Part 1
ENGINE CONTROL COMPONENTSAccelerator Pedal Position (APP) Sensor
The APP sensor is a 2-track potentiometer that is used to calculate driver demand for power based on the rotation angle of the accelerator pedal. The sensor receives a reference voltage from the powertrain control module (PCM) and provides a variable voltage signal directly proportional to the accelerator pedal position. The PCM uses the 2 APP sensor inputs to calculate the desired fuel quantity, injection timing, and the correct fuel pressure. A concern with the APP sensor illuminates the powertrain malfunction indicator (wrench). Normal engine operation is permitted if the PCM detects a concern on one of the 2 sensor signals. If the PCM detects a concern on both of the sensor signals, the PCM only allows the engine to operate at idle.
Accelerator Pedal Position (APP) Sensor:
Air Filter Restriction Gauge
An electronic air filter restriction gauge is located in the air cleaner housing. The sensor is hardwired to the instrument cluster. When the air flow in the intake air system reaches the maximum allowable restriction limit, a switch in the air filter restriction gauge closes and a message is displayed in the message center of the instrument cluster.
Air Filter Restriction Gauge:
Boost Pressure Gauge
The boost pressure gauge is controlled by the instrument cluster. The PCM sends a message through the controller area network (CAN) to the instrument cluster indicating engine boost pressure.
Brake Pedal Position (BPP) Switch
The BPP switch signals the PCM with a battery positive voltage (B+) signal whenever the 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 Pedal Position (BPP) Switch:
Camshaft Position (CMP) Sensor
The CMP sensor is a variable reluctance sensor that responds to a rotating trigger protruding from the camshaft. The trigger is a single peg projecting from the camshaft. The peg passes the sensor once per camshaft revolution and produces a single pulse. The camshaft speed is calculated from the frequency of the CMP sensor signal. If the CMP sensor signal is lost while the engine is running, the engine continues to operate. The loss of the CMP signal while starting the engine will cause a no start condition.
Camshaft Position (CMP) Sensor:
Charge Air Cooler (CAC)
The CAC is composed of a radiator mounted in the grill of the vehicle and the tubing used to connect the output of the turbocharger to the intake of the engine. The CAC is designed to cool the induction air which has been heated by the turbocharger. As the heated air flows through the CAC, heat is transferred to the outside air reducing the temperature of the intake air.
Charge Air Cooler (CAC):
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).
Clutch Pedal Position (CPP) Switch:
Cooling Fan
The actuator valve controls the fluid flow from the reservoir into the working chamber. Once viscous fluid is in the working chamber, shearing of the fluid results in fan rotation. The valve is activated by a pulse width modulation (PWM) output signal from the PCM. By opening and closing the fluid port valve, the PCM controls the fan speed. Fan speed is measured through a Hall effect sensor, and is monitored by the PCM during closed loop operation. The PCM optimizes the fan speed based on the engine coolant temperature, the engine oil temperature, the fuel rail temperature, the transmission fluid temperature, the intake air temperature, or air conditioning requirements. When an increased demand for fan speed is requested for vehicle cooling, the PCM monitors the fan speed through the Hall effect sensor. If a fan speed increase is required, the PCM outputs the PWM signal to the fluid port, providing the required fan speed increase. During the key on, engine running (KOER) self-test, the PCM commands a 100% duty cycle. A DTC is set if the PCM detects the voltage on the valve control circuit is not within the expected range or if the fan speed is less than a calibrated value.
Cooling Fan:
Crankshaft Position (CKP) Sensor
The CKP sensor is a magnetic transducer mounted on the engine block, adjacent to a pulse wheel located on the crankshaft. The pulse wheel is a 60 minus 2 tooth steel disk with 58 evenly spaced teeth and a minus 2 tooth slot. As the crankshaft rotates, the CKP produces a sine wave for each tooth edge of the pulse wheel and it detects the missing 59th and 60th tooth. This configuration allows the CKP sensor to provide the PCM with the angular position of the crankshaft relative to a fixed reference for the CKP sensor. The PCM uses the CKP sensor input to calculate engine RPM, fuel timing, fuel quantity and duration of the fuel injection..
Crankshaft Position (CKP) Sensor:
Diesel Particulate Filter
The diesel particulate filter collects the soot and ash particles that are present in the exhaust gas of diesel engines. The diesel particulate filter assembly typically consists of active precious metals deposited on a substrate filter. The exhaust gas is forced to flow through the walls of the porous substrate and exit through the adjoining channels. The particulates that are larger than the pore size of the walls are trapped for regeneration. During regeneration the temperature in the diesel particulate filter increases to greater than 550°C (1,022°F). At this temperature the soot in the diesel particulate filter burns and becomes ash. The precious metal washcoat promotes the regeneration of the trapped particulates through the heat-generating reaction and catalyzes the untreated exhaust gas. The substrate filter is held in the metal shell by a ceramic fiber support system. The support system makes up the size differences that occur due to thermal expansion and maintains a uniform holding force on the substrate filter.
Diesel Particulate Filter:
Diesel Particulate Filter Pressure Sensor
The diesel particulate filter pressure sensor is an input to the PCM and is used to measure the pressure before the diesel particulate filter. The sensor is a differential-type sensor that is referenced to atmospheric pressure. At key ON, engine OFF the diesel particulate filter pressure sensor pressure value reads 0 kPa (0 psi). The range of the sensor is 0-80 kPa (0-11.6 psi).
Diesel Particulate Filter Pressure Sensor:
Engine Coolant 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.
A cooling system concern such as low coolant or coolant loss could cause an overheating condition. As a result, damage to major engine components could occur.
Engine Coolant Temperature (ECT) Sensor:
Engine Oil Temperature (EOT) Sensor
The EDT sensor is a thermistor whose resistance decreases as engine oil temperature increases. The EDT signal is used by the PCM to calculate fuel quantity and injection timing.
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.
Engine Oil Temperature (EOT) Sensor:
Exhaust Gas Recirculation (EGR) Oxidation Catalytic Converter (OC)
The EGR OC helps keep the EGR coolers clean by removing deposits and exhaust condensation, and preventing corrosion in downstream components.
Exhaust Gas Recirculation (EGR) Oxidation Catalytic Converter (OC):
Exhaust Gas Recirculation (EGR) Coolers
The exhaust gasses are directed through 2 EGR coolers to remove heat before the gasses arrive at the EGR valve. Engine coolant is used to reduce the exhaust gas temperature by directing coolant flow through the EGR coolers.
Exhaust Gas Recirculation (EGR) Coolers:
Exhaust Gas Recirculation Temperature (EGRT) Sensor
The EGRT sensor is a thermistor device that monitors the exhaust gas temperature before the EGR coolers. The electrical resistance of a thermistor decreases as the temperature increases, and resistance increases as the temperature decreases. The varying, non-linear resistance affects the voltage drop across the sensor terminals and provides an electrical signal to the PCM that corresponds to measured temperature.
The temperature range of the sensor is between 200°C (392°F) and 900°C (1,652°F) and cannot be accurately measured at room temperature. The nominal output signal voltage range measures 4.6 volts, for temperatures between -40°C (-40°F) and 200°C (392°F) and 0.21 volt at 900°C (1,652°F).
The EGRT sensor is used to determine whether the EGR coolers are operating correctly.
Exhaust Gas Recirculation Temperature (EGRT) Sensor:
Exhaust Gas Recirculation Temperature 2 (EGRT2) Sensor
The EGRT2 sensor is a thermistor device that monitors the exhaust gas temperature after the EGR coolers. The electrical resistance of a thermistor decreases as the temperature increases, and resistance increases as the temperature decreases. The varying, non-linear resistance affects the voltage drop across the sensor terminals and provides an electrical signal to the PCM that corresponds to the measured temperature.
At approximately 25°C (77°F) with the key ON engine OFF, the temperature signal of the sensor is approximately 4.5 volts while connected to the PCM.
The temperature signal range of the sensor is 4.65 volts at -40°C (-40°F) and 0.25 volt at 300°C (572°F).
The EGRT2 sensor is used to determine whether the EGR coolers are operating correctly.
Exhaust Gas Recirculation Temperature 2 (EGRT2) Sensor:
Exhaust Gas Recirculation (EGR) Valve
The EGR valve is a variable position valve that controls the amount of exhaust that enters the intake manifold. The PCM controls the EGR valve which operates between -100 and 100% duty cycles which cannot be viewed by a PID on a scan tool.
The EGR valve operation can be monitored by viewing the EGRVPA PID which displays the actual EGR valve position as a percentage.
Exhaust Gas Recirculation (EGR) Valve:
Exhaust Gas Recirculation (EGR) Valve Position Sensor
The EGR valve position sensor is a potentiometer sensor that monitors the EGR valve movement. The valve position signal is monitored for the desired EGR valve travel position. The sensor is integral to the EGR valve.
Exhaust Gas Recirculation (EGR) Valve Position Sensor:
