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Old 12-13-2015, 11:59 AM   #2589
FTemplar
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Quote:
Originally Posted by steve99 View Post
The catback is so far away from the 02 sensors that monitor the primary cat in the header it would be virtually impossible for it to have any effect on the reading of those sensors.

you either have an exhaust leak, stuffed o2 sensor or your primary CAT is actually stuffed, if you track cars or drive them hard enough its possible to overheat and disintegrate the primary cat in header. It the only one monitored by ECU.

It also possible that your intake (assume its untuned as you would have disable CEL in tune) is throwing of the fueling enough to be causing the cat efficiency cel as well.

The ECU derives that cel from comparing the reading from the primary and secondary o2 sensors either side of the primary cat in the header, abnormal reading caused by missing or damaged cat, fueling way off exhaust leaks etc will cause it.

never heard of anyone getting that cel from a catback.
I'm not versed as well as you are in mecanics, all I know is that my car is stock except for my catback and air filter, but if you're right then i'm gonna have to have my header's cat checked out then. Not that it's a huge annoyance right now but still.
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