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CEL is on because of malfunctioning O2 sensor

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98FWDSM

15+ Year Contributor
180
0
Jul 27, 2003
O2 sensor heater circuit malfunction (bank 1 sensor 1) code #P0135 and #P0420 catalyst efficiency below threshold (bank 1)... this is why my check engine light keeps coming on just about every day. the P0420 code has been coming on ever since i had the cat beaten out. but the P0135 is a new one. is it possible that i have been running so rich that i melted the O2 sensor? or is it possible that i need to replace mine? also, i dont know if it is just me imagining it but i feel like i have a slight loss of power.

thanks :dsm:
 
Chances are your O2 sensor (the one at the exhaust manifold) is malfuctioning. The only sure way to tell is to monitor its activity through a datalogger. How many miles do you have on the O2 sensor? What makes you say you are running rich? Prolonged rich mixtures will foul an O2 sensor.
 
Just take out the second 02 sensor and rap it in tip foil. ziptie it somewhere inder your car and block off the hole for it. Thaty will work
 
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