Technical Punto evo airbag light on.

[Michael Dranfield]

Hi guys,the Airbag light came on on my wife's punto evo last week and a message on the dashboard flashes up airbag failure,I took it to my friends garage,he does not specialise in fiat but ran a diagnosis scan and the code says airbag power supply failure,which he suggested may be a blown fuse,with this in mind I remember fiat troubles with chaffed wires in the rear hatch ,I pulled back the rubber boot and sure enough two high current wires and a thin black wire had bare wire showing,I assume the two thick black wires are for the heated rear screen,it it possible this may be something to do with the airbag failure ?? My friend has identified a fuse I need to check but not got round to it yet,got to get it sorted soon though as the mot is in a couple of weeks.

 

[varesecrazy]

Quiet on here..

May well be same in the GP

 

[Michael Dranfield]

I wasn't building my hopes up as the air bag electronic systems all seem to be some closely guarded secret .

 

[Michael Dranfield]

Ok so need some real help now from a electronic diagnostic expert,my friend identified A fuse I need to check under the dashboard in the glove box,when I opened the glove box I noticed the light did not come on ,so I pulled the fuse he said could be the air bag control power supply but it tested ok,however as soon as I put it back in the glovebox light came back on,so I was very excited thinking the air bag control must share the same common power supply ,now the Haynes manual says any airbag codes are not self resetting and must be reset with a scanner so I borrowed my friends snap-on ethos+ scanner but as soon as I reset the airbag code it comes back on again,the code displaying is B0101 Airbag control unit power supply ,can any one help as the Mot is looming , many thanks in advance.

 

[Michael Dranfield]

Ok so we don't have any electronic diagnostic members here,can any one recommend​ a place that could test me the air bag ecu ?
I have played around with my friends scanner and I have concluded it's most probley bad data in the airbag ecu , corruption more than likely caused by the fact the battery's getting a bit tired and I should have changed it long ago !!
The live data on the scanner reports several systems not responding,both front impact sensors absent seat belt fastened absent ,seat occupancy sensors not responding,as a test I took the car for a 30 mph blast down the road with no seatbelts on and a front seat passenger and no alarms go off, so this seems to indicate the scanner is correct,however all the air bags are responding apart from driver side stage two so I don't think the ECU has lost its power source at all.

 

[varesecrazy]

Ok so we don't have any electronic diagnostic members here,can any one recommend​ a place that could test me the air bag ecu ?
I have played around with my friends scanner and I have concluded it's most probley bad data in the airbag ecu , corruption more than likely caused by the fact the battery's getting a bit tired and I should have changed it long ago !!
The live data on the scanner reports several systems not responding,both front impact sensors absent seat belt fastened absent ,seat occupancy sensors not responding,as a test I took the car for a 30 mph blast down the road with no seatbelts on and a front seat passenger and no alarms go off, so this seems to indicate the scanner is correct,however all the air bags are responding apart from driver side stage two so I don't think the ECU has lost its power source at all.

Hi. You are far better qualified than me..

But we have a few who tend to post informative info.

g8rpi
Being a prime example

Unfortunately the evo and 2012 sections are mega quiet..

Charlie

 

[g8rpi]

Ok so need some real help now from a electronic diagnostic expert,my friend identified A fuse I need to check under the dashboard in the glove box,when I opened the glove box I noticed the light did not come on ,so I pulled the fuse he said could be the air bag control power supply but it tested ok,however as soon as I put it back in the glovebox light came back on,so I was very excited thinking the air bag control must share the same common power supply ,now the Haynes manual says any airbag codes are not self resetting and must be reset with a scanner so I borrowed my friends snap-on ethos+ scanner but as soon as I reset the airbag code it comes back on again,the code displaying is B0101 Airbag control unit power supply ,can any one help as the Mot is looming , many thanks in advance.

Hi,
I did not see your original post, not Punto owner so omly pick up what shows in "new posts"
This needs some basic fault finding. First thing is to ensure all supplies and grounds are present at the Airbag ECU. It's not unusual for airbag ECUs to have multiple supplies for redundancy. To check the supplies you need the wiring diagrams (schematics) from eLearn or autodata. Don't seem to have much in the downloads section for the EVO. I' like to help but am pretty far away from you (Cambridgeshire) . It's hard to do much remotely, and it depends on your skill level. Do you have a multimeter and how confident are you using it?


Robert G8RPI.

 

[Michael Dranfield]

Got a £650 fluke DMM and Real time digital storage scope but not a lot of use without a circuit diagram,nothing relating to airbag ecu in the Haynes manual,I have just had a look on the net and it looks like the serial eeprom may be corrupted and just needs reprogramming but I can't find a bin file either.

 

[g8rpi]

Got a £650 fluke DMM and Real time digital storage scope but not a lot of use without a circuit diagram,nothing relating to airbag ecu in the Haynes manual,I have just had a look on the net and it looks like the serial eeprom may be corrupted and just needs reprogramming but I can't find a bin file either.

Hi,
Basics first. From a quick look I could not find a copy of eLearn for the evo on ebay but thre is one for the GP https://www.ebay.co.uk/itm/FIAT-GRA...ND-SERVICE-MANUAL-1-DAY-DELIVERY/132180872193
You might find an evo one on ebay.it A GP diagram would at least give pin connections. but cheeck what airbags fitted Should be Continental but some have TRW. Multiecuscan www.multiecuscan.net and an el inteface + adaptors would be a good investment too.


Robert G8RPI.

 

[Michael Dranfield]

Snap on scanner says contenental ECU is fitted but unfortunately I think we're stuffed with this one Robert,I contacted a couple of people who say they can repair airbag systems but when I told them it was a punto evo they both said the same thing,this type can't be repaired and it is also coded to the vin number of the chassis so no point in even buying a second hand one,and with the mot been only 6 days away looks like I will have to take out a second mortgage and go to a fiat main dealer,but thanks for your help anyway.

 

[varesecrazy]

A decent fiat:alfa indy should have access to the same kit..

And potentially better versed in its use. Charlie

 

[Michael Dranfield]

Problem is the mot is due in 6 days time and the last thing I need is main dealer picking up on this and saying you need to let us do the mot or you can't drive it away because I know it also needs 4 new tyres which I can get for £50 each.Going to try the two nearest main dealers in the morning and see if they will tell me over the phone how much they will charge to have a look and give an estimate for repairs .

 

[g8rpi]

Snap on scanner says contenental ECU is fitted but unfortunately I think we're stuffed with this one Robert,I contacted a couple of people who say they can repair airbag systems but when I told them it was a punto evo they both said the same thing,this type can't be repaired and it is also coded to the vin number of the chassis so no point in even buying a second hand one,and with the mot been only 6 days away looks like I will have to take out a second mortgage and go to a fiat main dealer,but thanks for your help anyway.

Well a main dealer will just change the ECU and you will have to pay even if it's not faulty. The eLearn linked to is only £7 and electronic delivery. I'd still want to check power and grounds before buying an ECU.

 

[Michael Dranfield]

Well rang the main stealerhip today,£89.99 to tell me what I already know,however this prompted me to have another look tonight but the more I look the more nothing makes any sense so I wonder how if it is only needs a software update ???
Scanner shows multiple errors ,taking just one as an example it says the front seat belt stalks are working o.k ,however the car thinks otherwise,when I turn the ignition key after a few seconds the seat belt locked light goes out even though the seat belts are not clipped in at all .I have checked both stalks and the microswitches do toggle between zero ohms and infinity when the seat belts are clipped in or out so clearly the snap on scanner is right but the car is wrong.

 

[Michael Dranfield]

Well a main dealer will just change the ECU and you will have to pay even if it's not faulty. The eLearn linked to is only £7 and electronic delivery. I'd still want to check power and grounds before buying an ECU.

Many thanks Robert but I don't think e learn for the grand punto will help with the evo because I have a Grande punto as well and I have made some comparison checks between the two cars ,on the Grande the seatbelt stalks micro switch are normally open but on the evo they are normally closed.

 

[Michael Dranfield]

Another perculiarity I see ,on the evo there are 2 sets of wires under the seat 2 for the seat belt stalks which operate ok ,so that leaves the other loom a of 3 wires,now given the evo has airbags in the seat side I can only see one possible configuration for the 3 wires and that is seat occupancy sensor switch and air bag trigger with a common ground or earth, however when I meter the 3 wires one pair is short circuit, zero ohms no matter if the seat is occupied or not and the other pair measures infinity, now logic would tell me the seat occupancy sensor is stuck down but the passenger seat gives the same reading so it seems a bit unlikely both seats are faulty, I can't make any comparisons with the Grande punto as there are only 2 wires due to no seat airbag.

 

[g8rpi]

Many thanks Robert but I don't think e learn for the grand punto will help with the evo because I have a Grande punto as well and I have made some comparison checks between the two cars ,on the Grande the seatbelt stalks micro switch are normally open but on the evo they are normally closed.

Does the GP have the Continental airbag system? The GP has two different systems and eLearn covers both. If it's the same series ECU I doubt the power pins have changed.


Robert G8RPI.

 

[Michael Dranfield]

I don't know as I have taken the scanner back now but I can't get out of my head with 3 wires to the seat how can 2 be zero ohms no matter what you do ? And both seats read the same,surley both seats could not have gone faulty at the same time ????

 

[Michael Dranfield]

ok so just had a look on the internet while eating my dinner researching what part the front seats play in the airbag system and it would seem I have solved the mystery of the short zero ohm reading on the seat connector ,a special type of plug and socket is used with a built in shorting bar which as soon as the plug is detached from its socket puts a dead short across the airbag trigger wires so when the airbag is removed there is no danger of it been accidentally fired by a charge of static electricity.
As for the seat occupancy sensors having an infinite resistance reading the snap on scanner said both seats are working so it could use a capacitive pressure sensor rather than a restive one and in this way the system can determine how the occupants are placed in the seats.
All clever stuff but unfortunately my new found knowledge on SRS systems is all immaterial now as the car is booked in the mainstealership tomorrow for evaluation but my conclusion is one of two things either it needs a software upgrade or the airbag ecu is faulty.

 

[varesecrazy]

ok so just had a look on the internet while eating my dinner researching what part the front seats play in the airbag
All clever stuff but unfortunately my new found knowledge on SRS systems is all immaterial now as the car is booked in the mainstealership tomorrow for evaluation but my conclusion is one of two things either it needs a software upgrade or the airbag ecu is faulty.

Well.. what did they discover?