1. Understanding Computer Control Systems
Electrical 2

2. Understanding Computer Control Systems
Processing system
Input
Sensors
Switches
Data bus CAN or OBD
Processing
Electronic Control Module (ECM)
Parameters, setting and programming
Output
Solenoids
Data bus CAN or OBD
MIL lights
Motors or Actuators

3. Understanding Computer Control Systems
Switches
Key
Cruise
On off
Set resume
Retarder
Level
Brake
Service (some systems will utilize 2)
Park
Switches
Interlock
PTO
Door
Throtle
Idle Validation Switch (IVS)

4. Understanding Computer Control Systems
Temperature
Thermistor
Thermocouple
Negative Temperature Coefficient (NTC)
Positive Temperature Coefficient (PTC)
Two wire
Passive sensor
Three wire
Active sensor
Used for
Water temp
Oil temp
Air temp
Ambiant
Manifold
EGR
Pre cooler
Post cooler
Fuel temp
Cabin temp

5. Understanding Computer Control Systems
Pressure (piezo)
Piezoresistive
Standard on Detroit, Caterpillar, and Volvo-Mack
Piezoelectric
Standard on Cummins and some heavy equipment
YouTube on Piezoelectric
Mechanical
Older electrical gauges
Used for
Oil pressure
Engine lube
HEUI action
Hydraulic
Fuel pressure
Primary
Secondary
Air Pressure
Manifold
Atmospheric

6. Understanding Computer Control Systems
Speed and position
Permanent magnet
Hall effect
Potentiometer
Used for
Wheel speed
Crankshaft
Camshaft
Fuel pump
Actuators
Vehicle speed
Throttle
Accessories

7. Understanding Computer Control Systems
Databus
Automotive
OBD I
Vehicle manufacture sets standard
OBD II
Current
Heavy duty
CAN
J1587 or J1787
J1939 or J1922
Proprietary link

8. J1587
Established in 1988 has a baud rate of 9600 this is still utilized for connection of service tools. These wires were called the twisted pair the wires was twisted together to reduce interference.

9. J1939
J1939 communicates at a 256,000 baud rate this is still used today. This utilizes high speed communication instead of being just a twisted pair it is shielded and utilize terminating risistors to make the communication a constant cyclical rather than linier.

10. Connectors
With just the J1587 you will utilize the 6 pin on the left and with J1922 and newer you will utilize the 9 pin on the right

11. Understanding Computer Control Systems
Processor
Electronic Control Module (ECM)
Programming and Parameters
Settings
ECM used on
SRS
ABS/ATC
Engine
Transmission
Dashboards
Power trains

12. Understanding Computer Control Systems
Solenoids
Actuators for
Injection
Retarder oil flow
Pneumatic fans
Hydraulics
Starting aids
EGR
Intake Valve Actuators or Variable Valve Actuators

13. Understanding Computer Control Systems
Malfunction Indicator Lamp
MIL
Shutdown Engine Lamp
SEL
Check Engine Lamp
CEL
Antilock Brakes
ABS
Automatic traction Control
ATC
Transmission
Automated
Automatic

14. Understanding Computer Control Systems
Motors/Actuators
Electronic over Mechanical pumps
Emissions
EGR
Variable Nozzle Turbo
VNT
Variable Geometry Turbo
VGT

15. Understanding Computer Control Systems
Diagnostic Trouble Codes
DTC
Flash codes or proprietary codes
SAE codes
Message Identifier
MID
Parameter Identifier
PID
System Identifier
SID
Component Identifier
CID
Utilizes only one of the following PID, SID, or CID
Failure mode Identifier
Active
Currently occurring
Can not be cleared
Historic
Is a record of a code
Can normally be cleared some require a password

16. Understanding Computer Control Systems
Examples of Common SAE J1708 Message Identification - MID MID 128 Engine
MID 130 Transmission
MID 136 Brakes, Power Unit - ABS MID 140 Instrument Cluster
MID 144 Cruise Control / Vehicle Control Unit
MID 146 Cab Climate Control
MID 150 Suspenstion, Power Unit MID 166 Tires, Power Unit
MID 177 Particulate Trap System
MID 181 Communication Unit, Satellite
MID 200 Auxillary Cab Climate Control MID 216 Light Control Administrator Unit
MID 232 Safety Restraint System
MID 249 Body Controller
Examples of Common SAE 1708 Parameter Identification - PID PID 8 Brake system air pressure Low warning switch statuts
PID 12 Brake Stroke Status
PID 27 Percent Exhaust Gas Recirculation Valve #1 Postision
PID 51 Throttle Postion PID 80 Washer Fluid Level
PID 81 Particulate Trap Inlet Pressure
PID 84 Road Speed
PID 91 Percent Accelerator Pedal Position
PID 94 Fuel Delivery Pressure
PID 97 Water In Fuel Indicator
PID 98 Engine Oil Level f

17. Understanding Computer Control Systems
Examples of Common SAE J1708 Subsystem Identification - SID
SID 213 PLC Data Link
SID 231 SAE J1939 Data Link
SID Volts DC Supply
SID 250 SAE J1708/J1587 Data Link
SID 251 Power Supply
Examples of Common SAE J1708 Failure Mode Identifiers - FMI
FMI 0 Data Valid but above normal operational range
FMI 1 Data Valid but below normal operational range
FMI 2 Data Erratic
FMI 3 Voltage above normal - Shorted High
FMI 4 Voltage below normal - Shorted Low
FMI 5 Current below normal - Open Circuit
FMI 6 Current above normal - Grounded Circuit
FMI 7 Mechanical System Fault
FMI 8 Abnormal Frequency
FMI 9 Abnormal Update Rate
FMI 10 Abnormal Rate of Change
FMI 11 Failure Mode not Identified
FMI 12 Bad Device
FMI 13 Out of Calibration
FMI 14 Special Instructions

18. Understanding Computer Control Systems
Reading codes
Flash Codes
Utilizes equipment
Switches
Lights
Different procedure for different equipment
Dedicated switches
Other switches
Diagnostic Data Reader
OEM specific
Generic
Personal computer
Generic
OEM
Insite
Electronic Technician
Detroit Diagnostic Data Link

19. Understanding Computer Control Systems
Strategy Based Diagnostics (SBD)
Verify customer complaint
Quick check vehicle
Check DTC and history
Check TSB’s
Follow the service manual troubleshooting
Analyze and record DTCs
Clear codes
Recheck DTCs
Determine course of action

20. Understanding Computer Control Systems
Return

21. Understanding Computer Control Systems
Return

22. Return