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Discussion Starter · #1 ·
ok, so I have a check engine light. I scanned it and its for a rear bank 2 oxygen sensor. I took a rag and held it in front of both tailpipes to see if it may be a bad cat causing the o2 sensor to misread. the passenger side tailpipe seemed to move the rag just a little less (a very small amount, I am not completely sure if I am even making it up) and there seems to be a misfire at idle on that side, which I noticed happening maybe three times as much as on the drivers side. if it was a bad cat, would it not move the rag at all, or would it be a hardly noticable difference to the drivers side?

thanks,
steve
 

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What is the code for? There's a lot of codes for a rear 02 sensor. Circuit malfunction, not switching, catalyst efficiency below threshold, etc. The only one that would single out the cat would be the catalyst efficiency code. A broken up cat that is restricting the exhaust would cause there to be less flow out of the one side. This could be easier for you to diagnose since you have true dual exhaust.
 

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The only reason that code will come up is a bad/corroded connection to the 02 sensor, damaged wiring, a damaged sensor, or a faulty PCM. Check all the wiring to the sensor and disconnect the plug and look at the contacts to make sure the wiring is all good and the pins aren't corroded. If all checks out, then it looks like the sensor is probably bad. But this doesn't explain the difference in flow between the two sides. What you should do is bang up on the catalytic converter. If you hear and kind of jingling around inside, then the catalyst has broken up and needs to be replaced.

And just in case you might not know, this is the rear sensor on the driver's side.
 

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Resident drifter
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Discussion Starter · #5 ·
thanks, I appreciate it. I may just be imagining the difference in flow, im not sure, but I'll check it out, thanks. I am actually in school for this now, but I had classes involving this stuff like a year ago, and I just wanted to double, and triple check myself, because I dont want to start throwing parts at it and wasting money.

thanks again,
steve
 

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remove the forward 02s and then start it up and see if it idles/runs diff...so you have true duals with no crossover?
 

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Don't worry about the rag moving. Unless your exhaust system is perfectly symetric in terms of flow restriction, one side will flow more than the other because of the length of pipe, number of bends, quality of welds, etc. The least restrictive side will flow more.

Pete
 

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remove the forward 02s and then start it up and see if it idles/runs diff...so you have true duals with no crossover?
That is horrible advice. Removing the front oxygen sensors will prove nothing as first of all they aren't used during start up and however long it takes to reach closed loop operation and second, the car will never reach closed loop operation and will run off of tables.
 

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That is horrible advice. Removing the front oxygen sensors will prove nothing as first of all they aren't used during start up and however long it takes to reach closed loop operation and second, the car will never reach closed loop operation and will run off of tables.
REmoving the front O2s will let you know if you have a plugged cat. Its not horrible advice Ive worked in shops and seen 20+ year experience mechanics do this. Also some car repair manuals recomend this procedure to check for a pluged cat. I have also seen pluged cats the car comes in an the suckers just glowing lol. if you remove the 02s it will alow the exhaust that was backing up into the port escape. Also there is nothing wrong about running without 02s I once drove 50 miles with the 02s unplugged car ran fine the computer will just stay in open loop.
 
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