Diesel Powertrain Control Module (PCM) Inputs
DIESEL POWERTRAIN CONTROL MODULE (PCM) INPUTSAccelerator Pedal Position (APP) Sensor
The APP sensor is a 3-track potentiometer that is used to calculate driver demand for fuel quantity. The sensor receives a VREF voltage from the PCM and provides a variable voltage signal directly proportional to the accelerator pedal position.
A detected malfunction of the APP sensor illuminates the electronic throttle control (wrench) indicator. A PCM detected fault on one of the 3 sensor signals permits normal engine operation. A fault with 2 sensor signals only allows the engine to operate at idle.
Air Conditioning (A/C) Pressure Switch
A/C Pressure Switch:
The A/C pressure switch is used for additional A/C system pressure control. The A/C pressure switch is also referred to as the refrigerant containment switch.
For refrigerant containment control, the normally closed high pressure contacts open at a predetermined A/C head pressure. This turns off the A/C by opening the A/C demand circuit, preventing the A/C pressure from rising to a level that would open the A/C high pressure relief valve.
Barometric Pressure (BARO) Sensor
Barometric Pressure (BARO) Sensor:
The BARO sensor is a variable capacitor sensor that processes a signal indicating atmospheric pressure. This allows the PCM to compensate for altitude. The PCM uses this information to calculate injection timing and glow plug control. The BARO sensor is located behind the lower steering column opening finish panel.
A BARO sensor fault results in an out-of-range signal to the PCM.
Brake Pedal Position (BPP) Switch
Brake Pedal Position (BPP) Switch:
The BPP switch signals the PCM with a battery positive voltage (B+) signal whenever the vehicle brake pedal is applied.
The signal informs the PCM to disengage the torque converter clutch, speed control, and auxiliary idle control (if equipped).
If all the stoplamp bulbs are burned out (open), a high voltage is present at the PCM due to a pull-up resistor in the PCM. This provides fail-safe operation in the event the circuit to the BPP switch has failed.
Brake Pressure Applied (BPA) Switch
Brake Pressure Applied (BPA) Switch:
NOTE: The BPA switch is present on vehicles equipped with speed control.
All vehicles have a single BPA switch. A BPA switch provides a backup for the brake pedal position (BPP) switch. Normally, a brakes-applied signal from the BPP switch disengages the speed control. If the BPP switch signal is lost, the BPA switch then supplies the brakes-applied signal to the speed control system. The BPA switch signal is also used in the transmission strategy and the key on engine running (KOER) self-test.
Camshaft Position (CMP) Sensor
Camshaft Position (CMP) Sensor:
The CMP sensor is a variable reluctance sensor, which responds to a rotating trigger protruding from the camshaft. The trigger is a single 9.525 mm (0.375 inches) diameter peg approximately 18 degrees wide, projecting 3-5 mm (0.12-0.20 inches) from the camshaft. The sensor produces a sine wave in response to the peg as it passes the sensor. The sensor output is required to determine the camshaft position.
Clutch Pedal Position (CPP) Switch
The CPP switch provides an input to the PCM indicating the clutch pedal position. The CPP switch A is a normally open switch that indicates clutch disengagement (bottom of travel). CPP switch B is a normally closed switch that indicates clutch engagement (top of travel).
Cold Idle Kicker
The cold idle kicker provides an increase in idle speed during cold engine warm up, of up to 1,100 RPM (normally 725 RPM for manual, 690 RPM for auto), for a faster warm-up to operating temperature during extended idle conditions. This is accomplished by the PCM, which monitors the engine oil temperature (EOT) sensor input and adjusts the RPM accordingly, to a maximum of 1,100 RPM.
The idle speed is increased proportionately when the engine oil temperature is less than 70°C (158°F) and the engine has been at idle for more than 2 minutes. Applying the brake pedal, clutch or accelerator pedal deactivates the cold idle kicker and returns the idle speed to 690 RPM.
Allowing the engine to idle for more than 5 minutes with the EGR valve commanded closed, the variable geometry turbocharger duty cycle may step from 15% to 85%. This occurs momentary and repeats after a calibrated time. For additional information, refer to Vane Sweep.
Crankshaft Position (CKP) Sensor
Crankshaft Position (CKP) Sensor:
The CKP sensor is a variable reluctance sensor which responds to a rotating actuator positioned on the crankshaft. The actuator is a 60-2 tooth steel disk with 58 evenly spaced teeth and a minus 2 tooth slot. The sensor produces a sine wave for each tooth edge of the actuator. The sensor output is required to determine crankshaft speed, position, and acceleration.
Diesel Engine Power Monitor (DEPM)
The DEPM strategy resides in the transmission control module (TCM) located inside of the PCM. The function of the DEPM is to monitor the engine RPM when there is no power demand from the APP sensor.
Under normal engine idle operation, the DEPM value must always be higher than the engine RPM. In the event that the RPM does increase to its calibrated idle speed value following completion of deceleration fuel shutoff due to the injectors not turning off, the DEPM disables the crank and cam output signals sent by the PCM to the fuel injection control module (FICM). The fuel injection control module monitor (FICMM) input line informs the DEPM when the injectors are turned on and when the injectors are turned off. When the FICMM line is either shorted or open, the monitor strategy assumes that the fuel injectors are always turned on and sets a DTC.
Engine Coolant Temperature (ECT) Sensor
Engine Coolent Temperature (ECT) Sensor:
The ECT sensor is a thermistor device in which resistance changes with temperature. 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 terminals and provides electrical signals to the PCM corresponding to temperature.
If the PCM receives a high engine temperature signal from the ECT, it adjusts fueling rates to protect the engine from damage due to overheating.
Engine Oil Temperature (EOT) Sensor
Engine Oil Temperature (EOT) Sensor:
The EOT sensor is a thermistor whose resistance decreases as engine oil temperature increases. The EOT signal is used by the PCM to calculate fuel quantity, injection timing, and glow plug operation.
At low ambient air temperatures and an oil temperature of less than 70°C (158°F) low idle is increased to maintain stable idle quality. Fuel quantity and timing is controlled throughout the total operating range to provide adequate torque and power.
An EOT signal detected out of range, high or low, by the PCM causes the PCM to substitute a temperature based on the ECT to be used for operating purposes.
Exhaust Pressure (EP) Sensor
Exhaust Pressure (EP) Sensor:
The EP sensor is a variable capacitor sensor that is supplied a 5-volt reference signal by the PCM and returns a linear analog voltage signal that indicates pressure. The EP sensor measures the pressure in the LH exhaust manifold. The sensor feedback signal is used for variable geometry turbo (VGT) and exhaust gas recirculation (EGR) valve control.
An open or short in the EP sensor wiring results in an out-of-range low voltage at the PCM.
Fan Speed Sensor (FSS)
The FSS is a Hall effect sensor integral to the visctronic drive fan (VDF). The PCM monitors the sensor input and controls the VDF speed based upon the engine coolant temperature (ECT), the transmission fluid temperature (TFT), and the intake air temperature (IAT) requirements. When an increase in fan speed for vehicle cooling is requested, the PCM monitors the FSS signal and outputs the required pulse width modulated (PWM) signal to a fluid port valve within the VDF.
Injection Control Pressure (ICP) Sensor
Injection Control Pressure (ICP) Sensor:
The ICP sensor is a variable capacitor sensor that is supplied a 5-volt reference signal by the PCM and returns a linear analog voltage signal that indicates pressure. The sensor measures the oil pressure in the oil rail and the PCM uses this information to determine injection control pressure. The ICP sensor along with the injection pressure regulator (IPR) form a closed loop fuel pressure control system.
If the PCM detects an inoperative ICP sensor, the PCM controls the injection control pressure from a PCM estimated injection control pressure.
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 6.0L diesel uses 2 IAT sensors. For vehicles with a mass air flow (MAF) sensor, the IAT sensor is integrated into the MAF sensor. For vehicles without a MAF sensor, the IAT sensor is a stand alone sensor.
Intake Air Temperature 2 (IAT2) Sensor
Intake Air Temperature 2 (IAT2) Sensor:
The IAT2 or manifold air temperature (MAT) 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.
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 fault detected by the PCM causes the PCM to calculate an estimated manifold pressure based on known engine conditions.
Mass Air Flow (MAF) Sensor
F-Super Duty Mass Air Flow (MAF) Sensor:
Mass Air Flow (MAF) Sensor (E-Series):
The MAF sensor provides an analog voltage 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 200°C (392°F) above the ambient temperature. 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 mass flow. The MAF signal is used to calculate the exhaust gas recirculation (EGR) and for fault detection.
Output Shaft Speed (OSS) Sensor
Output Shaft Speed (OSS) Sensor:
The OSS sensor detects the speed of the transmission output shaft. The sensor uses variations in a magnetic field caused by a tone wheel to generate a pulse train output corresponding to shaft speed. The OSS tone wheel uses a repetitive pattern of 3 different angular displacements between the teeth. The pulse width order can be used to determine the shaft rotation direction. The magnetic sensor element may be a Hall effect sensor or a magneto-resistive pick-up. Due to the open collector design and the RC timing involved in the pull-up, the rising edge of the pulse train is not a reliable edge for critical timing, only the falling edge. The pull-up is located in the PCM to provide a wetting current for the sensor connectors. This applies specifically to the automatic transmission.
Parking Brake Switch
The parking brake switch signal indicates when the parking brake is applied. On all vehicles, the parking brake switch is located under the instrument panel. The parking brake switch signal deactivates the speed control if the brake is applied during speed control operation and provides a brake input for the cold idle kicker.
Transmission Control Switch (TCS)
Typical Column-shaft Transmission Control Switch (TCS):
On automatic transmission equipped vehicles, the TCS provides an input signal to the PCM whenever the switch is pressed. For F-Super Duty, the tow/haul indicator illuminates when the TCS is cycled to engage and disengage the tow/haul strategy. For E-Series, the overdrive cancel indicator illuminates when the TCS is cycled to engage or disengage the overdrive function of the transmission.
4x4 Low Switch
The 4x4 low switch provides a signal to the instrument cluster when 4x4 low is selected. This input is used to adjust the shift schedule. Using the controller area network (CAN) (F-Super Duty) the instrument cluster provides a four wheel drive (4WD) status signal to the PCM.