[Bryans86]

My friend drove 170 miles away to buy a jb4 , meth kit, turbos etc for his 08 535i. Against my recommendations he tried installing the jb4 at the sellers house . He disconnected the battery and installed it only to have it crank no start . It was throwing a communication error cf33. That pulled the jb4 and Tried to reset it but immediately comes back. Tried letting the car go into sleep and that whole process with no luck . Eventually the i drive shut off and the car got towed . I scanned the error memory with inpa and got a ton of communication errors and eventually turned the idrive back on by taking it out of transport mode. But eventually I was unable to even pull the error codes from the car because it wasn’t communicating. Any idea on what to try next . I Suggested he send the ecu and key fob in to have checked

[pbonsalb]

I would have guessed he ran the battery down. Low battery causes all sorts of trouble on these cars. I installed and removed one twice without issues on an E61 535xi and a similar piggyback twice on an E90 M3.

Bent pins. Broken pins. Harnesses not seated. The power wire splice not correctly done or located. Old firmware. Wire is pulled out of connector. Wrong map or wrong settings. Seems like the seller had the JB4 customized for meth and larger turbos that the buyer had not yet installed.

There are some reports of the footwell module being damaged from voltage spikes from reconnecting the battery.

A likely unrelated comment — these cars suffer blocked sunroof drains that lead to water pooling in the trunk under the spare tire where several modules are sandwiched in foam. Water can also drop down the right rear over the fuses. There are DIY fixes you can search for. I recommend the one that uses an initial section of larger tubing. Also pull out the plugs in the very bottom of the tubes. You do not want to suffer this problem….

[123i]

Think he bent/damaged some pins? Or maybe didn't put the connectors back in the right place (not sure if that's possible or they are different enough to not swap)

[Bryans86]

I was wondering about the firmware on the jb4 but I would think once he pulled it out and put back to stock it would’ve started. I’m looked briefly at the pins they all looked ok but I’m gunna go double check now. As well as get a list of codes. One thing that I’m stumped on is the second I click read error memory the light on the connector shuts off and it can’t read the errors. But I was reading them fine hours earlier. The dcan cable will light up again if I unplug and plug in . But when ever I try doing anything is shuts off . But I can pull codes with a snap on scanner . 🤔

[Bryans86]

So now I can’t connect to the car and read the error codes and also the fuel pump just runs continuously with the ignition on. So I’m thinking it can’t read the fuel pressure? I’m going to install the jb4 tonight and try putting to stock settings and update the firmware unless any other ideas

[pbonsalb]

Hopefully you will find something wrong during the install. Have the JB4 instructions printed in color or open on your laptop. Count pins from the correct end and tow or do whatever you need to be 100% certain when doing the splice.

[Kponti]

Been there, done that on a 2010 535i. Ended up replacing the alternator, battery and reprograming the ECU from scratch to get the car running again.

In my case, the JB4 was already installed for over a year, I was parked waiting in the car when I had this brilliant idea to update the JB4 firmware while I waited. Mind you I was 4 hours away from home. Was a very expensive tow back home the next day!!!

[pbonsalb]

Good idea to use a power source when programming or flashing or coding. Not sure if that was the culprit, but insufficient voltage is known to cause problems.

[Bryans86]

So update . I hooked the jb4 back into it and the only way to get the jb4 powered is by running a jumper wire . Usually I can just tee into the green plug up front and now there’s no power there now . Also the jb4 is reading zero for pressure from the low pump . But I can physically hear it turning on with the key on. Any ideas ?

[Bryans86]

So I’m going to pull out the CAS module and send it with the DME and a fob for testing to see if the issue is coming from the dme. I did test the mosfets which all appeared the same ( in relation to continuity) I thought possible the battery sensor died but I tried unplugging it and no change . He did mention the negative snapped back on upon connecting the terminal to the battery. He also said it was showing a warning for large battery draw on the drive down. Could the alternator be bad causing a ton of error codes and not starting even when it shows 11.6 +\- during cranking

[pbonsalb]

Warning for large battery draw could mean the alternator has failed and the car is running off the battery. Won’t drive like that for more than the reserve time — an hour at most. What would a failed IBS cable do?