Powertrain Control
Computer Inputs And Outputs:
SYSTEM DESCRIPTION:
The Powertrain used in this vehicle consists of a 4.6L dual overhead cam engine mated to a 4T80-E electronically controlled transaxle. It has controls to reduce emissions while maintaining excellant driveablity and fuel economy. The Powertrain Control Module (PCM), is the heart of the control system.
This vehicle uses several electronic components which form an electronic computer network, designed to control various engine and body sub-systems. The heart of the computer network is the Body Computer Module (BCM). The BCM has an internal microprocessor which is the center for communication with all the other components, and controls the on-board diagnostics of the vehicle. All system sensors and switches are monitored by the BCM or one of the five other major components that complete the computer system network. The other five components are the Climate Control Driver Information Center (CCDIC), Diagnostic Energy Reserve Module (DERM) Supplemental Inflatable Restraint (SIR) controller, Powertrain Control Module (PCM), Heating, Ventilation, and Air Conditioning (HVAC) Programmer, and the Instrument Panel Cluster (IPC).
ON-BOARD DIAGNOSTICS SYSTEM OPERATION
This vehicle is equipped with an extensive on-board diagnostic system which is capable of detecting and compensating for faults, alerting the operator of a fault and recording pertinent data during the failure. It is also capable of displaying information about current vehicle performance when a fault occurred.
In order to access and control the self diagnostics features available, additional electronic components are utilized by the service technician. The Climate Control Driver Information Center (CCDIC) provides displays and keyboard switches.
The display and keyboard information is transmitted over a single wire data circuit which carries the coded data messages back and forth between the different control computers. and the CCDIC. This communications process allows the appropriate computer to transfer any of its available diagnostic information to the appropriate panel for display during service. By depressing appropriate buttons on the CCDIC, data messages are requested to be displayed. The diagnostics mode indicators on the CCDIC are used to indicate system operating modes. The different modes of operation are indicated by the status indicator either being turned "ON" or turned "OFF".
SELF DIAGNOSTICS
Climate Control Driver Information Center:
The CCDIC is used by the driver to control the air conditioner and heating system, also used to retrieve diagnostic information (i.e. trouble codes, sensor parameters, etc.), or override certain output components. The DERM monitors, detects, and records the SIR system during operation when system components malfunction, stores the malfunction as a trouble code, and maintains a 36 volt loop reserve energy supply to provide deployment energy in the event the vehicle voltage is low or lost during an accident. The PCM controls the fuel and ignition systems to obtain good performance and low exhaust emissions. The IPC is used to display information to the driver such as vehicle speed, engine rpm, and fuel level. The HVAC Programmer receives information from the CCDIC and carries out the commands necessary to obtain the correct interior temperature.
SELF-DIAGNOSTICS:
In addition to the PCM, the vehicle contains a Body Computer Module (BCM) which is used to control various vehicle functions based on sensors and switch inputs.
The PCM has the capability to diagnose faults in the sensors, input switches, components and systems they control. When the PCM recognizes a problem, it may turn "ON" the "Service Engine Soon" MIL on the instrument panel or send a message to the BCM to turn "ON" the "SERVICE ENGINE SOON" message on the CCDIC to alert the driver that a malfunction has occurred or the PCM may send a message to the IPC to turn "ON" the "Service Vehicle Soon" message on the CCDIC.
Serial Data (CKT 800) Line:
SERIAL DATA
All components in the system (PCM, BCM, IPC, CCDIC) are always in continuous communication with each other to provide accurate control over the many sub-systems involved. When one or more of these sub-system circuits exceeds pre-programmed limits a malfunction is indicated by a service engine soon warning lamp, and a backup function may be activated until the malfunction is corrected. The communications line is a single circuit (CKT 800) which is referred to as the data line or serial data line.
ADDITIONAL SYSTEMS:
Torque Management - is a function of the PCM that reduces engine power under certain conditions. Torque management is used to prevent overstress of powertrain components, to limit engine power when brakes are applied, and to prevent vehicle damage during certain abusive maneuvers. The PCM uses manifold vacuum, intake air temperature, spark retard, engine speed, engine coolant temperature, A/C clutch status, and EGR valve position to calculate engine output torque. The system uses the anti-lock brake system circuits and hardware for operation.
Traction Control - is a function of the PCM and the EBTCM that reduces front wheel slip during acceleration by applying the front brakes and reducing engine power. The EBTCM may decide to apply the front brakes only or apply the front brakes and request reduced torque output from the powertrain. The PCM may respond by shutting off fuel to one or more cylinders depending on the percent torque reduction requested.