Header ????

[HOG4DNR]

I just read O-cha's CEL header fix thread and have a couple questions.

To my knowledge, ALL after market headers do not have a space for the O2 sensor correct and will throw a CEL?

BUT

Do the headers off an E46 M drop right in, do they have the secondary O2 plug in, and without any of the associated CEL problems?

[pokeybritches]

I've had the same questions and confusion regarding the codes from headers, so I'll just summarize what I've gathered from reading:

The secondary O2 sensors' only job in life is to make sure the cats in the headers are functioning properly, and if they are not the sensors throw a code. Many aftermarket headers have secondary O2 sensor bungs installed. However, you can't just plug in your secondary O2 sensors and not get a code, because like I said, their only job in life is to determine if the cats in the headers are functioning properly. Without properly-functioning cats, you get a code. There are three ways around this:

1. Tune - A tune can turn off / turn down the secondary O2s, and no code will be thrown. This is useful for getting rid of the CEL (check engine light). However, your car won't pass an OBDII inspection (where the inspector plugs in a device to your OBDII port). This is a good alternative if you live in an area without emissions inspections. If you do have to deal with inspections, it sucks because it requires two retunes per inspection cycle (one to turn the O2 sensors back on and one to turn them off again).

2. Simulator - There are supposedly two kinds of simulators: electronic and mechanical. I don't know much about electronic. Mechanical simulators limit the amount of air the secondary O2 sensors see. Less air means less pollutants the O2 sensor observes. Simulators can be tricky to design because if the air sample is too limited, the car throws up the bullshit flag and a code ensues. If you don't limit the air enough, the car knows the cats aren't functioning properly. There's a long thread on this on one of the E46 forums, but I don't have the link handy.

3. Relocate the secondary O2 sensors - US spec cars have two sets of cats: one in the headers and one in section 1 of the exhaust. Because the secondary O2 sensors only determine if there is a cat in place, one could relocate them to after the cats in section 1 of the exhaust. I've read of one person doing this successfully on a Z4M, and never heard of anyone having issues doing it on the Z4M.

You could just live with the light. The secondary O2 sensors don't play any role in the closed loop operation of the engine. They just tattle on you when you install your headers. However, I will say this:

In any emergency in an aircraft, the pilot should quickly get rid of the flashing Master Caution light (usually by simply pushing it) because it alerts him of new warnings and cautions. If it is already flashing it's more difficult to recognize when new warnings or cautions appear. I would treat my check engine light the same way. If it is already on it is more difficult to determine if your engine is malfunctioning.

[boydgti]

Good info thaxs

[Diokaef]

Originally Posted by pokeybritches

I've had the same questions and confusion regarding the codes from headers, so I'll just summarize what I've gathered from reading:

The secondary O2 sensors' only job in life is to make sure the cats in the headers are functioning properly, and if they are not the sensors throw a code. Many aftermarket headers have secondary O2 sensor bungs installed. However, you can't just plug in your secondary O2 sensors and not get a code, because like I said, their only job in life is to determine if the cats in the headers are functioning properly. Without properly-functioning cats, you get a code. There are three ways around this:

1. Tune - A tune can turn off / turn down the secondary O2s, and no code will be thrown. This is useful for getting rid of the CEL (check engine light). However, your car won't pass an OBDII inspection (where the inspector plugs in a device to your OBDII port). This is a good alternative if you live in an area without emissions inspections. If you do have to deal with inspections, it sucks because it requires two retunes per inspection cycle (one to turn the O2 sensors back on and one to turn them off again).

2. Simulator - There are supposedly two kinds of simulators: electronic and mechanical. I don't know much about electronic. Mechanical simulators limit the amount of air the secondary O2 sensors see. Less air means less pollutants the O2 sensor observes. Simulators can be tricky to design because if the air sample is too limited, the car throws up the bullshit flag and a code ensues. If you don't limit the air enough, the car knows the cats aren't functioning properly. There's a long thread on this on one of the E46 forums, but I don't have the link handy.

3. Relocate the secondary O2 sensors - US spec cars have two sets of cats: one in the headers and one in section 1 of the exhaust. Because the secondary O2 sensors only determine if there is a cat in place, one could relocate them to after the cats in section 1 of the exhaust. I've read of one person doing this successfully on a Z4M, and never heard of anyone having issues doing it on the Z4M.

You could just live with the light. The secondary O2 sensors don't play any role in the closed loop operation of the engine. They just tattle on you when you install your headers. However, I will say this:

In any emergency in an aircraft, the pilot should quickly get rid of the flashing Master Caution light (usually by simply pushing it) because it alerts him of new warnings and cautions. If it is already flashing it's more difficult to recognize when new warnings or cautions appear. I would treat my check engine light the same way. If it is already on it is more difficult to determine if your engine is malfunctioning.

Nice.

[O-cha]

Your best bet is to get a tune to get rid of the CEL, I'm not going to be selling the simulator because of variances between cars make it very hard to dial in remotely.

[HOG4DNR]

Thanks for the info, very informative.