Will aftermarket headers and a cat back exhaust throw a CEL?
 

I have a 1999 2.5 box and want aftermarket headers and muffler. Will it cause CEL?
If it will, what can be done to correct it?

If you keep the cats and the o2 sensors you should have no trouble with CEL.s

Check out Turbowerx headers I have not had a problem from anything he makes.

You have the manifold, then an oxygen sensor, then the cat, then a second sensor, and then the muffler. You need that first sensor for the car to run properly. The second sensor is there for the EPA and has nothing to do with performance. The second sensor talks to the first sensor to determine if the cat is working. ROW cars do not have the second sensor.

If you do not have the second sensor hooked up then you get a check engine light because the DME thinks the cat is bad. But this is the funny part. You can have the second sensor hooked up to the electrical connector, but the sensor not screwed into the exhaust stream. You get fault codes but no check engine light. I ran my car this way for a while, in the interest of Boxstir science of course.

What I am about ready to do is to reprogram my 2.5 DME as a ROW car. Then the DME will not be looking for a second sensor after the cat. In the interest of science of course....

Tool Pants, I've been meaning to research this same project. Do you know if you can also reprogram the DME for a 2000 Boxster S to the ROW program and eliminate the second O2 sensor? Do you anticipate any problems with California smog? I had mentioned this to Loren and he said he could do the reprogram with his PST2. I might have to get this done at the June 7th Work On Cars Day in Sacramento just as an experiment like you're doing. I imagine you can do this and just leave the cats and second O2 sensor in place with no problems.

Loren knows how to do this, but you have to get the DME programming code otherwise you cannot switch. And guess who has that code and the other codes for your car??

I have mine, so I am one key stroke away from a ROW DME. Your screen will look different since my 1997 DME is an older version, Mine is a V as that is the letter for 1997. W is 1998-1999. The DME changed in 2000. I think your 2000 shows up as LEV for low emission vehicle.

I don't think a smog machine is sophisticate enough to detect a programming change. I am very rusty on this so don't quote me, plus there is new smog equipment. In the old days I think the machine checked the DME to see how many readiness codes were set, if there were any fault codes in the DME, and I seem to remember it could check to see if the VIN in the DME matched the VIN of vehicle being tested.

The only issue I anticipate is the number of readiness codes the machine sees. On my 2.5 there are 5, 1 of them being catalytic converter efficiency. I guess with a ROW program this readiness code goes away since the second oxygen sensor is required to test the cat efficiency, and there is no second sensor on a ROW car. But since my 2.5 only need 3 of the 5 codes set for smog it may be a moot point.

My 6th smog inspection is due in March. Stay tuned....

Is there any performance benefit to running the RoW-spec program compared to the U.S. spec program?

So I need to get the DME programming code for my specific car? I assume I have to go to the dealer for this and that Loren can't just get it out of my DME, correct? What did you have to do to get your programming code?

Since you're in Cali too I might just wait and see how this change goes for you and how you do in smog. My car is 100% stock now for emissions, so I don't really have a pressing issue. I'm just thinking ahead to this fall and maybe doing some exhaust work then - cat-less headers and by-pass valves on the mid-pipes. Please keep us in the loop on how your DME changes go.

I'm very interested in doing this myself. Todd, when are we meeting for a beer ;)

Patrick