valves in the HCU that modulate brake fluid pressure in some or all of the hydraulic circuits. The CAB continues to control pressure in individual hydraulic circuits until a locking tendency is no longer present.

The CAB contains a self-diagnostic program that monitors the antilock brake system for system faults. When a fault is detected, the amber ABS warning indicator lamp is turned on and the fault diagnostic trouble code (DTC) is then stored in a diagnostic program memory. A latched fault will disable certain system functionality for the current ignition cycle. An unlatched fault will disable certain system functionality until the fault condition disappears. These DTC's will remain in the CAB memory even after the ignition has been turned off. The DTC's can be read and cleared from the CAB memory by a technician using the DRBIII(R) scan tool. If not cleared with a DRBIII(R) scan tool, the fault occurrence and DTC will be automatically cleared from the CAB memory after the identical fault has not been seen during the next 3,500 miles. Drive-off may be required for the amber ABS warning indicator lamp to go out on the next ignition cycle.

A door module is located behind the trim panel of each front door. The module on the driver side is referred to as the Driver Door Module (DDM), while the module on the passenger side is the Passenger Door Module (PDM). Each door module houses both the front power lock and power window switches. In addition to the power window and power lock switches for its own door, the DDM also houses individual switches for each passenger door power window, a power window lockout switch and the power mirror switch.

The DDM and PDM each utilize integrated circuitry and information carried on the Programmable Communications Interface (PCI) data bus network along with many hard wired inputs to monitor many sensor and switch inputs throughout the vehicle. The DDM and PDM control and integrate many functions and features of the vehicle through both hard wired outputs and messages over the PCI data bus. The functions and features of the DDM include the following

1. Auto unlock
2. Automatic (Rolling Door Locks)
3. Central lock from the key cylinder (driver door only)
4. Central unlock from key cylinder and auto unlock on exit (driver door only)
5. Driver front window and driver rear window, including express down for both
6. Driver memory mirror
7. Driver power mirror
8. Driver heated mirror
9. Door key cylinder disarm on central unlock (driver door only)
10. Door lock inhibit
11. Memory system master - Sends a PCI bus message to the radio, MHSAPM, and PDM to tell them to set (store) a memory location or to recall a memory location.
12. Power door lock
13. Switch learning features
14. Window lockout feature for all passenger power windows

The functions and features of the PDM include the following

1. Power door locks
2. Passenger front and rear window including express down for both
3. Passenger memory mirror
4. Passenger power mirror
5. Passenger heated mirror

The door modules are serviced only as complete units. If a door module is damaged or faulty, the entire door module unit must be replaced.

The microprocessor-based DDM and PDM hardware and software monitors integral and hard wired external switch inputs as well as those resources it shares with other electronic modules in the vehicle through its communication over the PCI data bus network. The internal programming and all of these inputs allow the DDM or PDM microprocessor to determine the tasks it needs to perform and their priorities, as well as both the standard and optional features that it should provide.

The Powertrain Control Module (PCM) is a digital computer containing a microprocessor. see scheme 15 The PCM receives input signals from various switches and sensors referred to as Powertrain Control Module Inputs. Based on these inputs, the PCM adjusts various engine and vehicle operations through devices referred to as Powertrain Control Module Outputs.

Scheme 5

Note. PCM Inputs

1. Air Conditioning Pressure Transducer
2. Ambient temperature Sensor
3. ASD Relay
4. Battery Temperature Sensor (NGC)
5. Battery Voltage
6. Brake Switch
7. Camshaft Position Sensor
8. Crankshaft Position Sensor
9. EGR Position Feedback
10. Engine Coolant Temperature Sensor
11. Heated Oxygen Sensors
12. Ignition sense
13. Intake Air Temperature Sensor
14. Knock Sensor
15. NVLD Assembly
16. Manifold Absolute Pressure (MAP) Sensor
17. Park/Neutral
18. PCI Bus
19. Power Steering Pressure Switch
20. EVAP Purge Return
21. SCI Receive
22. Speed Control
23. Throttle Position Sensor
24. Transmission Control Relay (Switched B+)
25. Transmission Pressure Switches
26. Transmission Temperature Sensor
27. Transmission Input Shaft Speed Sensor
28. Transmission Output Shaft Speed Sensor
29. Transaxle Gear Engagement
30. Vehicle Speed

Note. PCM Outputs

1. Air Conditioning Clutch Relay
2. Automatic Shut Down (ASD) and Fuel Pump Relays
3. Data Link Connector (PCI and SCI Transmit)
4. Double Start Override
5. EGR Solenoid
6. Fuel Injectors
7. Generator Field
8. High Speed Fan Relay
9. Idle Air Control Motor
10. Ignition Coils
11. NVLD Assembly
12. Low Speed Fan Relay
13. MTV Actuator
14. EVAP Purge
15. SRV Valve
16. Speed Control Vent Solenoid
17. Speed Control Vacuum Solenoid
18. 5 Volt Output
19. Torque Reduction Request
20. Transmission Control Relay
21. Transmission Solenoids
22. Vehicle Speed

Based on inputs it receives, the powertrain control module (PCM) adjusts fuel injector pulse width, idle speed, ignition timing, and canister purge operation. The PCM regulates the cooling fans, air conditioning and speed control systems. The PCM changes generator charge rate by adjusting the generator field.

The PCM adjusts injector pulse width (air-fuel ratio) based on the following inputs.

1. Battery Voltage
2. Intake Air Temperature Sensor
3. Engine Coolant Temperature
4. Engine Speed (crankshaft position sensor)
5. Exhaust Gas Oxygen Content (heated oxygen sensors)
6. Manifold Absolute Pressure
7. Throttle Position

The PCM adjusts engine idle speed through the idle air control motor based on the following inputs.

1. Brake Switch
2. Engine Coolant Temperature
3. Engine Speed (crankshaft position sensor)
4. Park/Neutral
5. Transaxle Gear Engagement
6. Throttle Position
7. Vehicle Speed

The PCM adjusts ignition timing based on the following inputs.

1. Intake Air Temperature
2. Engine Coolant Temperature
3. Engine Speed (crankshaft position sensor)
4. Knock Sensor
5. Manifold Absolute Pressure
6. Park/Neutral
7. Transaxle Gear Engagement
8. Throttle Position

The automatic shut down (ASD) and fuel pump relays are mounted externally, but turned on and off by the powertrain control module through the same circuit.

The camshaft and crankshaft signals are sent to the powertrain control module. If the PCM does not receive both signals within approximately one second of engine cranking, it deactivates the ASD and fuel pump relays. When these relays are deactivated, power is shut off to the fuel injectors, ignition coils, fuel pump and the heating element in each oxygen sensor.

The PCM engine control strategy prevents reduced idle speeds until after the engine operates for 320 km (200 miles). If the PCM is replaced after 320 km (200 miles) of usage, update the mileage in new PCM. Use the DRBIII(R) scan tool to change the mileage in the PCM. Refer to POWERTRAIN DIAGNOSTIC PROCEDURES and the DRBIII(R) scan tool.

A Memory Heated Seat/Adjustable Pedal Module (MHSAPM) is used on vehicles that are equipped with the heated seat system option. A Memory Seat/Adjustable Pedal Module (MSAPM) is used on vehicles that are not equipped with the heated seat system option. This module contains all the software and control logic for the front memory/heated and power seat systems, as well as the adjustable foot pedal system. The memory heated seat/adjustable pedal module contains a central processing unit and interfaces with the Programmable Communications Interface (PCI) data bus circuit. Refer to the HEATED SEAT SYSTEM for more information on the heated seat system. Refer to the POWER SEAT SYSTEM for more information on the power/memory seat system.

The module is packaged in a black molded plastic case which is mounted under the edge of the driver side front seat cushion. This location makes it somewhat difficult to access because it sits between the power seat track and the seat cushion frame. Refer to the following procedures for detailed removal and installation instructions.

For diagnosis of the MHSAPM or the PCI data bus, a DRB III(R) scan tool and BODY DIAGNOSTIC PROCEDURES article are recommended. The Memory Heated Seat/Adjustable Pedal Module cannot be adjusted or repaired and, if faulty or damaged, it must be replaced.

The Memory Heated Seat/Adjustable Pedal Module controls the heated, power and memory seat systems as well as the adjustable foot pedal system. However different, these systems share some software inside the module. Refer to the following text which explains how the different systems are controlled by the memory heated seat/adjustable pedal module.

FRONT HEATED SEAT SYSTEM OPERATION

When either of the front heated seat switches are depressed a resistor multi-plexed signal is sent to the corresponding door module (Driver or Passenger). The applicable Door Module then sends a message via the Programmable Communications Interface (PCI) data bus network to the Memory Heated Seat Adjustable Pedal Module (MHSAPM), signaling the module to energize the heating element for the selected seat. Light Emitting Diodes (LEDS) in each switch indicate the level of heat in use. The switch LEDs are controlled by the applicable Door Module.

The MHSAPM energizes an integral solid-state relay, which supplies battery current to the seat heating elements. When high-temperature heating is selected, the heaters provide a boosted heat level during the first four minutes of operation after heating is activated. The heat output then drops to the normal selected-temperature level. If high-level heating is selected, the control system will automatically switch to the low level after two hours of continuous operation. Operation on the low setting turns off only when the ignition switch is turned off or the heated seat switch is pressed a second time indicating an off command.

MEMORY SEAT SYSTEM OPERATION

Depressing any of the drivers front door trim panel mounted, memory seat switches sends a hardwired, resistor multi-plexed signal to the drivers door module. The door module then sends a PCI data bus message to the Memory Heated Seat/Adjustable Pedal Module (MHSAPM). The module detects the memory seat switch status via the PCI data bus circuit and energizes the appropriate power seat motors. The programmed software in the MHSAPM allows it to know the location of the seat track by a resistance value generated from the seat track mounted potentiometers. When the correct preset location is achieved the module will de-energize the power seat track motors. The MHSAPM will prevent the seat memory recall function from being initiated if the transmission gear selector lever is not in the Park or Neutral positions, or if the vehicle is moving. These inputs are monitored over the PCI data bus circuit.

ADJUSTABLE FOOT PEDAL SYSTEM OPERATION

Depressing the adjustable foot pedal switch sends a hardwired, resistor multi-plexed signal to the drivers door module. The door module then sends a PCI data bus message to the Memory Heated Seat/Adjustable Pedal Module (MHSAPM). The module detects the adjustable pedal switch status via the PCI data bus circuit and energizes the appropriate foot pedal motor. When the foot pedal switch is released the module will stop the motor.

Depressing the memory switch will signal the module to move the pedal assembly to the preprogrammed position. The programmed software in the MHSAPM allows it to know the location of the foot pedal assembly by a resistance value generated from the pedal assembly mounted potentiometer. When the correct preset location is achieved the module will de-energize the foot pedal motor. The MHSAPM will prevent the adjustable foot pedal function from being initiated if the transmission gear selector lever is not in the Park or Neutral positions, or if the vehicle is moving. These inputs are monitored over the PCI data bus circuit also.

See also:
• BODY DIAGNOSTIC PROCEDURES
• POWERTRAIN DIAGNOSTIC PROCEDURES