Hey Fiat 500 Members
I have been advised to repost this in the 500 section from the technical section.

I have a 2010 500 1.2 Pop and it cuts out randomly after 5 - 45 minutes and wont restart immediately. There are No Errors present in the system.

There is no spark and no injection (duration time) when it happens but plenty of fuel pressure.

So Far;
New crank sensor
New cam sensor
Coil pack tried
new engine ground cable
battery ground cable checked
power to coil pack ok
power to injectors ok
two keys tried with the same results
no warning lights on dash
continuity to all sensors from ECU checked and ok
Antenna ring resistance ok

I think the the fault could lie with an immobilizer / body computer / engine computer issue but I am surprised that there are No Errors even when the fault is present and not starting.

FYI I have the Think Diag diagnostic tool?

Any ideas? Any pointers to look out for?

Any help appreciated

Many thanks in advance

Simon

Hi Simon.

Is this isuue an overnight development.. or been creeping in for a while?

Does the Keycode symbol on the dash behave normally..?

Nearest Ive had was bad relay

Have you tried removing the fuel cap see if it starts then?

Most generic fault readers will only read simple stuff. Most manufacturers only paid lipp service to the OBD standard, providing only the basic communication as required by the standard, and putting everything else accessible only with dedicated readers. Fiat is one of the worst in this respect, so needs the dealer diag tool, or MultiECUscan (MES). This needs the program download, onto a Windows PC, a connector and a set of cables. €50 for the licenced version, plus £30 (I think) for the cables. (Might be a bit more)
That will then read the car properly, and all inputs and sensors can be interrogated when the non-start occurs.

There may be someone local to you with MES, if we knew where you were, but this may need attendance when the problem occurs, unles you can reliably replicate it, so having your own may be the way to go. There's a thread where some MES owners have registered their willingness to help, look here: https://www.fiatforum.com/multiecuscan-members-register/

If it starts ok when cold, but then goes dead when hot, something is getting hot and failing. First culprit would be the crank sensor, but you've tried this, so like another, I'm thinking relay. When it stops, does the fuel pump run as ign turned on, and again when cranking?
Other thoughts.
Connector to engine ECU, check connections for evidence of burning.
Fuel pump relay, or pump itself failing when hot.
Ignition switch getting hot?

RalphM said:

Have you tried removing the fuel cap see if it starts then?

Click to expand...

With full rail pressure showing I dont think that would do much.

I am however thinking back to the 188 puntos endearing feature of the board on the ECU that drove spark generation getting hot enough to eventually fail

AFAIK that was a 'hidden fault' no specific errors given or stored.

So IF an Immob. Light WAS showing that might not be related.

Awaiting more info from O.P.

If the immobilizer fails with the engine running it usually fails safe as
you would be pretty peed off if it turned it off in the fast lane of the M6,
Though It likely is something electrical or a connection getting hot and braking down.

Many Thanks for all of the comments and insight;

No there is no Immobiliser light flashing
No MIL light on
and no errors recorded using the Think Diag software that is better than an OBD scanner but I guess is not as thorough as the Fiat device
Yes I have tried the fuel cap removal the first time it broke down on me
I have already reached out to a local member (North Tyneside) with a Multiscan and I am awaiting a reply.

The back story is that this car belonged to a friend of my wife whos father is dying from cancer she is at her wits end. The 500 broke down and was towed to a garage and after two weeks they called to say they couldn't fix it and to come and take it away. She was borrowing cars and eventually hired a car and it was all extra stress she didn't need so I / We bought it from her so it would be one less thing she had to worry about. She now has a replacement car.

Also my wife has always wanted a 500 so it all worked out great for them and now I am selling her TTS while trying to get this fixed.

If I have any updates or the fix I will post

So I dont know when it first happened and how but with 40k+ I guess something has given up for some reason.

I have found a wiring diagram for the engine ECU / body computer antenna / so will be doing some connector checks and continuity tests next week.

Portland Bill
Thanks for the specifics.

Fuel pump running ok and pressure good at the rail
12v at the coil pack and injectors but no signal ground to get them working
Cranking registers on the rev counter and within the live data stream
I did replace the fuse regardless but thus far have not seen any evidence of burning or charring on any of the connectors.
I dont know about the ignition switch but will monitor during the next test, if it starts...

I to have been in the motor trade for 36 years, more lately as a manager, but must admit I am thoroughly enjoying the challenge! I am also detailing it so hopefully by tomorrow night I will start applying the ceramic coatings so that they can be cured by the time its fixed, well that's the plan.....

Check the earth wire for the engine ECU.

All looks to be functional, but just not functioning. Suggests either the ECU is not switching the ign/injectors, or it is, but there's no ground path. I think it earths onto the cam cover or somewher nearby, but not sure. Even it if looks good, worth removing, cleaning and refitting.

Stilo, I think, had an issue with dry solder joints inside the ECU, and the fix was to cook it in the oven. This reflows the solder apparently. Sounds scary, but somewhere there are threads from successful people.

MIL light will only come on if a sensor gives a reading outside expected parameters. I don't think the ECU understands if its instructions are not working, so it might be switching an earth, but does not measure its success, so no MIL.

Thanks Bill,
The ecu earth is indeed on top of the rocker cover (showing my age there) cam cover and is zero resistance to the battery ground and even a direct bridge didn't make a difference.

Does an oven get hot enough to melt solder?

I have traced the soldered joints within the harness a resoldered them just in case but internally to the ecu? Thats a new one for me.....

I will research this a an option

The quest continues.....

Have a read of this thread. https://www.fiatforum.com/stilo/445511-ecu-oven-method-re-flow-worn-solders.html

Thanks Bill,
I will consider this as an option only perhaps as a last resort. And if I can persuade the missus to let me do it!

Cheers

Simon

Tricolare said:

Thanks Bill,
I will consider this as an option only perhaps as a last resort. And if I can persuade the missus to let me do it!

Cheers

Simon

Click to expand...

A significant part of the thread talks about whiskers on the solder. A good look over the board with a magnifying glass might reveal some needing careful trimming, avoiding the need to cook it.

Yes I saw that and I have an Android microscope for my phone that I use for paint defects, I will use that and can take photos should I find anything.

I should get back onto the car on Wednesday ish.

Well I had a quick check just now and the car started but shut down after barely a minute.
I left the ignition on and scanned the system with BCM first and Engine second.

The BCM had two errors recorded 'U1701-87 Emc - Engine Control Module Node - Node On C CAN'

and a weird '39,1e,04,ac(p04c)' I have no idea what this means

These both disappeared on their own with an ignition key cycle but the car fails to start

Their were no errors in the Engine ECU

The Quest continues

I’m not a fan but will it start with a spray of easy start? Also if you don’t fancy cooking the engine ecu in the oven try using a heat gun directly on the PCB if you can? I have never tried it on a car but has worked in the past on an old laptop��

I assume the dash lights up as it should and it turns over just fine but dosnt start?

Hey Chris,
Yes dash OK no lingering warning lights and spins over. No spark and no injection.

Today was spent confirming wiring continuity on the CAN line from body comp through the ABS to the engine ecu.

Still no real errors but the data stream shows zero injection duration and also the immobilizer key not recognised. Maybe coz the body computer was completely disconnected.

I don't have the code card and the idiot at the local dealer wants £54.47 to supply it to me.

Thats tomorrows problem...

Tricolare said:

Hey Chris,
Yes dash OK no lingering warning lights and spins over.

I don't have the code card and the idiot at the local dealer wants £54.47 to supply it to me.

Thats tomorrows problem...

Click to expand...

Apparently there is no fixed fee..

£20/£25 sounds a more common charge for an A4 printout

I expected £20 but how can there be a £55 charge for something the supplying dealer should have on record?

Can I go to Fiat UK direct?