NefMoto

Hey guys,

I'm and 01.5 S4 running k03's with piggies, regular cats, and a 3" magnaflow custom catback. I was having issues with a P1556 code that kicked me into limp mode when doing WOT 3rd gear pulls to the top. I was getting thrown into limp at about 6200 rpm. So i scaled back LDRXN_1_A from about 5500 rpm up, until I no longer would get thrown into limp. Problem solved right? well kinda, today I wanted to run all the way through 4th. Well same problem again, thrown into limp with a negative boost deviation P1556, but this time it happened around 5000-5500 rpm. So I guess I have two questions:

Should I just continue scaling LDRXN 1 A back until the issue goes away, I'm currently requesting about 187 @ 5k, dropping to 163 @ 6.7K

Or is it more of an issue with my piggies and regular cats not flowing enough?

I know that I am pretty close to the limit, but it is hard to compare with everyone having different exhaust setups. Is this something that removing the cats, or getting high flow cats would fix?

It sounds to me like you have a hardware issue. Boost leak or a bad N75 maybe. I would say you can rule out exhaust backpressure though.

For reference, 2001 B5 S4 K03s with piggies and 3" catback, I am requesting 187.34 @ 5k and 183.66 @ 67k, however, I do have changes to LDDIMNN.

If it were a hardware issue, would it still be consistent through multiple logs? What could i log to check for hardware issues? Would it be fair to rule out hardware issues if i adjust my load and get sent into limp at a different rpm? I just cant think of what else would cause the ecu to get a P1556 code....

What are you logging with?
How does the car drive before you get limp mode?
Have you pressure tested?
What does requested vs. actual look like?

The car drives great, I never overshoot my requested boost, and actual stays very
Close to requested the entire time. I really don't think I have any vacuum/boost leaks. I'm logging with vagcom. Need another alternative though...

Should get a log showing actual boost, requested boost, and N75 duty cycle.

Need to see if N75 duty cycle makes sense for what actual and requested boost are doing.

If im hitting limp only in 4th should I only be logging that gear? I have the logs from 3rd gear and everything seems fine. I'll have to find some time to log my 4th gear but I would think the duty cycle actual and specified boost would follow the same map no matter what gear?

Kind of odd to assume its doing the EXACT same thing in 4th if you are hitting limp ... only in 4th :P

Stupid question:

Why would you not log the conditions in which you have problems?

No, I understand it makes more sense to log the gear your having issues. When I got the code in 4th I wasn't logging, and I haven't had a chance to go back out and log that gear. I only assume the issues would relate to the same thing because I received the same code in 3rd before I adjusted the map.

So what else could be coming into play? Am
I just reaching a hard limit of my exhaust?

I'll try and get some logs soon but what all could cause an p1556 code?

Don't guess. Log.

Guessing now isn't going to save you time later...