EGR Temperature Sensor: Description and Operation
PURPOSEFig. 39 Egr Valve Location, 16V (California):
The EGR system is designed to reduce NOx emissions.
The three major components used in the EGR system are the:
EGR valve
Vacuum amplifier
Vacuum thermo-switch
The EGR valve is located on the back of the intake manifold. The function of the EGR valve is to control the amount of exhaust gas returned to the combustion chamber to reduce the peak combustion temperature.
By reducing the peak combustion temperature, the formation of oxides of nitrogen (NOx) is reduced.
EGR VALVE OPERATION
Fig. 37 Vacuum Amplifier, 16V (California):
The EGR valve is opened by intake manifold vacuum via the vacuum amplifier. The purpose of the vacuum amplifier is to supply vacuum to the EGR valve during acceleration (low manifold vacuum).
Fig. 35 Vacuum Hose Diagram, 16V (California):
The vacuum amplifier receives two vacuum inputs. The primary input is directly from the intake manifold and the secondary input is from the throttle body (ported vacuum) before the throttle plates. The primary vacuum input is used to operate the EGR valve, while the secondary input is used as a control reference. For examine, when the vacuum inputs are equal, such as during wide open throttle, the EGR valve will close, allowing peak engine performance. The EGR valve should be open only during part throttle operation.
THERMO-VACUUM VALVE
Fig. 38 Vacuum Thermo-switch, 16V (California):
A thermo-Vacuum valve, is installed in the primary vacuum supply line to the vacuum amplifier. This valve will open and allow the EGR valve to operate when the coolant temperature reaches approximately 50°C (122°F). The valve will close when the coolant temperature is below approximately 27°C (81°F).
TEMPERATURE SENSOR
Fig. 39 Egr Valve Location, 16V (California):
An EGR temperature sensor is located in the intake manifold near the EGR valve. It is used to inform the CIS-E Motronic control unit if the EGR system is functioning properly.
The sensor is used to measure the temperature of the recirculated exhaust gas coming from the valve. This sensor is a malfunction detection sensor only.
If the EGR valve, temperature sensor or wiring fails, the fault is stored in the CIS-E Motronic's permanent fault memory, and also illuminates the "CHECK" light which is located to the right of the instrument panel.
All emissions related faults will be stored in the CIS-E Motronic's fault memory, and on California vehicles, the engine "CHECK" light to the right of the instrument panel will illuminate if a fault exists.