[davidoh1989]

Hello

So i have decided to go with JB4 on my car.
I installed the JB4 with a friend and the car keeps going on limp mode (reduced power). So i thought maybe we didn't do it right.
I take it to a professional shop, and my car is still having the same issue.
I think it's not the JB4 issue because I tried on my friends JB4 and it worked for like couple of second. After giving some gas, same limp mode comes on.
My friends JB4 works on his car but not on mine.
My car is still in the shop trying to get JB4 installed, so I even told the mech to do a diagnostic without the JB4, and the only code is the o2 sensor caused by the aftermarket DP.
The shop my car is actually one of the most famous shop in Atlanta, so I am sure they know what they are dealing with.
Anyone have any clue what it could be?

[weehe126]

Probably a bad power or ground source.

[BrianT335i]

I changed my spark plugs and coils and they seemed to solve the problem

[Manberg]

No codes no problem, cant fix a car that works. Does the car run fine without the JB4? If it only has an O2 code and runs fine with out JB4, then its a JB4 issue. Make sure you have all your user settings correct, double check connections, make sure the pins are ok in the connectors and try checking pin drag on the female side. Like stated before, make sure your ground in solid.

[dannyle27]

wrong firmware?

[Mike@N54Tuning.com]

If you can't figure it out take photos of the install and either email them to BMS tech support or post them to the BMS tech support forum for help.

Mike

[bmw_hub]

make sure you have auto clear off as the JB4 will clear all fault codes if left on

[davidoh1989]

I also noticed that JB4 control actually works, and the needle swing also works.
So I am thinking it is probably not the JB4 that is not working.
My car has been in the shop for like almost two weeks, and they are still working on it..

[Manberg]

What symptoms are you experiencing? just the light? low power? rough idle? hesitation?

[MR.BLUECOLLARMAN]

You need to diagnose if the issue is the car or the JB4. Point us in the right direction so we can help

[davidoh1989]

So i just got an update from the shop.
they think Tmap sensors are bad on the car, so they are going to replace them.
Symtoms while I am experiencing with JB4 is the reduced power light (think its called limp mode?). I didn't drive it around with that light on because I just thought driving with that light on is pretty bad for the car.

[Cory S]

Originally Posted by davidoh1989

they think Tmap sensors are bad on the car, so they are going to replace them.

VERY slim chance of this.....

[weehe126]

Originally Posted by Cory S

VERY slim chance of this.....

Agree, if you get limp mode only with the JB4 installed, it's related to the JB4.

[Mike@N54Tuning.com]

Originally Posted by davidoh1989

So i just got an update from the shop.
they think Tmap sensors are bad on the car, so they are going to replace them.
Symtoms while I am experiencing with JB4 is the reduced power light (think its called limp mode?). I didn't drive it around with that light on because I just thought driving with that light on is pretty bad for the car.

Failing to work with BMS technical support on JB4 install related issues can lead to an expensive wild goose chase. Especially so with inexperienced installers.

Mike

[davidoh1989]

sent the jb4 to bms for check up.. just in case

[Miilano]

Any update?

I'm having the same issue, I suspect mine could be due to the ground wire.

It's just a guess however, I'll hopefully time to diagnose it further this week. Car runs great without the JB4 installed and was in fact working for couple of months until the problem occurred.

[davidoh1989]

jb4 issue. had to send it to bms and it works like a charm.