Celica Forums General Discussion Exterior CEL after install of exhaust

Question, I had a custom exhaust run from the header back, removing the cat and had a better res. put in. It was fine for 2 days and then the CEL came on, I reset the ECU and it was fine for another day or 2 and then came on again. Is there anything that I can do, short of removing the light bulb? I had them put the 2 02 sensors in the same place but the cat was removed so it's probably getting a real rich reading. It's really not a problem but was wondering if some had a solution. thanks in ADV.

The removal of the Cat is your problem, those two sensors work together ... one is suppose to take the reading before the cat, the other after.

By removing the Cat, it is throwing off the ECU and you will always get a CEL now. I believe the ECU is now always confused to it goes to a pre-program a/f curve to protect the engine, it's not going to make any adjustments, so by removing the car I don't believe you are getting the gain that you hoped for.

Would that hurt perf.???? Cutting the cat off and all?? Seems like it would lose back pressure.

no back pressure is great for high reving ... you will loose power on the low and midrange.

ok, so just ignore the light?

I have actually notice a big improvement in the hole shot

Wow...I always thought it was a bad idea to cut that off!! I was wrong I guess. So, if I had a larger pipe ran from the headers, cut the cat off and ran no muffler or a glass pack; It would be better than what I have now?? (No res. and glass pack)

I don't know about any kind of gains but I know that the ECU goes into a protect mode when those two sensors are NOT working correctly.

It says so right in the Toyota Maintenance Manual. I don't remember 100% but I doubt it's very good for the engine. I'd have to read it again.

KEEP the res. I took it off at first and you could hear it for miles!!! but I have a 2.5in pipe and it make a big dif.!!!!!

is custom piping better do you feel a lot of difference

I never had a name brand aftermarket exhaust, but over the stock exhaust there is a huge difference in the lower end.

removing the cat is a big improvment in performance for the celica gts! but unfortunatly the ecu clamps down on the gains after a few days.the only way it can be done without the ecu messing things up is to get one of those devices that immitates the second o2 sensor(showing a normal reading of o2 to the computer).

i've heard of these, but where can you find one for the celi?

you can search the forums for the info on how to make one or you can contact splitsecond.com this is a partial clip message from splitsecond.
"We have the ESC2 which connects to the rear O2 sensor(s). It keeps the
>check engine light from coming on when you take off the cat.

>Regards,

>Mark "
hope you get it soughted out,its an awsome feeling with you cat out,right!