OBD2+header=No codes

[cory2081]

Don't know how many people have the problem of the check engine light coming on after installing a header on a 96+ 240. I just installed my Nismo header, instead of putting the 2nd O2 back in the exhaust stream, I just mounted it on the bracket that holds the O2 connector to the transmission. I'm not getting a check engine light at all. Thought this might help someone out there. It's probably fooling the O2 sensor b/c there is more oxygen outside than in that exhaust stream. All it is looking for is a different voltage than the primary O2. Just my $.02

[yozsi]

well how long have you been driving it?

[cory2081]

several days now. if it's going to come on, i'm pretty sure it would have already. i'll keep everyone posted, if it does come on, i have a schematic for an MIL eliminator.

[NISTECH]

your statement about the sensor looking for a different voltage is incorrect. the rear sensor does a comparison between the 2 and looks to see if the 2 are reading with in 75%(approx) of each other if the 2 begin to sweep within that range together there will be a check engine light for cat code po 420. I dont suspect you will see that code the way you have that rigged up. but you may see a code between po130 and po 160 indicating a bad rear o2 rather then cat. since its voltage will most likely be locked at or near 0 volts all the time. I am quite perplexed that you have not seen a check engine light after a couple days of driving. does your check engine light even work? should come on when turning the key to the on position then shut off after starting. if in fact it is working I would really like to see what the sensor is registering with a DSO while driving it. that would be interesting!!

[cory2081]

I said "different voltage" not the same. I know how these systems work. Yes, my MIL works...that's Malfunction Indicator Lamp in case you didn't know...haha, j/k. That's what GM calls it anyway. Still no code!!! I may have to grab a tech2 and see what the O2 is reading. Oh...and that thing about the MIL coming on when the key is in the "on" position without the engine running, I knew that too. That is just a way of checking the ECU's diagnostics, it sets a code for no engine RPM, code 12 on a GM OBD1. Can't remember the OBD2 code off hand.

[NISTECH]

yea thats what i said. I thought you were working on a nissan not a GM.

[cory2081]

ummm, yeah it is a Nissan......but it's OBD2 and you should know that all these systems are the freakin same. An O2 sensor is an O2 sensor, they all work the same way as do all of the other sensors. They may be different brands that work on different reference voltages, but, they still work the same. My point is that if the rear O2 is reading the same voltage as the primary one, it will set a code. I was just telling people about my way of preventing the MIL from coming on, it works on my car, just thought it might help some other member out. I was just letting you know that I know how these systems work. I may not know the specifics for Nissans, but, I know enough. Hell, I've only had the car for a few months. Well, gotta go install these Tanabe rear camber arms!! Someone with a header try my method and see if it works on your car

[yozsi]

the reason it has not come on is because it thinks the cat convertor is working so well that no emmisions are coming out of the tail pipe.

[NISTECH]

cory when you get a chance to hook up a DSO to that sensor and drive it. post what you find the readings do. I am very curious as to how it reacts.

[cory2081]

Yeah, I am curious too. I have heard others on here say that thier car didn't throw a code after installing a header. Who knows.....and my second cat isn't a dummy like most peoples. So, I still have 1 cat to get rid of....although, the car is loud enough, so, I think that last cat can stay...lol.

[s14a]

where u get a nismo header?

[cory2081]

I bought it used for a real good price It's the exact same as a Hot Shot....in fact, Hot Shot makes it for Nismo, or so I have read.

[cory2081]

Well, my check engine light came on tonight. Might be b/c of the cold weather. I'm 99.9% sure that it's the code for the 2nd O2. Oh well, it worked for over a month!! lol Maybe I'll try this simulator circuit when I get time.