Can anyone help? I've read so many posts and I am getting nowhere with this one. The car is now needed for a driving test and of course with the engine check light on it will likely not be allowed and with the new MOT rules I guess it will soon fail that too in October!

Error codes are;
U1734
Battery Sensor (IBS)
No node on B-Can
B1047
LIN Serial Line

My guess is the IBS is not talking to the BCU. There are no other errors on the car and the battery has just been replaced (various IBS reset methods from forums used to set IBS have been used)

With or without the sensor connected the car errors B1047 immediately on clearing fault code and 2/3 mins after start the U1734 error will come back, along with the triangle and start stop light and start stop unavailable message.

I got hold of a second IBS, but same results, but can't be sure second one was working, my local dealer could not get a new one anytime soon and they are £122 + vat.

I've tested the power line to IBS, reads 12.67v when car running (car reports 13.9) I have tested the 2nd (data?) wire as far back as I can to the loom in case of breaks.

Does anyone have a wiring diagram? I'd like to test the wire back to BCU if I can.

Anyone have any clues for me?

Many thanks,

Neil.

When you say engine check light, so you mean the triangle or engine symbol(a totally different issue)
I suggest turning off the SS each time you drive the car?

Yes sorry the yellow triangle comes up.

I have tried to turn it off on start up, but the error message still reports and the warning triangle comes up.

Do you know the car..? Years of trouble free driving.

these things dont tend to 'just happen'..
There is normally a chain of degradation

Niggles before this..

Battery sounds fair.. guessing youve boosted the earth cabling already.

Any major work carried out recently?

Has the car had a new engine earth strap? If not it WILL need a new one. About £5

Unfortunately I do not know the history of the car, but pretty sure its never had an earth strap fitted.

I've just read the 500 has 2, I guess I should do both, any particular supplier recommendations?

Many thanks,

Neil.

Just do the short one to the gearbox, 250-300mm long 8mm holes and 25mm2 should be more than enough

John, thank you for that advice, it certainly did need replacing, turning to dust when I flexed the cable! Found suitable at local parts shop and replaced. Unfortunately it did not fix the start stop issue.

Not having a good day, took a trip to local Fiat specialist, but his Witeck adapter broke when he plugged it in, the snapon unit did bring back an intermediate bluetooth error and I am told the gear shift indicator is rather hit and miss. Not sure if that will help or hinder!

Many thanks,

Neil.

The SS may require some time to correct IF this was a contributing issue but suspect it won't help that much, but will help starting etc.
Your car a manual or auto?

I suggest if you don't use the Bluetooth unplug it behind the door panel rear passenger side, its known to fail and cause battery drain issues.

I'll see if I am allowed to disconnect the bluetooth!

The car is a manual.

More researching over the weekend has given me the same error combination on Alfa forums, mostly pointing to an issue with the IBS, I've now tried to swap with a unit from a breakers, same errors, but I was not sure if the unit was working or not.

I decided to see if the LIN wire still has a good connection back to the body computer, but I can't find a wiring diagram for start stop in my documentation! If anyone has the wiring diagram it would be greatly appreciated!

I've also built a LIN sniffer from an Arduino, just waiting for the interface chip, so I'll see if there is any signal on that wire soon.

Any other ideas greatly appreciated!

Many thanks,

Neil.

So a trip round a few garages by my partner produced no answers and no one prepared to try and answer.

It did however produce 2 quotes to remove the warning lights permanently from the dashboard.

Is this the latest? Can't fix it so remove the warning light so you can't see it?

NeilM1 said:

So a trip round a few garages ..
2 quotes to remove the warning lights permanently from the dashboard.

Is this the latest? Can't fix it so remove the warning light so you can't see it?

Click to expand...

Possible.. yes

Likely to be legal : MOT worthy .. NO

NeilM1 said:

Is this the latest? Can't fix it so remove the warning light so you can't see it?

Click to expand...

IIRC someone bought a used 500 recently and soon discovered the previous owner had done precisely this.

They ended up having to replace the entire display, and also had to rectify the original fault.

I'd advise anyone buying a used 500 to check that all the warning lights function correctly before purchase. Most should illuminate briefly when the ignition is switched on; as has been said, this is now also checked as part of the MOT. The car will fail the test if any of the critical lights don't function correctly, especially those for the braking and airbag systems. MOT testing stations have comprehensive information about exactly what is supposed to happen for the various different marques and models.

To condense into as few words as possible, don't ever do this.

SOLVED: Start / Stop 1.2 Lounge 2011

Problem solved.

Original error codes :
U1734
Battery Sensor (IBS)
No node on B-Can

B1047
LIN Serial Line

After reading the LIN specification, building a LIN reader and generally getting annoyed with Fiat I solved the problem with an Alfa wiring diagram.

Had Fiat been bothered to update the handbook, or even allowed the viewing of the Start Stop wiring it would have been much easier.

So the first test I did was to test that the IBS had power - it did, that's where my mistake was. LIN Bus runs at 12V, so BOTH wires needed to read 12V, at least at startup.

Second mistake, believing the wire with no voltage was the LIN Bus, it had a little nick in it - should have rang an alarm in head there!

So turns out the RED/green wire is a +ve supply to the IBS, the LIN Bus wire is the other one, which reads 12V, because that's what LIN Bus runs at. I won't going the specs, but think digital +1v on LIN is 0 and +12V is 1, but its not that simple!

Alfa wiring diagrams have an extra fuse - Fuse 87, no mention anywhere in Fiat, but hey why don't I go look, yep Fiats do have a 5A F87 fuse, you can guess what that does and what state it was in. Replaced done, cleared fault, didn't come back.

So, too many Jackanory's from garages and sharp intakes of breath were heard during all of this, so;

The LIN Bus is NOT the CAN bus.
The LIN Bus does not detect bulb failure.
A CAN bus reader probably won't also diagnose a fault on the LIN Bus, unless it has a LIN Bus input.
The LIN Bus is NOT in the diagnostic socket, you will need to manually connect in to one of them (there maybe more than one network in a car), assuming your reader can do it (most can't). TBH I wouldn't bother, read on
LIN Bus errors can be read from BCU, as that's likely to be the Master (not on all cars but is on 500) on the LIN network, errors from LIN Bus slave or lack of expected slave, will be recorded on the Master, they show up in diagnostics.
If you have a LIN Bus error and by chance at the same time a sensor error, which is on the LIN Bus, 99% sure that's where the fault is.
Test the LIN Bus wire for >1V, but likely at startup nearer 12V, it depends on number of slaves on bus. If OK - not a computer error, or LIN wire.
If 3 wires, test GND is OK (IBS has 2 - it's on the GND terminal)
Test the other for battery +, some are hot always, but not all, so try with and without ignition on. No voltage - look for fuse.
The LIN Bus is used for slow TX, so you won't find it on ABS circuits and the like, but door locks maybe, IBS yes, even my Merc has LIN on there!

Hope this will help someone in the future.

Thanks,

Neil.

Well ... it is the future... and your post has helped me! I got the same two errors, and resolved them (so far) by clearing the codes. TBH the battery had gone low and the car had had a small bump, so the codes may or may not return, but I'll know what to work in if they do.