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Decatting a grand prix. Rear O2 sensors....



supposedly 01+ cars use the rear o2 sensor for fueling somehow. when it sees no rear o2 sensor readings it goes into some form of 'dump more fuel in' mode. it's really hit or miss to whether people have actually experienced it or not.
 
01+ goes into a CAT diagnostic when the rear 02 is deleted by code. It will sometimes cause the LTFT's to fluctuate back and forth and may cause the car to surge, it is testing the CAT. The only way to disable this is to run an 02 emulator or install the rear 02 so it is not directly in the exhaust stream or disable this diagnostic using a program called tiny tuner.

It doesn't run this test at all times, just when it feels the need to run this test, then goes back to normal.
 
FoSHO99 said:
01+ goes into a CAT diagnostic when the rear 02 is deleted by code. It will sometimes cause the LTFT's to fluctuate back and forth and may cause the car to surge, it is testing the CAT. The only way to disable this is to run an 02 emulator or install the rear 02 so it is not directly in the exhaust stream or disable this diagnostic using a program called tiny tuner.

It doesn't run this test at all times, just when it feels the need to run this test, then goes back to normal.
Click to expand...

That explains my surge issues,thank you so much. Will have the tune modified,seriously I thank you.
 


Bob Padilla said:
That explains my surge issues,thank you so much. Will have the tune modified,seriously I thank you.
Click to expand...

How often and how much did your car surge though? I ask that because most times this test is ran, not too many people notice or realize their ltfts are fluctuating, unless you are scanning or keeping a constant eye on it.
 
FoSHO99 said:
How often and how much did your car surge though? I ask that because most times this test is ran, not too many people notice or realize their ltfts are fluctuating, unless you are scanning or keeping a constant eye on it.
Click to expand...

It'll surge like I put the cam in already lol and at times die out. My exhaust is'nt stock by any means so when it surges I could tell lol. So could my neighbor.:)

I'm going to try and get it retuned this next week,i wonder if that test is messing with my front 02 since when it does it I get the great 1133 code. Hmm?
 


1133 is like when the pcm read a slow transfer from closed loop to open loop or somthing, im lazy and didnt google it.

I get the same code with my headers, and the fact that my extension harness is burned.
 
Not really anything else to add, there are a lot of things that may cause a car to surge, disabling this test using tiny tuner may help some, not at all or help a lot... lol

Front 02 codes are common with homemade extensions. I say if you're going to run headers, get a bung or 2 welded in the crossover near the rear head. Then you don't need an extension, won't worry about water, don't have to worry about it hitting the firewall and it's easy to replace, as well as having an extra bung for a wideband if needed. The other problem at times is the tune, tune with a wideband and make sure your fuel is close to commanded afr. If you own a tuner and wideband, try running open loop getting a couple tunes for different times of the year and ditch the front 02.

Usually if the front 02 is really dead, it will stay at 435v or so, just steady.
 
FoSHO99 said:
Not really anything else to add, there are a lot of things that may cause a car to surge, disabling this test using tiny tuner may help some, not at all or help a lot... lol

Front 02 codes are common with homemade extensions. I say if you're going to run headers, get a bung or 2 welded in the crossover near the rear head. Then you don't need an extension, won't worry about water, don't have to worry about it hitting the firewall and it's easy to replace, as well as having an extra bung for a wideband if needed. The other problem at times is the tune, tune with a wideband and make sure your fuel is close to commanded afr. If you own a tuner and wideband, try running open loop getting a couple tunes for different times of the year and ditch the front 02.

Usually if the front 02 is really dead, it will stay at 435v or so, just steady.
Click to expand...

Thanks for adding that sir it is welcomed and well appreciated.:)
 
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