If my check engine light is on and keeps reading "O2 sensor circiut malfuction" even after changing the sensor could it be the lack of EGR(exhaust gas recirculation) which is a "common problem" w/ this car. Could it be something in the wiring of the sensor?
EGR or O2 sensor on 1999 Mercury Cougar
by mdinight rider in Boonsboro, MD on March 31, 2009
ANSWER by irvtech , April 01, 2009
Usually if you have lack of EGR flow, you get EGR flow dtc's(diagnostic trouble codes) O2 sensor circuit malfunction could mean wiring to the sensor or the sensor heater are bad. If the sensor heating circuit does not draaw the correct amount of current the Oxygen (O2) sensor heater maybe bad the sensor needs replacing, given fuses and all wiring are intact.You could have this problem using an aftermarket sensor. Most times O2 sensor codes are a reflection of possible vacuum leaks, low fuel pressure conditions or other engine running concerns, Too many times untrained people read out codes and there are O2 Sensors codes, they change the O2 sensor and have the check engine light come on again. You need to have the correct cause diagnosed, so I recommend finding a reputable shop to do the diagnosis. Most times doing this will save you from changing parts unnecessarily. Good luck.
ANSWER by OPTIMUSKISS , October 05, 2009
WELL IM NO MECHANIC..BUT I WAS TOLD THAT HAVING YOUR CATALINIC CONVERTS PUNCHED OUT WILL CAUSE THE ECM(COMPUTER) TO READ THAT YOUR O2 SENSOR IS BAD..NOT TOO SURE ABOUT THIS..BUT YOU COULD CHECK IT OUT.