Instructor Name Your Name 13 CHAPTER Learning Objectives Explain the concept of virtual fusing List the type of inputs and outputs used by a typical body control module Discuss the reasons that most electronic control modules used in modern trucks make use of a reference ground ID: 196486
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Body Control Modules
Instructor Name: (Your Name)
13
CHAPTERSlide2
Learning Objectives
Explain the concept of virtual fusingList the type of inputs and outputs used by a typical body control moduleDiscuss the reasons that most electronic control modules used in modern trucks make use of a reference groundDiscuss the difference between a conventional switch and diagnosable switchDescribe how a body control module can act as a turn signal flasherSlide3
Learning Objectives (continued)
Retrieve DTC’s stored in memory related to the body controllerList the main components of the International Diamond Logic® and Freightliner® Smart Plex™ multiplexed electrical systemsDescribe how a Freightliner Smart Switch operatesExplain the concept of ghost voltage and describe how it can lead to confusion when diagnosing an electrical problemSlide4
International Multiplexed Electrical System
Referred to as the Diamond Logic electrical systemBetween 2001-2006 body control modules were referred to as electrical system controller (ESC)In 2007 the name was changed to the body controllerSlide5
International ESC
Figure 13-1 International electrical system controller (ESC).Slide6
International Body Controller
Figure 13-2 International body controller.Slide7
Overview of Body Controller
Figure 13-3 Overview of body controller.Slide8
Tech Tip
Think of the J1939 data link as both being an input and an output device for most electronic devices. The messages received by a module are inputs; the messages sent by a module are the outputs.Slide9
Typical Body Control Module Horn Circuit
Figure 13-5 Typical body control module horn circuit.Slide10
Body Controller OutputsThe body controller has three main types of outputs:
High side driversLow side driversMessages transmitted on the J1939 data linkSlide11
High Side DriverCapable of sourcing high levels of current
The high side drivers used in body controllers are power MOSFETs (FETs)Some FETs are capable of sourcing 20A continuouslySmart FETs can monitor the amount of current that the FET is conductionSlide12
Current Feedback For Virtual Fusing
Figure 13-6 The high side driver measures the current being conducted and feeds back this information to the microprocessor as a proportional voltage.Slide13
Low Side DriversCurrent ratings of 1A or less
Commonly used in body controllersLow side drivers sink a path to groundTypically used to energize relay coils or small solenoids Slide14
Body Controller InputsThere are three main types of inputs to the body controller:
Hardwired inputs from switches and sensorsMessages received from a proprietary switch data linkMessages received from the J1939 data linkSlide15
Hardwired InputsConventional switch to control electrical devices
Reference ground is a single ground that all sensors and switches shareReference ground is connected to chassis ground but in one location usually inside the electronic moduleSlide16
Common Reference Ground Located in Body Controller
Figure 13-7 The common reference ground point inside of body controller is connected to chassis ground at only one location.Slide17
CAUTION
It is vital that any electronic system that uses a reference ground only be grounded in accordance with OEM recommendations. Even though reference ground may appear to be the same as chassis ground, connecting the reference ground to chassis ground outside the electronic module may result in the truck having intermittent EMI induced problems that are nearly impossible to duplicate or troubleshoot.Slide18
Open and Closed Switches with Digital Input
Figure 13-8 Open switch (upper) and closed switch (lower) with digital input.Slide19
Open Circuit Prevents Digital Input From Detecting Switch is Closed
Figure 13-9 Open circuit prevents digital input from detecting that switch is closed; input voltage should be 0V with switch closed, but is actually +12V.Slide20
Diagnosable Switch With Contacts Open and Closed
Figure 13-10 Diagnosable switch with contacts open and closed. Slide21
Diagnosable Switch Open;8V at the Input Terminal
Figure 13-11 Diagnosable switch open; 8V at input terminal.Slide22
Diagnosable Switch Closed; 6V at the Input Terminal
Figure 13-12 Diagnosable switch closed; 6V at input terminal.Slide23
Diagnosable Switch Open Circuit; 12V at the Input Terminal
Figure 13-13 Diagnosable switch open circuit; 12V at input terminal.Slide24
Switch PacksInternational trucks with body controllers use switch packs using J1708/J1578 specification data link
This proprietary link is not the same as the J1708/J1587 data link connected to the power train or ECM modulesSwitch packs are rockers that require switch actuators installed in themSlide25
Switch Pack with Switch Actuators Removed
Figure 13-14 Switch pack with the switch actuators removed.Slide26
Tech Tip
Think of high side drivers as being like conventional relays. A small signal provided by the microprocessor is used to control a large amount of current.Slide27
Body Controller Headlight Circuit
Figure 13-15 Body controller headlamp circuit. EGC contains headlamp switch.Slide28
Turn-Signal System, International Truck With Body Controller
Figure 13-16 Turn-signal system on International trucks with body controller. Two switches are inputs; four high side drivers are outputs.Slide29
Tech Tip
The body controller only powers the applicable trailer light relay control circuit. The body controller does not directly supply the current to the trailer lighting. A conventional CPD such as a fuse or a circuit breaker in the PDC is used to protect the trailer wiring, not virtual fusing.Slide30
A/C System Inputs; Outputs Is A/C Clutch High Side Driver
Figure 13-17 Air conditioning system inputs; output is A/C clutch high side driver.Slide31
Cruise Control Related Inputs Output is J1939 Message to Engine ECM
Figure 13-18 Cruise control related inputs; output is J1939 message to engine ECM.Slide32
Primary and Secondary Air Pressure Measurement System
Figure 13-19 Primary and secondary air pressure measurement system.Slide33
Windshield Wiper System Outputs
Figure 13-20 Windshield wiper system outputs; one high side driver and two low side drivers.Slide34
Wiper Switch Inputs and Truth Table
Figure 13-21 Wiper switch inputs and truth table.Slide35
Tech Tip
An open windshield wiper switch connection on an International truck with a body controller causes the wiper to operate at high speeds at any time the key switch is in the ignition position. Additionally, a short to ground of the windshield washer pump control circuit will cause the windshield wipers to operate at low speed any time the key switch is in the ignition position because the controller is falsely detecting that the washer switch is depressed.Slide36
Freightliner Multiplexed Electrical System
Freightliner refers to their multiplexed electrical system as SmartPlex™The bulkhead module (BHM) acts as the primary command module for body and chassis electrical systems.The chassis module (CHM) is the other standard electronic moduleThe CHM is a slave or dependent that receives commands from the BHMSlide37
Freightliner SmartPlexTM Electronic Module Locations
Figure 13-22 Freightliner SmartPlexTM electronic module locations.Slide38
Bulkhead Module (BHM)
Main electronic controller for Freightliner SmartPlexTM electrical systemThe BHM is connected to the J1939 data link and transmits and receives information from other electronic modulesThe BHM is hardwired to several inputs in the cabDirect hardwired high side outputs include horn, dome light, left side low-beam and high beam headlightsSlide39
Freightliner Smart Switch Schematic
Figure 13-25 Freightliner smart switch schematic.Slide40
Chassis Module (CHM)Contains several high side driver FETs that source current to several chassis electrical features
The CHM is dependent on commands from the BHM via the J1939 data linkHigh side driver outputs include park and marker lights, back-up lamps, turn signal lamps, right side high and low beam headlights and fog lampsSlide41
Freightliner Multifunction Switch
Figure 13-28 Freightliner multifunction switch.Slide42
Freightliner Multiplexed Headlamp Control
Figure 13-29 Freightliner multiplexed headlamp control.Slide43
Troubleshooting The Multiplexed Truck
Best if performed with OEM diagnostic software and a PC, referred to as a electronic service tool (EST)Software for Freightliner trucks is ServiceLink® Software for International trucks is diamond Logic®This software permits viewing diagnostic trouble codes by the body controller and EGC, along with fault descriptionsSlide44
International Diagnostic Code Retrieval
Place the ignition switch in the ignition or accessory positionSet the park brakeDepress the cruise control ON and RESUME switches at the same timeThe EGC will indicate the number of DTCs that existSlide45
Diagnostic Trouble Codes Display
Figure 13-32 Diagnostic trouble codes as displayed in instrument panel cluster odometer display.Slide46
SAE J1939 Suspect Parameter Number
Figure 13-33 SAE J1939 suspect parameter number (SPN).Slide47
SAE J1939 Failure Mode Indicator
Figure 13-34 SAE J1939 failure mode indicator.Slide48
ORH Condition at a Pulled-Up Input With Open Circuit
Figure 13-36 ORH condition at a pulled-up input with an open circuit.Slide49
ORL Condition at a Pulled-Up Input with Grounded Circuit
Figure 13-37 ORL condition at a pulled-up input with a ground circuit.Slide50
ORL Condition at a Pulled-Down Input With Open Circuit
Figure 13-38 ORL condition at a pulled-down input with an open circuit.Slide51
SummaryThe body control module on International High Performance Vehicles is called the electrical system controller (ESC) on model year 2001-2006 trucks and the body controller on 2007 and later year trucks. The body controller or ESC contains a microprocessor. The body controller or ESC uses information obtained from input sources to control the
outputs.Slide52
Summary(continued)
Outputs of the body controller include high side drivers, low side drivers, and messages on the J1939 data link.Input sources for the body controller include messages from the J1939 data link, messages from the switch link, and hardwired inputs such as switches and sensors.A reference ground scheme is commonly used in automotive electronics to minimize the effects of electromagnetic interference and to improve measurement accuracy for sensor circuits.Slide53
Summary(continued)
A diagnosable switch is a special switch that provides specific values of resistance, unlike a conventional switch, which is either an open circuit or a near 0Ω. A diagnosable switch is connected to an analog input. This permits circuit failures such as an open circuit or a shorted-to-ground circuit to be diagnosed. Slide54
Summary(continued)
The body controller controls several electrical system features, including headlamps, turn signals, stop lamps, and windshield wipers. The various switches act as inputs to the body controller through either hardwiring or multiplexing. The body controller microprocessor makes decisions based on its programming and provides an output in the form of energizing a high side driver, energizing low side driver, or transmitting a data link message.Slide55
Summary(continued)
Self-diagnostics assists in troubleshooting the body controller. Diagnostic trouble codes may be logged to indicate a circuit that is out of range high or out of range low.The Freightliner SmartPlexTM system uses two or more separate modules to control body electrical features. The bulkhead module (BHM) controls the chassis module (CHM) via the J1939 data link.Slide56
Summary(continued)
The Freightliner SmartPlexTM uses optional smart switches to control electrical system features. Each smart switch contains two identification resistors that uniquely define the switch function.The instrument cluster in the Freightliner SmartPlexTM system is called the ICU. The ICU acts as the input device for the stalk mounted multifunction switch. The ICU transmits the status of the multifunction switch inputs on the J1939 data link.Slide57
Summary(continued)
Diagnostic trouble codes (DTCs) are used to indicate that an electrical module has detected and abnormal condition. DTCs may indicate a sensor in-range operating condition, such as engine coolant temperature is too high. DTCs may also indicate sensor out of range conditions, such as open circuits or shorts to grounds. A J1939 DTC consists of an SPN and FMI.Slide58
Summary(continued)
Ghost voltage describes an open circuit measurement of a voltage by a DMM in a circuit with high resistance. Ghost voltage can result in misdiagnosis.