Tubi Headers, Tubi test pipes, Bigg Daddies Catted O2 extenders....P1448 code

Skipp - you are likely close and at the home stretch. Remove the bypass and send it to me and I will test it.

You have gone this far my friend.......

If I lived close, I'd be at your house now

 

After two months, I'd be frustrated too. You've got a competent shop, or two, in your area. Let them deal with this, as this is what they do all day long.

 

I have to agree to the sentiments of just packing it in but let me tell you what I finally did:

The dealer convinced me there wasn't sufficient back pressure from the Tubi muffler and Hyperflow Cat system and he offer at no charge to put a stock muffler and and my rebuilt OEM cats on the car and test it for a year after its major at 23,000 miles. I went with NO CEL for a year in this configuration.

Since I loved the sound of the Tubi and knew I could get it in Bypass mode, and also because I am an engineer in gas dynamics in the aviation business, I put two choke washers downstream of the Cats to simulate the back pressure provided by the OEM exhaust with the Tubi installed. I missed the sound at idle and my wife said the car still sounds like **** at idle, but it was amazing in full bypass in the I-90 tunnels here in Seattle.

I drove it 6 years in this configuration with no CEL until I sold it and got a 458 Spider which sounds almost as good!!

There are two significant things you should do; 1.) put in the Dave Helms gold pin kit for $2500 which will stop the fault messages; 2.) Put in the extension washers for the O2 sensors to take them out of the unstable gas stream of the CATs.

Finally recognize that the F355 has a flywheel that is too small for the engine, and depending on the timing job you get from the belt service, your engine can become dynamically unstable and confusing the Motronic as to how much fuel to put in it which produces an "out of spec" fuel mixture as measured by the CAT, which can amplify the engine's instability.

You may be interested to know, I loved my F355 Spider and thought it looked and sounded amazing, so much so, that I spec'd my 458 Spider to look exactly like my F355. Do what I suggest and you will be happy with it for years.

 

Hi Dave,

I have a 98 F1 just like Skipp. My headers are stock, hyflow cats and a custom exhaust (no muffler). I don't have these issues with my car.

I don't have the GCK and I never will. I respect your post but these cars can be fixed properly without work arounds and will run with no CEL's or SDL's.

I believe Skipp is very close to a solution. Sure, it can get frustrating after trying different methods and not solving the issue but I'm betting if Skipp takes a break and a breathe, he will be back at it and can solve this (especially with some of the great help from members here).

 

He didn't have this issue before he changed the headers and eliminated the cats and went to straight pipes. I run hyperflows and tubi exhaust like you had and do not have this issue.

I was thinking that you may be onto something with the straight pipes though. Maybe the pipes alter the exhaust flow such that the temps as seen at the bypass TC are now out of range and thus the CEL. Given that the only change he made was headers and pipes and he's gone through the alert system components throughly, it makes sense that it is something in that new exhaust configuration. M

As David said, it may be time for someone who had the equipment and ability to see what's up and advise. He did have the exhaust installed by a professional shop so it would make sense to go there first.

I know others have run straight pipes without this problem but then I run your set up with no problems.

Maybe tie off the bypass TC and cap the Bing if the bypass has been determined to be working?

 

He does have extenders with mini cats also. Big Daddies

 

Bob, his code is related to the function of the bypass, not the temp. at the flow path. Also, running test pipes results in lower EGT since less restriction....

 

The TC is what tells the motronics whether the BP valve is opened or closed by monitoring the exhaust gas temp. The 1448 code is generated by the TC/SDECU system as is 1447.

The system will throw SDL and I would think this CEL as well if the voltages generated by the TC/SDECU are out of the specified range, high or low. I know this from personal experience with transmitters that start at a below range voltage and throw SDL until warm and in range.

 

Yes, I am aware of this.

Yes, but I believe the Motronic has logic that differentiates the EGT of the bypass flow path vs the proper operation of the bypass valve, hence the reason for 2 independent codes.

 

There is one output signal wire from the SDECU and one voltage. The information regarding the function of the BP valve comes from this one voltage reading. This voltage reading is generated by TC/SDECU in response to the exhaust temps. The 1448 code is determining whether the BP valve is working or not based on the temp of the exhaust as transmitted by the TC/SDECU.

I am postulating that the flow of the exhaust has been altered by the test pipes in such a way that the temp at the BP TC is now indicating a non functioning BP valve because of the temps that the TC/SDECU are reading.

 

Bob, The Motronic is like a PLC which I has experience with. I don't know the ins and outs of the Motronic but it certain could have the logic to report something based on a sign(s) over time. So, just be cause the TCU's have only one signal wire does not mean that signal can't get interpreted by the controller based on what is being output. We already know the TCU does not just send and ON/OFF signal or a 1 or 0

Can we agree on that?

 

The motronics is interpreting the output of the BP SDECU to determine if the valve is opened or closed. It is the TC/SDECU system that is providing that information.

Again, possibly in this situation due to the custom configuration, there has been an alteration of the exhaust in such a way that the temperatures as read by the BP TC/SDECU are telling the Motronics that the BP valve is faulty.

 

With the bypass closed, the post bypass TC will not see any different temperature related to Skipp's Tubi headers or test pipes - (Door Closed...). When open, perhaps.....

 

The 1448 just says BP circuit issue. It doesn't specify if its reacting to a low temp (closed) or a high temp (open) issue. It is just saying it doesn't like what it sees. If that signal line was tapped we would know for sure.

The BP may be opening and closing because that is responding to a vacuum/electrical signal. The SDECU is just amplifying and transmitting what the TC is sending. As I said, I have seen errors in this system for a low voltage reading as well as high voltage.

The back pressure comment in the earlier post regarding the posters hyperflow/tubi setup resonated with me as a source of this issue due to the unrestricted nature of the test pipes altering the detected temps at the BP TC such that the motronics sees a fault there.

It is just a possibility.

 

Ding, ding ding....We have a winner, Bob. I see this code from time to time and one can be easily misled by taking a too literal approach to the "information" a generic code reader presents.

When using the factory tools, the 1448 code will reveals all sorts of temperature data (and perhaps more faults) relating to what the TCs are reporting. These temps, coupled with an understanding on how the Motronic system actually works, will tell us what exactly is going on. Otherwise, which I have said in the past, we are simply guessing.

Send the car to a pro and be done with it...

 

It should be noted that this issue started after a "pro" worked on the car

Just say'ing......

And, if we are not an electrician, we should never change a light bulb or do any wiring in our house....

If we are not a plumber, don't go to the hardware store and fix an issue with a toilet...

Let's not cut our own grass unless we are a lawn contractor.....

I commend Skipp and others like him that dive in and try to solve a problem along with many folks here (non-pro's) like Drbob and alike that make (educated) "guesses" to help solve a problem.

That's what a forum is all about

 

Two months of guessing and frustration, that's what this post is about. It can continue to be a science project or the owner can enjoy the car. He's made his choice clear and based on the insufficient technical information I've read, he's making the correct decision.

 

I've just read through this entire thread and unless I missed something it hasn't been established that the by-pass valve is actually working under dynamic conditions. I read where it was tested at idle by disconnecting and connecting the vacuum line, and read that the car gets loud at WOT, but no actually conformation that it is operating correctly. Did I miss something?

 

John, you are correct. I spoke with Skipp and he only tested at idle. I gave him a few ideas to try.

 

It's taken 24hrs to be able to continue with this. Thanks again to those who have been encouraging with this issue. After all, that's what this forum is about.

I'm perfectly in tune with what my strengths and limitations are, and when I get over my head or at the end of my rope, I'm happy to go professional. It's not a question of cost, rather, about the various aspects of this hobby and satisfaction. I'm confident that I'm able to do the basic servicing of my cars and in many cases more knowledgeable than the supposed "professionals". I'm very confident that I do a more conscientious and thorough job as well.

With that said, I spent about an hour today with my mechanic discussing the situation and feel much better that I have a partner in this. Together, we will find the answer in the coming week.

I think the ideas from this forum will eventually be the answer. I'm just not sure which one at the moment......

We looked at the OEM headers vs. Tubi headers and they flow differently on the exit paths. He noticed the difference, not me. Maybe this flow difference is causing the issue. I'm also goin to talk with Capristo to see if they've experience this 1448 with other folks.

We will be testing the bypass function, etc. and the wiring going to the ecu for shorts. Another thought was that the main ecu could have been permanently damaged by the original broken thermocouple to the BP which was rubbing on the heat shield and may have shorted out and damaged the ecu.

I can tell you that the mechanic is very competent and ex-factory. I feel much better at this point,

Worst case, I believe I could ship the ecu to Fabspeed to program this bull#%^} away.

Thanks again to my friends here and I'll be sure to share the struggle for those who come after me.

The car is running better than it ever has. Probably from all the use it's getting from this diagnosis!!!! Miles do equal a better running car

 

I saw that you offered to send him an OEM BP valve to try. Seemed reasonable.

 

That was a very nice offer from Dave. I still have my original for testing purposes.

 

I'm declaring victory over the Bypass P1448 code !

The solution is Goth's TCU bypass box. It's taken all of 2016 to get headers and test pipes to work with no codes. Was about to throw in the towel when Goth came through !!
Many thanks to Goth, Drbob, and Daverocks for the insight and support over these many months of frustration.

Case closed !