straight pipe added and a code

[RdyPlr1]

So I removed the mufflers and had a shop fab up some straight pipes. I installed some dei heat tape. Drove around for about two days and got a cel.. checked code:

P006800 manifold pressure/throttle position correlation.

I was driving and punched the gas and car went into limp mode ... CEl, traction light and another light came one. Is it possible I didn't tighten the pipes from manifold to the first cat? Any thoughts?

Edit: Adding the straight pipe was NOT the cause of the cel.

[01sapphirebob]

Do you have the ARROW controller for your car? If not, thats probably why.

[RdyPlr1]

Why would I need a tune for a muffler change?

[texasram]

You need a tune for almost anything on the gen v

[ViperGeorge]

Do you have headers? What did you do with the down stream O2 sensor? Is it possible you melted the O2 wire? This will cause limp mode and other assorted problems. Check your ASD fuses.

[RdyPlr1]

I removed the entire exhaust so the shop could measure up the pipes.. no headers.. the o2's went right back in their place when I put the exhaust back in. Nothing got moded but The pipes. What is the asd fuse? Obviously located on the fuse box, is it numbered ?

[nx91notch]

The sensor that measures that isn't remotely close to the exhaust. It's on the passenger side of the intake manifold. As to why this code showed up now I don't have an answer.

*edit: I just looked at the diag flow chart for this code and one of the possible causes is restriction in the exhaust. One of the steps was to check for exhaust leaks and/or a restriction. Obviously with the mufflers gone I doubt there is restriction. Check for leaks and go from there.

[RdyPlr1]

The sensor that measures that isn't remotely close to the exhaust. It's on the passenger side of the intake manifold. As to why this code showed up now I don't have an answer.

*edit: I just looked at the diag flow chart for this code and one of the possible causes is restriction in the exhaust. One of the steps was to check for exhaust leaks and/or a restriction. Obviously with the mufflers gone I doubt there is restriction. Check for leaks and go from there.

Thanks for checking... Yea, can't imagine there's restriction, but maybe I didn't tighten down the one or both of the clamps enough. Maybe why the code is "manifold pressure" , it's leaking out.

Here's some pics of what I did:

[SRT BILL]

I'm no engineer but that straight pipe looks small in diameter. Any cat back would have some type of chamber for the exhaust to fill before exiting out the end. Your restriction could be the straight pipe. Just say in.

[nx91notch]

I'm no engineer but that straight pipe looks small in diameter. Any cat back would have some type of chamber for the exhaust to fill before exiting out the end. Your restriction could be the straight pipe. Just say in.

After seeing his pics I think I agree with this.

[Dave1968]

I was thinking the same thing. What about using 3" or so, would that mimic the expansion of the muffler enough? Is all this going to help much - I thought the mufflers were just straight through, they can't be very restrictive - is there a big weight savings getting rid of them?

[RdyPlr1]

Ugh... iT sounded nice too. There goes four hours of wastes time. I'm may step up and buy a system.. I'm not going back into those sills to return to stock.

[RdyPlr1]

I was thinking the same thing. What about using 3" or so, would that mimic the expansion of the muffler enough? Is all this going to help much - I thought the mufflers were just straight through, they can't be very restrictive - is there a big weight savings getting rid of them?

The stock muffler are straight through yes, however they have holes inside the piping and I think that's what Bill is referring to when he said "the exhaust to fill". The weight savings is small, certainly not worth the time to remove sills... Which I have to do again apparently

[Sub Driver]

You need a tune for almost anything on the gen v

Incorrect. Not needed for a simple catback change.

[sadil]

I still think you might have a leak, over the code setting for a lack of restriction on the pipe. What kind of gaskets did you use between tbe cars and headers?

[CHAP]

Ugh... iT sounded nice too. There goes four hours of wastes time. I'm may step up and buy a system.. I'm not going back into those sills to return to stock.

Do you have cabine drone with the straight pipe ?

[ViperGeorge]

I removed the entire exhaust so the shop could measure up the pipes.. no headers.. the o2's went right back in their place when I put the exhaust back in. Nothing got moded but The pipes. What is the asd fuse? Obviously located on the fuse box, is it numbered ?

I don't remember the fuse numbers but they are located in the Power Distribution Center in the engine compartment. There are two. The O2 wires, if they touch or are too near the exhaust pipe, can melt. When this happens it is common for the ASD fuse or fuses to blow. If they blow the car will barely run and will have no power. You will also get various warning lights and a CEL. One to many codes will show up as well.

However, after looking at the pictures you posted I would agree with the others, the pipes look awfully small in diameter. What size pipe did you use? Even so, do be careful about how the O2 wires are run to minimize their exposure to exhaust heat.

[Steve M]

As long as that pipe is 2.5" in diameter, it isn't a restriction.

There are a few sanity checks performed by the PCM on the intake side of things. Airflow is measured by the MAF sensors (one in each intake tube), and there's also a MAP sensor in the manifold. It looks at the MAF readings, compares that to the reported throttle blade angles, and looks at the air pressure reported by the MAP sensor...I'm not sure what the threshold is, but if the airflow before the throttle bodies doesn't jive with the pressure being reported in the intake manifold, it'll set this code and throw the car into limp mode.

My advice is to go over everything on the intake side of things...make sure there are no loose connections (MAF sensors, throttle bodies, or MAP sensor), and make sure there are no vacuum leak sources (loose clamps, loose MAP sensor, loose throttle bodies, or loose vacuum lines from the PCV or brake booster). If the problem persists, then try swapping back to the stock exhaust (or something like it)...I don't think that'd be the problem here, but these PCMs are borderline retarded when it comes to not liking mods.

[RdyPlr1]

I still think you might have a leak, over the code setting for a lack of restriction on the pipe. What kind of gaskets did you use between tbe cars and headers?

No gaskets used.

Do you have cabine drone with the straight pipe ?

Yes, a bit more then stock.

[RdyPlr1]

I don't remember the fuse numbers but they are located in the Power Distribution Center in the engine compartment. There are two. The O2 wires, if they touch or are too near the exhaust pipe, can melt. When this happens it is common for the ASD fuse or fuses to blow. If they blow the car will barely run and will have no power. You will also get various warning lights and a CEL. One to many codes will show up as well.

However, after looking at the pictures you posted I would agree with the others, the pipes look awfully small in diameter. What size pipe did you use? Even so, do be careful about how the O2 wires are run to minimize their exposure to exhaust heat.

After the car went into limp mode, I turned it off. When I started back up all the lights turned off but the CEL. So if it were a fuse I think the car would have stayed in limp mode. I'll check them to be sure though.. You're the 4th person that said the pipes are too small. I'm in denial only because I've got hours into the installation, we'll see in a few days. I will move to a 3'' diameter pipe before i drop $2100 on a system.

[AZTVR]

As long as that pipe is 2.5" in diameter, it isn't a restriction.

However, after looking at the pictures you posted I would agree with the others, the pipes look awfully small in diameter. What size pipe did you use?

You're the 4th person that said the pipes are too small. I'm in denial only because I've got hours into the installation, we'll see in a few days. I will move to a 3'' diameter pipe before i drop $2100 on a system.

The way that I read the above posts, people were looking at your photos and saying that the photos made the pipe appear small. They didn't say that it actually was too small.

Like Steve M. said, if you used the same size pipe as the muffler input/output had, I don't see the pipe as causing more restriction than the muffler did. However, I am no automotive or mechanical engineer.

[ViperGeorge]

The way that I read the above posts, people were looking at your photos and saying that the photos made the pipe appear small. They didn't say that it actually was too small.

Like Steve M. said, if you used the same size pipe as the muffler input/output had, I don't see the pipe as causing more restriction than the muffler did. However, I am no automotive or mechanical engineer.

Agree with this. The pictures make the pipes look small, but are they? What size did you use? If you used at least 2 1/2 inch I don't see the pipes causing the problem. Also if on a restart the car was not in limp mode but you still had a code it would not be a fuse.

[RdyPlr1]

Right, it's not a fuse. The pipes are 2 1/2 inch

[ViperGeorge]

Right, it's not a fuse. The pipes are 2 1/2 inch

In that case it would not seem that the pipes would be the culprit. Maybe just a coincidence. Check for loose connections are anything that you may have disturbed when you removed the sills and installed the pipes.

[RdyPlr1]

Will do ^ , I'll update when I find the fix.