Di2 junction Box - Rear derailleur stopped working

sthel007

Looking for help.

1st problem.

Di2 rear derailleur stopped working. Won’t change. Front mech working fine. When I press and hold right (rear) shifter, junction box lights up green to show full battery. Same with left shifter. I have removed tape and checked the connection is fully home.

2nd problem.

When I press and hold the button on the underside of the junction box...nothing. Cannot enter adjustment nor recovery mode. No light comes on no matter how long I press and hold.

Any suggestions/help please.

pilot_pete

Plug in your charger and open e-tube software on your pic/ laptop. Make sure the system is recognising every item and apply any software updates. That would be my starting point after disconnecting and reconnecting the battery.

sthel007

Thanks. Will try the disconnecting/reconnecting the battery first.

I can’t connect to e-tube as the junction A button needs to be press/hold until the light flashes. The problem is the light won’t flash when I press/hold, so I can’t connect to e-tube.

Any further ideas?

ibr17xvii

sthel007 said:

Thanks. Will try the disconnecting/reconnecting the battery first.

I can’t connect to e-tube as the junction A button needs to be press/hold until the light flashes. The problem is the light won’t flash when I press/hold, so I can’t connect to e-tube.

Any further ideas?

I'm certainly no expert as I've only just got Di2 myself but I don't think you need to touch the junction box to use E-Tube.

Your Di2 just needs to be awake so just press a button or move your front mech if you know that's working OK.

skwarczek

Sounds like its in crash protection mode

Unplug rear derailleur, wait 20 seconds, plug back in

sthel007

Thanks for suggestions.

I have unplugged rear derailleur and waited but nothing happens.

I have now taken off the rear mech, bypassed the wire running to the back and plugged it directly into the junction b box in the down tube.

Still nothing. Front mech works fine. Battery test using the rear shifter also works fine, so signal is getting through.

Dead motor on the rear mech?

pilot_pete

You need to plug it into e-tube to ensure it is being recognised. If it’s not recognised in the system it won’t work.

Plug your charger into the junction A and plug it into your laptop. You do not need to press any buttons on the junction A to get it open. Just open e-tube software (ensure that is up to date) and interrogate the system to see what components are recognised. You may well find it is not seeing your rear derailleur. Sort that and it will probably work.

I also suggested unplugging the battery and re connecting it. Do that first as it may sort the problem.

pilot_pete

I am assuming all the connections between shifter, junction A, junction B and your rear derailleur are all secure, with no faulty wires/ connections. You will need to plug in a SM-PCE1 or newer SM-PCE02 diagnostics tool or use trial an error with a known good cable to isolate the fault further.

pilot_pete

Just plugging the derailleur into the junction B using another cable will not necessarily fix the problem - it may still not be recognised in the system until you use e-tube project software to ‘make’ the system find it.

pilot_pete

From what you said in your first post.
1. Shifters are connected and signals are being received by the junction A.
2. Junction A to junction B connections are working.
3. Junction B to FD is working.
4. Battery to junction B is working.

So, there is either is a connection issue from junction B to the RD (seems unlikely as you have tried two cables). Or your connection to the RD is faulty (did you use the tool and make sure it ‘clicked’ home?) And the same with the cable(s) into junction B? If so, the derailleur could be in crash mode - was it knocked/ did you crash/ hit it and then it stopped working? Alternatively, and most likely in my opinion, is that it just isn’t being recognised by the system for some reason. I have mentioned above how to sort that in e-tube.

Finally, it could be a faulty derailleur, or a faulty port in junction B, or a faulty cable (which are all less likely in my opinion).

You can reboot everything by disconnecting the battery and then reconnecting it, not just disconnecting the rear derailleur. The circuitry is in the battery. Do this. And then you really need to use e-tube software as otherwise you are potentially replacing components unnecessarily, when all it needs is a ‘reset’ to get everything connected again.

If all that fails, either get it hooked up to a diagnostics tool and read the error codes, or borrow another di2 rear derailleur and hook that up physically and through e-tube to see if that works.

sthel007

Cheers Pete.

In answer to your questions...

Your points 1-4 are all correct.
I used the tool to make sure a good connection was made. All cables fully home.

I didn’t crash or knock the RD. I was climbing a hill and tried to change down a gear and there was no response from the RD.

I have taken the battery out of the down tube and fully disconnected the battery.

The thing I haven’t done is use e-tube software for 2 reasons:
- I don’t have a Windows machine
- I don’t have the right cable to connect to my phone.

Having read the connection instructions for e-tube to my phone, it does say I need to press the button on the Junction A and wait for the lights to flash. I get no response at all when I press the button.

One other thing I wanted to try was borrow another Junction A, as it would be easy to plug in the 3 cables. Do you think is a good idea?

Thanks for your help.

ibr17xvii

sthel007 said:

Cheers Pete.

In answer to your questions...

Your points 1-4 are all correct.
I used the tool to make sure a good connection was made. All cables fully home.

I didn’t crash or knock the RD. I was climbing a hill and tried to change down a gear and there was no response from the RD.

I have taken the battery out of the down tube and fully disconnected the battery.

The thing I haven’t done is use e-tube software for 2 reasons:
- I don’t have a Windows machine
- I don’t have the right cable to connect to my phone.

Having read the connection instructions for e-tube to my phone, it does say I need to press the button on the Junction A and wait for the lights to flash. I get no response at all when I press the button.

One other thing I wanted to try was borrow another Junction A, as it would be easy to plug in the 3 cables. Do you think is a good idea?

Thanks for your help.

If you don't have a Windows PC you can still access E-Tube on a Mac by using Virtualbox. Shane Miller on YT has done a video on it. Won't work on iPhone or iPad though.

I only have a Mac & don't have the wireless module so this is the way I update firmware & change settings etc. It's a bit clunky but gets the job done.

sthel007

Update. Connected it to e-tube. Rear derailleur not showing up.

Connected friends RD cable to my bike. Connected to e-tube...also didn’t show up.

Connected my RD cable to his RD. It worked.

Conclusion - RD failure. Probably the worst/most expensive result.

😞

shirley_basso

Yeah I had that, was very random.

Sadly there is no way to repair it, as you can't access the electronics.

I think the best price I have seen is £200 for a R8020 series mech.

ibr17xvii

Bummer.

I got mine a while ago now from PBK for £170 but they seem to be £200+ now.

Stick your old one up on eBay, someone will buy it. Even if you don't get much for it you can put it towards a new one.

sthel007

I assume the R8020 is backwards compatible with the R6800?

shirley_basso

100% yes - I had the exact same issue as you and have replaced my 6870 with R8020

May need fully up to date software.

sthel007

Thanks Shirley.

As you can see from the photo, RD is not showing. I am updating the firmware on the components so they are ready to receive the new RD.

BetterShifting_Terry

R8050, yes ;-)
(not R8020)