Part 2
Inertia Fuel Shutoff (IFS) SwitchInertia Fuel Shutoff (IFS) Switch:
The purpose of the IFS switch is to shutoff the fuel pump if a collision occurs. It is located in the passenger side kick panel and it consists of a steel ball held in place by a magnet. When an impact occurs, the ball breaks loose from the magnet, rolls up a conical ramp and strikes a target plate which opens the electrical contacts of the switch and shuts off the electric fuel pump in the fuel conditioning module. Once the switch is open, it must be manually reset before restarting the vehicle. To reset the IFS switch, the button on top of the switch must be pushed down.
Intake Air Temperature (IAT) Sensor
The IAT sensor is a thermistor device. The electrical resistance of a thermistor decreases as the temperature increases, and resistance increases as the temperature decreases. The varying resistance affects the voltage drop across the sensor providing a signal corresponding to temperature. The IAT is integrated with the mass air flow (MAF) sensor, known as the MAF/IAT sensor.
Intake Air Temperature 2 (IAT2) Sensor
Intake Air Temperature 2 (IAT2) Sensor:
The IAT2 sensor is a thermistor device. The electrical resistance of a thermistor decreases as the temperature increases, and resistance increases as the temperature decreases. The varying resistance affects the voltage drop across the sensor providing a signal corresponding to temperature.
The IAT2 sensor is located in the intake manifold. The sensor provides a manifold air temperature signal to the PCM. The PCM uses the IAT2 signal to control timing and fuel rate during cold starts and provide an input to the cold idle kicker.
Intake Throttle
Intake Throttle:
The intake throttle modifies the intake airflow from the charge air cooler (CAC) into the exhaust gas recirculation (EGR) mixing elbow and into the intake manifold. The intake throttle uses an electric motor to open and close a throttle plate, based upon inputs from the PCM. The intake throttle actuator is a smart device, which is controlled by a pulse width modulated (PWM) signal to attain the desired position using the ITVC (control) circuit. The intake throttle actuator determines the gains and control for the desired position. The desired position is between 5% and 95%.
The intake throttle actuator signals the intake throttle plate status to the PCM using the ITVF (feedback) circuit. If the feedback signal is 12 volts, the throttle plate is at the desired position. If the feedback signal is low, a DTC is set indicating the throttle plate is not at the desired position or is out of range. The feedback signal does not indicate actual throttle plate position.
The intake throttle is used only during diesel particulate filter regeneration events for air/fuel ratio control.
Manifold Absolute Pressure (MAP) Sensor
Manifold Absolute Pressure (MAP) Sensor:
The MAP sensor is a variable capacitor sensor that is supplied a 5-volt reference signal by the PCM and returns a voltage signal to the PCM relative to the intake manifold pressure. The sensor voltage increases as the pressure increases. The MAP sensor allows the PCM to determine the engine boost to calculate fuel quantity. In addition, the MAP signal is used to control smoke by limiting fuel quantity during acceleration until a specified boost pressure is obtained, and is used by the PCM for EGR system calculations and control.
A MAP signal concern (an incorrect signal from the MAP sensor), when detected by the PCM, results in the PCM using an estimated, calculated manifold pressure that is derived from known engine conditions in place of the signal from the sensor.
An open or short in the MAP sensor wiring results in an out of range high or low voltage, at the PCM.
The output of the sensor ranges from 0.175 volts at 28.6 kPa (4.15 psi) to 4.825 volts at 616.5 kPa (89.42 psi). At an atmospheric pressure of 101 kPa (14.65 psi) the output of the sensor is between 0.67 and 0.82 volt.
Mass Air Flow (MAF) Sensor
Mass Air Flow (MAF) Sensor:
The MAF sensor provides a signal to the PCM proportional to the intake air mass. The MAF sensor uses a hot wire sensing element to measure the amount of air entering the engine. The hot wire is maintained at a constant temperature above ambient. Air passing over the hot wire cools the wire. The current required to maintain the temperature of the hot wire is proportional to the air flow.
The MAF sensor is a digital sensor that provides an output signal of varying frequency. The signal's time period is proportional to the flow rate crossing the sensor. The greater the air flow the greater the time period. The time period varies from 130 microseconds (15 kHz) at a low flow or idle condition, to 530 microseconds (1.9 kHz) at a high flow rate condition. If the sensor element is broken the diagnostic mode default output of the sensor will be 4650 microseconds (215 Hz).
Power Take-Off
The power take-off (PTO) system provides an input signal to the PCM indicating there is an additional load being applied to the engine. The PCM disables the on-board diagnostic (OBD) monitors and increases the engine RPM based on the PTO system or auxiliary idle control input.
Turbocharger
Turbocharger (Part 1):
Turbocharger (Part 2):
The turbocharger assembly is an exhaust-driven centrifugal compressor. Expanding exhaust gases drive the turbine shaft assembly to speeds over 100,000 RPM. The two stage variable turbocharger geometry is controlled by the turbocharger actuator.
Turbocharger Actuator
Turbocharger Actuator:
The turbocharger actuator has internal diagnostics capability and sends information to the PCM for DTC generation. The PCM monitors and controls the turbocharger geometry using the CAN. The turbocharger actuator controls the turbocharger geometry using an external mechanical linkage arm from the actuator to the turbocharger. The turbocharger actuator is used to continually adjust the vanes of a turbocharger. By adjusting the vanes, the exhaust gas flow can be routed to the turbine wheel at optimum efficiency.
The turbocharger actuator is cooled using the fuel cooling system to maintain a temperature below 145°C (293°F). The turbocharger actuator will not respond to PCM commands when its internal temperature is greater than 145°C (293°F) and a DTC is set. When the internal temperature falls below 135°C (275°F) the turbocharger actuator resumes normal operation.
The PCM reduces engine torque when the actuator temperature or engine coolant temperature is too high.