Understanding Computer Control Systems Electrical 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

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)

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

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

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

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

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.

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.

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

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

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

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

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

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

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

Understanding Computer Control Systems Examples of Common SAE J1708 Subsystem Identification - SID SID 213 PLC Data Link SID 231 SAE J1939 Data Link SID 232 5 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

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

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

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