C43 throwing codes and limp mode

[Smoothy75]

Hi All,

I have a 2016 W205 C43, I had the JB4 installed a couple of months ago. Ive only ever tried Map 1 or Map 2, however if I give the car a bit of a tickle on the freeway, I get an engine light up, car goes into limp mode and I get the following 2 codes:

PC431
P0087



Is anyone able to give me any guidance as what I need to do here as it feels as the JB4 isnt really usable.

Thanks in advance

[Payam @ BMS]

Looks like some sort of fuel pressure code. Do you have the green fuel pressure connector from the JB4 connected onto the rail sensor?

[cephaed]

So basically I presume you were requesting more than enough fuel. So the data piggyback returns to the ECU was too low which trigger the limp mode. If that doesn't happen often you can just delete the code in JB4 and get back on your way. Or you can try setting the Fuel Open Loop lower in UserAdjustmentSettings. We don't have the same engine but I hope this helps.

[Smoothy75]

Looks like some sort of fuel pressure code. Do you have the green fuel pressure connector from the JB4 connected onto the rail sensor?

I had it installed by a technician so there's a possibility he may have connected it...I thought it only related to using E85 fuel. I only ever run RON98

[Smoothy75]

So basically I presume you were requesting more than enough fuel. So the data piggyback returns to the ECU was too low which trigger the limp mode. If that doesn't happen often you can just delete the code in JB4 and get back on your way. Or you can try setting the Fuel Open Loop lower in UserAdjustmentSettings. We don't have the same engine but I hope this helps.

I've tried deleting the code and the limp mode does eventually clear after a while of having the car parked up and switched off.
However i tested running Map 1 again after this and it did exactly the same thing with the same codes.

[cephaed]

I've tried deleting the code and the limp mode does eventually clear after a while of having the car parked up and switched off.
However i tested running Map 1 again after this and it did exactly the same thing with the same codes.

How many JB4 wires have you tapped in? obd included?

[cephaed]

I've tried deleting the code and the limp mode does eventually clear after a while of having the car parked up and switched off.
However i tested running Map 1 again after this and it did exactly the same thing with the same codes.

Mind showing me a screenshot of your userAdjustmentSettings page?

[Maverick43]

I’ve had the p0087 code
put my fuel open loop setting at 0 ( suggested by BMS support)
i do have the green wire attached so not sure if that’s why they told me to change it to zero.
have u emailed BMS support ?

[bhodges559]

Did you ever figure out what was going on? I had the JB4 installed on my 2019 C43 and it was causing all kind of codes and limp mode. Still haven't figured out the cause...

[Cannon @ BMS]

bhodges559 please contact [email protected]