[meadowsdb]

So, I have had a JB4 on my car for months now and all has been awesome. I typically drive on MAP 2 and run an e-30 fuel blend.

Today, on a drive from Phoenix to LA, I got into a "friendly celebration of speed" with a new GT500. We did probably 5-7 hard pulls over the course of 15 minutes of highway driving. During the last pull, I got a "drivetrain malfunction" light, with a "reduced power, driving still possible" warning.

Obviously, I chilled out.

The car ran fine for the next 200 miles home, albeit in lower power mode-Though I was driving quite gently. I also disabled the JB4 for safety. When I got home, I checked the codes on the JB4 and got the above feedback.

I cleared out the codes, drove her around the block, and all seemed fine.

Thoughts?

Thanks in advance!!!

UPDATE----Drove her around today, on MAP 0, for about 2 hrs. Did a few WOT pulls on the interstate. Nothing. Ran perfect and pulled great. If this keeps up for the next day or so, I will reload MAP 1 or 2, and see if the issue comes back. Seems to me that if something was PHYSICALLY damaged, broken BOV, Tubing, ETC, the problem would be consistent...

Thoughts?

[ctelimad]

This is not uncommon on map 2 especially with competition models
Probably overboosted and the car went into limp mode to protect the engine
Sometimes when u push the car too hard that happens
I had jb4 map2 on my 2020 M8 non comp and worked really good for almost 3 years with not a single problem
Now i bought a competition coupe and i put it on map 2 and the car running really good but when checking the codes i found a hidden code related to knocking on cylinder one although no cel and the car driving fine
I contacted terry and could not find a problem with my logs
Now i am map 0 then will switch to map 1 if no more hidden codes

[meadowsdb]

Interesting.....even though the code said BOOST LOWER THAN EXPECTED? I have read that is often indicative of a boost leak somewhere.

[Beemer5to3]

Originally Posted by meadowsdb

Interesting.....even though the code said BOOST LOWER THAN EXPECTED? I have read that is often indicative of a boost leak somewhere.

It’s the way the JB4 and other piggy back systems work - it effectively makes the ECU tell the car to produce more boost, as it fools the sensor readings into telling the car it isn’t producing enough, hence the low boost warning.

[meadowsdb]

Weird....OK, so it COULD be meaning that under the hard highway pull, the turbos weren't able to get up to the levels of boost that the JB4 was demanding of them, so the car's ECU and boost sensors THINK they are getting BOOST LOWER THAN EXPECTED?

[VerryNiiceM8]

Any updates on this issue? Been having non stop drivetrain malfunction with JB4 installed.