Hi all. This is my first post on any forum but figured this may help some with this fault if having difficulty. This is on a grande punto 1.4 petrol 2006

Before I start be very careful using a multimeter around any airbag wiring!

Went out to vehicle and code b0117 front crash sensor showing. Permanent fault that cannot be erased. Having rang fiat and finding out the cost of a crash sensor and almost dying I decided to carry out some further checks.
Behind the front grill towards left hand side is where the crash sensor is located. To gain access you must remove some torx 30 and gently pull away the plastic piece. The sensor is then held in place with a 10mm bolt. Remove the bolt and lift the sensor and wiring up. I then disconnected the battery. If you look under the fuse box on the nearside there will be two multiplug connectors. The one on the right, the black one is where the wiring goes to from the crash sensor. Disconnected that and the one to the fuse box above it. That is the two connections from the front wiring loom. I also disconnected the crash sensor.
This is where the multimeter comes in so be 100% nothing else is connected to either the fuse box or control units. All that is being tested is the wires. Nothing else connected.
On the wiring the crash sensor wires are coloured black and brown and then the other is red and green. I tested continuity between the multiplug near fuse box and the wiring at the crash sensor. Tested black and brown first. All okay then tested the red and green. No continuity. Started testing wiring moving leads closer from multiplug to crash sensor plug until it had continuity. Eventually it did indicating a broken wire. In my case it was rotten. Just green dust was all the was left. Stripped wiring back and soldered. I used a gas soldering iron not a mains one. Rebuild everything and check codes erased. All went out. Hopefully this help someone. I am new to this forum stuff but don't assume it's a crash sensor as they are not cheap new!!!

I've been "messing about" on a hobby basis, with vehicle diagnostics for about 6 years now, ever since I bought my VAG-COM and a little more than a year ago I bought my MES. The first few successes I had were straight forward in the respect that the program identified a faulty component (sensor, actuator etc) which I replaced and everything worked fine! Great, I thought! This is just so easy! Wish I'd bought my VAG-COM sooner! Then I ran into the first one that didn't "play the game" it wasn't the sensor, it was a corroded plug pin! In fact I could have sorted it by cutting the plugs off and soldering the wires but by then I'd bought a new component (ABS sensor) which included the plug but when I plugged it in it didn't work! It was then that I saw the corrosion on the pin in the other half of the plug which I cleaned up before smearing some Contalube 770 in it and reassembling. I probably didn't need to buy the sensor, although the corrosion was worse in the half of the plug on the sensor wire. (or so I've convinced myself) So now I know that the best the program can do is tell me there's something up with a system and its up to me to then intelligently track it down! Your post above is a perfect example of how easy it would have been to waste a lot of money needlessly, especially where, as in my case, labour costs are not a factor!

Thank you so much for this post - I just love reading about this sort of thing.

Thank you for the positive feedback.
I've worked in the trade long enough to see too many components replaced down to fault codes alone. I've done it myself. Best ones are mass air flow meters. Vauxhall especially on insignia' s with boost pipes split and one garage had replaced the sensor with 3 different sensors!
Thank you for taking the time to read my post and thanks again for your positive feedback

Greenwoodvehicleservices said:

Thank you for the positive feedback.
I've worked in the trade long enough to see too many components replaced down to fault codes alone. I've done it myself. Best ones are mass air flow meters. Vauxhall especially on insignia' s with boost pipes split and one garage had replaced the sensor with 3 different sensors!
Thank you for taking the time to read my post and thanks again for your positive feedback

Click to expand...

You're very welcome sir! You described it so vividly I could almost imagine myself in there with you weilding the tools alongside you!

I'm in my early 70's now and have spent a lot of my life "on the tools" although latterly, since my early 50's I branched off in a different direction but still remained very active servicing and repairing "the family fleet", restoring older horticultural machines and "messing about" with anything mechanical I can get my hands on (restoring, at a leasurely pace, an early 50's NSU Quickly just now). The last vehicle "family" I did official courses on was Montego/Maestro!! So you can see I don't have in depth knowledge of modern electronic systems but did experience the earlier emissions "stuff" and I'm learning as I go with the family vehicles.

I've reached the stage now where I can really see the advantage of having an oscilloscope, oh boy, would I love one of those! A Pico would just be wonderful! Unfortunately I don't think I can afford one just to "play" with though. Always good to have a goal to aspire to in this life I've found - it keeps you going!

Kindest regards
Jock

All test and diagnostic equipment are aids only. Just because the kit indicates a fault one has to ask sensible questions about why would the test kit give the result, even diagnosis, it does. Between the both of you with thought and reasoning on your part and understanding of the tests and equipment involved then good outcomes are to be reliably expected.

I remember on our old Fiat Tempra 1.8ie the engine would detonate at high RPM. Vehicle was still under warranty and I recall the dealer test driving but could not hear the pre-ignition at high RPM. Was listening for the wrong sound. At high RPM pre-ignition/detonation is characterised by "tinkling" sound like small washer being dropped.

I pressed my case so they put the car on the diagnostic kit, revved the nuts of it in testing and deemed the timing to be correct. No fault found!

When I got home I tackled the problem by going back to basics. I found that the TDC sensor had been factory fitted (sheer bolts) 5 degrees advanced. I repositioned the sensor and bingo all was well.

The mistake the garage made was to trust their diagnostic kit. They could see/read the timing and the values were correct at idle and up to the rev limit and took the results on face value.

Off course if the datum reference point, in this case the TDC sensor, is incorrect then the kit will still give accurate measured values with reference to the datum. So instead of 15 degrees advance at 850rpm (as measured) it was actually 20 degrees of advance.

So, get to know your kit, what it is doing/measuring and what factors could be affecting your measurements, etc.

Diagnostic scanners and oscilloscopes are great pieces of kit if the user has the understanding of how to use them and more importantly what the value should be in the first place.
I work as a technician for an independent garage. We do hell of a lot of diagnostics however I spend just as much time printscreening actual values and oscilloscope patterns on good cars as faulty ones.
S130- that's an awesome story. I love it when it's been to dealers who should have more information and knowledge than most others, yet if they just delved a bit deeper than what the machine say it can be an obvious fix.
Puggit auld jock- if your looking at oscilloscopes the picoscope is a very good piece of kit however I must agree it's very pricey. Check out there website on "library" section and there are some patterns of both good and faulty signals.
I use a bosch kts with the fsa oscilloscope and Its massive money. For home use I believe sealey do a oscilloscope for a few hundred pounds iirc. Your actual values on good working cars are a life saver though!

Thanks for that Greenwood. Yup, it's all about "the knowledge" isn't it. I've looked at the Pico site a few times and it's very interesting. I also have an excellent book Automotive Oscilloscopes Waveform Analysis by Graham Stakes which I bought with last year's Christmas book token which my brother gives me every year!

I've looked at the Sealey and Foxwell (Gendan) which look very like the Hantek? Trying to decide if I'm brave enough to go for a Hantek direct import! I have a preference for a PC based system. Whatever I decide it's obviously going to be a very steep learning curve! Luckily our local Audi/VAG specialist married our good friend's daughter and he seems very amenable to giving advice and guidance. I think there is probably novelty value in this "silly old fart" who is still, at 72 years old, crawling around on concrete floors with dirty oily hands! I need to be careful not to become a nuisance though. He has already suggested that storing results when the car is running well, so you can then do a direct comparison when problems are being experienced, is a good idea - especially as I'm mainly working on the "family fleet" so there are not that many vehicles involved.

Kind regards and all the best
Jock.

The final job on the £250 bargain GP Sporting was the airbag light

I read Greenwoodvehicleservices post on faulty crash sensor and one of the previous owners had said it was the front crash sensor, I changed it but it did not self heal.

After reading a lot about faults with modern Fiats and Its foolish to guess, I ordered MES and spent may hours studying how it works (studied many hours on what I needed on the website!)

What a great piece of kit this is I scanned the airbag module and only got error the light was on with code B0117 and no advice on what was wrong
so I followed Greenwoodvehicleservices advice and stripped all the front crash sensor wiring out - big job with lots of parts taken off and yes there was telltale green corrosion on the green and red wire about 25cm from the crash sensor, I wiggled it and it snapped in my hand.
Used a crimp connector with a heat shrink cover to join the wire, temporarily set everything back up, reinstalled the cleaned up fuse box and put battery back on, turned the key and light still on, scanned it and this time I got some help error was intermittent, cleared the code and the light went out yeah!
schoolboy error I left the airflow metre off when I started the engine and an engine warning light came on - bugger!
took the yellow adaptor off and scanned the engine ECU and found a few intermittent codes - dirty fuse box?, cleared them and the engine warning light went out - Result

The old git is learning about modern cars - slowly!

Please be careful working on airbag wiring, if you have to replace any wiring use the correct gauge wire - no exceptions here - I was lucky and just used a crimp connector with heat shrink, its all about resistance etc etc.......
Disconnect the battery, disconnect ALL of the fuse box - clean it all up while its off the car.

Thanks to all the great posts on here and a great blog on SRS written by a GM tech.

Car is sold - next project!!

Ian