Technical U1706 CAN Brake Control Node 1.9 JTD

dancin · Aug 9, 2010

Hi all!

After a very happy stilo motoring across France for two weeks

On starting her up in order to drive off the ferry back to Blightylast night; i get the dreaded 'beep beep beep' and a simple message saying "Loose Connection" the car however drives perfectly except for the speedo doesnt work and a yellow ! in a triangle, the abs light and the handbrake lights are also permenantly on.

So i pull over at the nearest services and get on the trusty Fiat Forum on my phones internet, as always I found much to be getting on with while I waited 2 hours for the RAC patroll. Sadly neither he nor I were able to fix it.

He plugged it into his code reader laptop giving the code:

U1706 'CAN Brake Control Node Intermittent'
after a few clearings and tinkering this then changed to permenant.

Between us so far we have thoughly which I checked twice today back home and after much more forum seraching:

Cleaned D4
Cleaned ABS M50 connector
Cleaned Both ECU Connectors
Cleaned C12 ABS Earth
Cleaned ECU and Battery Earths
Checked and cleaned all fuses and relay conenctors in the engine bay
Checked battery charge and charging
Checked battery earth

I have also been follwing one of Decks guides to HSSB regarding how to check D4 connector by checking the resistance between
M50 pin 40 to ECU Socket A pin 61
and
M50 pin 24 to ECU pin 45.

Sadly both of these came up with a very high resistance (off the scale) so I was wondering if the wiring diagram Decks provided in this guide was the one for a 1.9 JTD 03 reg also?

Also any other suggestions greatly appreciated :worship:

If helpful, the only additional history i can provide is one blown brake light bulb 1 week ago and twice before on starting for 1 second abs failure appeared on the screen and dissapeared immediatley.

Deckchair5 · Aug 9, 2010

With a U1706 and a lost connection warning then you know it's a loss of comms between your ABS unit and the ECU. I'd do a voltage drop test across ABS unit earth C12. You say you have cleaned up C12 and that's good but a voltage drop test will show up any bad earth connection problems there better. Do you know how to do that? If not, have a look in Stilo Guides. Intermittent fault is a pain though so you need to move wiring around whilst testing

Make sure it's nothing simple like fuse F42 ABS unit or even main fuse F1 blown

As it's CAN bus then I'd think you'd need to clear code and disconnect battery for a while and then reconnect for CAN bus nodes to hopefully realign themselves again

Here is JTD wiring diag for ABS unit which I think is very similar to Abarth but best to refer only to JTD one

ABS CAN wiring goes to totally different ECU pins for each Stilo engine size

Here's JTD circled in green,still going through D4 on connection C4 and C5 but then on to ECU connector A pins 28 and 29

So ABS unit pin 40 (lo CAN) connects to ECU connector A pin 28
ABS unit pin 24 (hi CAN) connects to ECU connector A pin 29

dancin · Aug 10, 2010

Thanks for the suggestions Decks!

After following your excellent multimeter guide and instructions to lazzar

With the engine running on setting 200m the multimeter red 05.2v for good earth to C12 connecting ring and exactly the same for good earth to the screw where C12 attaches, does this mean a good earth?

With the engine off i get a voltage of 12.91v across the battery terminals

WIth the engine running i get a voltage of 14.1v across the battery terminals

WIth the engine running and headlights plus fan on I get a voltage of 12.85v across the battery terminals

And for my earth integrity check i get 0.4v

Are these also ok?

Next, as advised I checked F1 - fine

I then checked F42 - eureka!!!!!! A blown fuse!!!!!

Fuse changed and problem has now disappeared

Thankyou soooooooooooooooo much for your help Decks! A well deserved big formal thanks comming your way!

The fiatforum rocks!!!! :slayer:

However,

Do i still need to check the abs connector to ecu pins?

Should i be worried that something could have caused the fuse to blow and hence could do so again?

Also, are there any further preventitive measures i could take?

Deckchair5 · Aug 10, 2010

Ha! Pays to check the easy stuff first

With the engine running on setting 200m the multimeter red 05.2v for good earth to C12 connecting ring and exactly the same for good earth to the screw where C12 attaches, does this mean a good earth?
Not sure what you mean by 05.2v, is that what your multimeter shows? I'd want to see less than 0.5v between the C12 tag and battery -ve

With the engine off i get a voltage of 12.91v across the battery terminals

WIth the engine running i get a voltage of 14.1v across the battery terminals

WIth the engine running and headlights plus fan on I get a voltage of 12.85v across the battery terminals

And for my earth integrity check i get 0.4v
Are these also ok?
All those are good but it's better to check between battery pos and a shiny earth on the engine then you're not relying on battery earth connection

Just log it in your mind that a fuse blew and be ready to step in if it does it again. It's difficult to check for anything wrong when it's all working fine again. A low battery can cause high current and blow a fuse so it might be a one off

Glad it's sorted

dancin · Aug 12, 2010

Thanks again for your help.

I have redone the readings and got:

Battery possitive to engine 12.7v with engine off

And with the engine off and multimeter set to 200m again 00.5v from battery negative to C12 tag.

Are these results better?

Thanks

Deckchair5 · Aug 12, 2010

Yep those are very good

dancin · Sep 13, 2010

Hey again everyone!

Sad news im afraid

On accidentaly selecting 5th gear rather than third, I again recieved the dreaded beep beep beep "Loose Connection" the car however drives perfectly except for the speedo doesnt work and a yellow ! in a triangle, the abs light and the handbrake lights are also permenantly on.

- exactly the same symptoms as a few weeks ago.

So I immediately check brown fuse F42 (7.5A) and its blown again, so I replace it, only for it to blow again immediately

Any suggestions would be very much appreciated, as im stumped :worship:

Deckchair5 · Sep 13, 2010

OK, time for some further investigations. Good news is it should be easier to trace if it's permanently blowing fuses than when it's an intermittent fault

You have a short circuit to earth on the downstream side of Fuse 42, so using a multimeter, find out which side of the fuse holder for F42 is not giving 12v with fuse removed and ignition on. That's the downstream side.

Now ignition off and set multimeter to resistance and check the resistance figure from that point to battery earth. It's probably very low, near zero and that's the short circuit to earth and causing your fuse to blow

So, ideally, you want to be able to permanently and reliably attach your multimeter leads to those points and then watch the meter as you move things like wiring and connectors
Remove the ABS connector M50 and see if the resistance gets much larger. If it does then the short circuit is in the ABS unit

If it stays the same then the short is in the fuse panel B2 or the wiring to the ABS connector

dancin · Sep 13, 2010

Hey Decks!!

Thanks for the quick reply

I have just been out and identified the down stream terminal (its the one at the bottom) but it was giving 14v with the ignition on, is this ok?

With the ignition off and multimeter set to resistance (200k setting) I connected the black multimeter connector to the end of a jump lead (using to extend from the negative battery terminal) and the red of the multimeter to the downstream of the fuse connector.

With M50 connected I got 14 and with it disconnected it climbed in increments of 10 to around 50!

I left all the other connectors connected to the battery negative and just cliped it on top, is this correct? Or should I disconnect them all first and have only the jump lead on the battery negative terminal?

https://www.fiatforum.com/attachment.php?attachmentid=81945
Thanks again for all your help

Deckchair5 · Sep 13, 2010

I have just been out and identified the down stream terminal (its the one at the bottom) but it was giving 14v with the ignition on, is this ok?
Should only be 14v on upstream side with ignition on. Are you saying you're getting 14v on both sides of the fuse holder? If so you might need to remove Fuse F1 as that is providing power to M50 connector as well

Never mind. Next check I'd do
Battery disconnected
F42 fuse out
M50 connector reinstalled if you removed it
Check resistance between downstream F42 and M50 earth point C12
See if it alters when you wiggle fuse panel B2 or connector M50

dancin · Sep 13, 2010

No, sorry 14v from the top one and 0v from the lower connector for the fuse connector.

Ok cool, I have just tested resistance on 200k setting from the downstream port to just the tag of C12 (with it and the nut removed from the car body) and i got a consistent 12, which did not change with wiggling the connected M50, the fuse pannel or the C12 wire.

Is this correct or should I measure it at the tag while screwed onto the car body?

Thanks again

Deckchair5 · Sep 13, 2010

Well with 12k ohms resistance to earth then it shouldn't be blowing fuses
Current I = V /R so I= 14/12000 A and that won't blow your fuse.

Is this correct or should I measure it at the tag while screwed onto the car body?
That's ok, it will make no difference for this test if it's not attached

It should all work and not blow fuses from the figures you're giving me. Sounds like intermittent fault

I'd check out your maxi fuse F1 connections for poor fuse blade contact etc as maybe an intermittent supply from there (which is the main feed for unit M50) is putting an overload condition onto F42

dancin · Sep 13, 2010

Thanks Decks!

How do i find Maxi Fuse F1?
Also, would you suggest I replace it and check its connections?
Is there anything else I can check with it???

Deckchair5 · Sep 14, 2010

Maxifuse F1 is on B1 panel whch is right next to battery
I would just inspect the fuse contacts both on the fuse and the holder

dancin · Sep 14, 2010

I think we may have hit the jackpot

Maxifuse F1 has a slightly snapped off plastic surround, i guess due to a forcefull replacement of the battery cover. The fuse pins are also slightly bent and on one side the contacts in the fuse slot seem to be shorter than the other!

I have bent as best as i can the shortend contacts but im not sure wether this is a permenant fix, would you suggest replacing the whole fuse pannel? Would this be easy?

Thanks again Decks! Your an absolute legend :worship:

Davren · Sep 14, 2010

It's possible to remove and dismantle the fusebox. If you do, be very careful. all the fuse and relay contacts are seperate inside the box so if you take them out, remember where they go.

By looking at the top of the fusebox, you should be able to see if there's a spare set of maxifuse contacts. i.e. metal contacts in a position where there's no fuse. If there is, you could fit those in the positions of your faulty contacts.

Once the contacts have bent or been damaged, it's very difficult to get them back to the correct shape and tension so they make good contact with the fuse.

dancin · Sep 14, 2010

Thanks

Has anyone done this before and made a guide or something similar by any chance?

Also, is it likely that I will balls the whole thing up if I attempt it as I dont have much experience with electricals?

If I do mess it up, is it simply a case of getting a new one from a scrappy and just swaping them over?

Davren · Sep 14, 2010

I've done mine to clean out water and corrosion. Didn't think a guide was neccessary because it's just a matter of being careful and remembering where all the contacts go when you reassemble it. I had them all spread out in order on the kitchen table.

No guide is going to show you how to be careful or remember things.

If you mess up, yes you could get one from a breakers but there are several different versions. You would need one from a JTD of similar age to yours.

dancin · Sep 14, 2010

Thanks!
Will see how long my bodge job holds out, first time it goes again, il give it a crack or wait till I get a free weekend

A big thanks to everyone for all your help, will let you know how I get on

dancin · Jan 30, 2011

PROBLEM SOLVED!!!!

FIX:

After 6 months of searching ive finally found the problem!
A quick reminder of the symptoms:

Beep Beep Beep "Loose Connection"
Preceded by blowing of fuse F42 (steering column)
Replace fuse F42 - temporary fix for an hour up to a week
Fault codes given as above!
Before fuse replaced: ABS light, handbrake light etc. constantly on and no speedo!

Also;
Beep Beep Beep rear number plate bulb blown
Alarm sounding randomly for no reason most times when set

Final symptom;
Turned ignition off but every light on the dash illuminated on despite the keys being in my hand!!!!

The only fix being removing unblown fuse F42

On removing the large connector to the ABS ECU and noticing a strong smell, I noticed smoke emanating from beneath the ABS ECU so quickly removed fuse F1 and phew the smoke stopped!!!

EUREKA!!!!! :idea:
There is a large wiring loom which enters the engine bay beneath the ABS ECU, however, Fiat in their infinite electrical wisdom have made this loom too short so it very slowly rubs through the bracket which holds the ABS ECU in place resulting in intermittent electrical faults listed above!
Fortunately I found this just in time before a major car fire

I urge everyone to check very carefully that there loom is not rubbing here too, even without symptoms as some strategic electrical tape could save a lot of hassle and fire!!!

Simple fix was a tow truck to my local auto electrician who replaced this section of loom for £100!!

All problems now absent for 4 weeks

Technical U1706 CAN Brake Control Node 1.9 JTD

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