The VECU also monitors the position or state of a number of switches to perform its control and diagnostic functions. They are:
EGR Differential Pressure Sensor EGR Temperature Sensor A/C Pressure Switch Engine Coolant Level (ECL) Sensor Air Suspension Height Control Switch Engine Coolant Temperature (ECT) Sensor Clutch Switch Engine Oil Pressure (EOP) Sensor Differential Lock Switch Engine Oil Level (EOL) Sensor Engine Oil Temperature (EOT) Sensor DRL Override Switch Exhaust Temperature Sensor (DPF Sensors) Engine Brake Switches Fan Override Switch Ignition Key Switch Fuel Pressure Sensor PTO Switches (if equipped) Intake Air Temperature And Humidity (IATH) Sensor Service and Park Brake Switches Intake Manifold (Boost) Temperature Sensor Shutdown Override Switch Throttle Position (TP) Sensor Speed Control Switches (Set/Decel, Resume/Accel) Turbo Speed Sensor Variable Geometry Turbo (VGT) Position Sensor 5th Wheel Slide Switch The Engine Management System (EMS) Module is bolted to a fuel cooled mounting plate which is on the left side of the engine on the air intake manifold.
The EMS is a microprocessor based controller programmed to perform fuel injection quantity and timing control, diagnostic fault logging, and to broadcast data to other modules. The fuel quantity and injection timing to each cylinder is precisely controlled to obtain optimal fuel economy and reduced exhaust emissions in all driving situations. The Vehicle Electronic Control Unit (VECU) and Engine Management System (EMS) Module are dependent on each other to perform their specific control functions.
In addition to switch and sensor data the broadcast of data between modules also includes various calculations and conclusions each module has developed, based on the input information it has received. Sensors The EMS controls the operation of the Electronic Unit Injectors (EUIs), engine brake solenoid, EGR valve, turbocharger nozzle position, and cooling fan clutch based on input information it receives over the serial data lines and from the following sensors: AMBIENT AIR TEMPERATURE SENSOR The Ambient Air Temperature Sensor is used to detect the outside air temperature. The sensor modifies a voltage signal from the ECM.
The modified signal returns to the ECM as the ambient air temperature. The sensor uses a thermistor that is sensitive to the change in temperature. The electrical resistance of the thermistor decreases as temperature increases. Ambient Air Temperature Sensor Ambient (Barometric) Pressure Sensor Boost Air Pressure (BAP) Sensor The Ambient Air Temperature Sensor is located in the left front of the vehicle. Camshaft Position (Engine Position) Sensor Cooling Fan Speed (CFS) Sensor Crankshaft Position (Engine Speed) Sensor Differential Pressure DPF Sensor Page 7 DESCRIPTION AND OPERATION