Catalytic Converter
The catalytic converter plays a major role in the emission control system. The catalytic converter operates as a gas reactor. Its catalytic function is to speed the heat-producing chemical reaction of components in the exhaust gases in order to reduce air pollutants. The catalyst material inside the catalytic converter consists of a ceramic substrate.
The catalytic converter is designed to provide a long life. No maintenance is necessary for the catalytic converter.
Exhaust Gas Recirculation (EGR) Actuator and Valve Position Sensor
The EGR actuator is a variable position valve that controls the amount of exhaust that enters the intake manifold. The EGR actuator is controlled by the PCM using a pulse width modulated (PWM) signal that varies from 0-100%. The EGR actuator consists of 2 components, a valve with an actuator, and a position sensor to monitor valve movement. The EGR valve position sensor is a potentiometer sensor which is needed to give the control circuit feedback to achieve the desired travel position. When the EGR receives a 5 volt reference signal and a ground from the PCM, a linear analog voltage signal from the sensor indicates the position of the EGR valve. Input signals from the manifold absolute pressure (MAP), exhaust pressure (EP), and barometric pressure (BARO) sensors are used by the PCM to calculate and control the EGR system flow.
Scheme 16
Exhaust Gas Recirculation (EGR) System Cooler
The exhaust gasses are directed through the EGR system cooler 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 system cooler.
Scheme 17
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 VGT and EGR valve control.
An open or short in the EP sensor wiring results in an out-of-range low voltage at the PCM.
Scheme 18
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.
Scheme 19
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.
Scheme 20
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.
Scheme 21
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.
Scheme 22
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.
Scheme 23
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.
Scheme 24
Exhaust Gas Temperature (EGT) Sensor
The EGT sensor is a resistance temperature detector (RTD) type sensor. The EGT sensor is an input to the PCM and measures the temperature of the exhaust gas passing through the exhaust system. The electrical resistance of the sensor increases as the temperature increases, and resistance decreases as the temperature decreases. The varying resistance changes the voltage drop across the sensor terminals and provides electrical signals to the PCM corresponding to temperature.
The PCM uses the input from 3 EGT sensors to monitor the exhaust gas temperature. The first sensor is located before the OC. The second sensor is located between the OC and diesel particulate filter. The third sensor is located after the diesel particulate filter.
Scheme 25
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 sensor voltage input to the PCM increases as the pressure increases. The EP sensor, located at the left rear of the engine, measures the pressure in the exhaust manifold. The sensor feedback signal is used for variable turbocharger geometry and EGR valve control.
An open or short in the EP sensor wiring results in an out-of-range high or low voltage, at the PCM.
The output of the sensor ranges from 0.175 volt 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.