Mitsubishi Eclipse II technical information manual page 60

text version of content this owner's manual page from owners manual to the vehicle Mitsubishi Eclipse, year of production 1995 - 1999:

ENGINE - Control System 02 Heater Monitor LBackground flow to decrease. The02 sensor’s heater maintains In order for the02 sensor to function properly, the the temperature of the sensor to around 1200°F. 02 sensor must be heated to approximately 572“ - 662°F. To assist the 02 sensor in achieving thisAfter the engine has started, the upstream02 sen- temperature, the O2 sensor is equipped with a Posi- sor’s information is used by the PCM to assist in tive Thermal Coefficient (PTC) heater element. Boththe air/fuel calculation. If the sensor is not up to the upstream an downstream’s heater element is fed battery voltage any time the MFI relay is ener-operating temperatures, the information given by the sensor may be inaccurate, possibly causing gized. The ground for the heater element is routed through the 02 sensor’s 4-pin connector to an exter- an increase in emissions. The downstreamO2 sensor is used by the PCM nal ground source. As current flows through the element, the temperature of theO2 sensor in- to calculate the efficiency of the catalytic converter. The sensor must be heated to allow the02 sensor creases. As the temperature increases, the resis- to function normally. Without the O2 functioning nor- tance of the element increases causing the current mally, the catalytic converter test would be invalid. Operation sor that has cooled enough by detecting an increase The resistance of the02 sensor changes with tem- of 0.49 - 1.56 volts higher what the PCM detected perature and age. It’s resistance normally is between at the beginning of the test. The maximum amount 100 Sz to 4.5 MegR. When the temperature of the of time to perform this portion of the test is 144 sensor is increased, the resistance of the sensor decreases. Inversely, as the sensor ages, the resis-seconds. tance increases. It is the resistance of the sensor’s When the O2 sensor has cooled enough, the PCM output circuit that is tested for proper heater opera- tion, not the heater element itself. energizes the MFI relay for the next 48 seconds. With the relay energized, current should flow through the heater element causing an increase of tempera- LThe test begins approximately 5 seconds after the engine has been turned off with the ignition keyture at the sensor. As the heater warms the 02 sensor, resistance of the02 sensors output circuit and battery voltage greater than 10 volts (the PCM should decrease. As the resistance decreases, volt- still operates even though the key is in the off posi- tion). Once the timer has timed out, the PCM biasage at the PCM decreases. While the MFI relay is energized, the PCM pulses the 5 volt biased signal 5 volts to the O2 sensors output wire once every 30 times. Each time the biased voltage is activated, 1.6 seconds, and keeps it biased each time for the PCM checks for a voltage drop. The02 heater 35 ms. During this portion of the test, the PCM monitor test passes if the PCM detects at least monitors the voltage on the output wire of the 02 0.157 volt decrease in 15 out of the 30 pulsed sig- sensor. As the sensor cools down, the resistance nals. should increase, causing the PCM to register an increase of voltage. The PCM determines a 02 sen-

owners manual Mitsubishi Eclipse

owners manual Mitsubishi Eclipse - year of production: 1995, 1996, 1997, 1998, 1999 - Mitsubishi Eclipse II technical information manual EN