I did a lot of searching and I am not looking for a debate on Cat removal.... I just want to know if I put in a pipe in its place will my SES light come on? If so how do I fix it?

i gutted my cat and the ses light came on once. I hooked it up to a code scanner, the code was for the egr system. but i haven't seen it since.

So it was unrelated? Anyone else have input?

Apparently the factory style EGR needs a little backpressure to work properly. Buying an aftermarket type that doesn't need that backpressure solves the problem.

Did you do this yourself? What do you recomend?

yea, I was going to take off my at the other night and bolt on a straight pipe in place, but what do you do with the line coming into the sde of the cat. I think it goes to the egr or something on the air pump. Im in GA and need to be able to bolt back up the cat for emissions next year. Thats why I cant just weld on or gut the cat.

I don't have an LO3, and that seems to be the engine that is the most susceptible to it.

It has been reported on other forums such as TBI and Engine Swap.

I have used the aftermarket style EGR on a different application (Buick 3.8 in a California '81 Malibu). It worked fine.

IIRC, the factory uses a "positive" pressure EGR valve, and the replacement will be a "negative" pressure valve.

So EGR and Smog both use the line to the Cat?

Honestly crrllmich, I can't remember which one it was. I read in my Haynes book last night that it was one or the other, but don't remember which. I do remember that flow from the line is controlled by a diverter valve either going to the cat or if it gets to hot, goes somewhere else, just can't remember where. I just need to know what to do with the line if I install a straight pipe where the cat is and if I'll throw any codes.

EGR uses passages built into the heads and intake manifold.

The tube to the cat is for the Air Injection Reaction system, comes off of the diverter valve that is connected to the output of the A.I.R. pump, aka "smog pump".

Can I disconnect it at the cat and leave it?

If thats for the Smog and not EGR then why would the SES light come on if I remove the cat under EGR? Im cunfused.

The tube has nothing to do with EGR. I never said anything about removing the tube causing the SES light.

Removing the cat reduces the backpressure to the engine, which reduces the pressure on the exhaust side of the EGR valve, which reduces its ability to open up, which sets the SES light.

Thanks! just the info I was looking for! Could you explain the aftermarket EGR a little more. Maybe some links to products. THANKS! You have been a great help

Go to www.partsamerica.com . Near the top is "My vehicle" - enter your vehicle info. Click on Replacement Parts, Emissions, EGR valve (or search for EGR valve). Niehoff FE3171 will come up, for instance (pic below). Note the "POS" stamped on the edge of the vacuum diaphragm housing - that means "positive", it's not an acronymn.

So pop that on and no more ses light?


pos lol

It's worth a try. Many success reports from TBI guys with high flow, low restriction exhaust systems.

Took the cat off today SES light didnt come on. So do not know what to tell you. I will let you know if it comes on. I will be replacing the muffler this weekend.