JB4 - EPC Light Issue

Nov 13, 2019
Hi All,

So I decided to take the plunge and purchase a JB4 which i spent Tuesday fitting.

Managed to get it all sorted out, although the bluetooth module didn't seem to get picked up by two separate phones but i've given George at BMS an email about that and he's sent out a chip that should sort it. (Apparently my unit could have missed the rev 3.7 update for the newest bluetooth module to work.)

Anyway, I'm running the JB4 currently in what would be Map 1 but I've had some EPC issues.

First Drive around 30 minutes:
I went out on the first test drive and all seemed fine, was boosting fine and power delivery was strong and smooth.

Second Drive: 15-20 minutes fine, then pulled off from some lights and EPC comes on with ACC disabled (both lane assist and front assist) and Engine Revs limited to 4000. No boost at all. At the next set of lights I restarted the car and the EPC light went away.
Got home checked the AFR cable was secured, OBD secured and Plug B + C. + D.. all seemingly fine?

Third Drive, this morning around 40 miles:
Was fine until about 10 minutes from my final destination with the EPC light appearing again but this time with ACC Disabled, Revs @ 4000 and Start Stop error. I drove the last 10 minutes, turned off the ignition and removed the OBD port cable as I'd read that can solve the issue. Drove home, within 10 minutes had the EPC light on again with the same issues.

I'm really confused as to why this would be happening, car was stock before but I drive it fairly hard most of the time if i'm being honest and have never had any of these issues.

As I say I can usually use the car for around 15-20 minutes with the JB4 perfectly fine before I get these warnings pop-up, and due to the bluetooth not working I can't check the logs in the JB4 app to see what's going on!!

Not sure if I should leave it in place or take it out and wait for the chip from BMS so i can check these codes over - i've since emailed George just waiting for a response... just wondering if anyone has experienced this?

Sorry for rambling, just wanted to add as much info as possible! Any help appreciated.

Car: Leon FR 1.8 TSI