Background is that 14000 mile 1.2 500 was serviced and cambelt replaced by local garage and now has issue sometimes with engine light coming on when cruising at approx 2200 rpm (ie 50mph in 5th,but can occur in lower gears also) on slight to no throttle but it continues to run fine.
Took back to garage they found error is miss fire on 2 and 3 but changing coil pack, plugs and leads did not cure so they are baffled and think ECU or wiring fault most likely, car is 6 years old so probably uneconomic to pursue further hence the post !!
Basically car will be sold if nobody knows as SWMBO won't drive it now !
I've been using for work and if trashed light stays off but cruise a few seconds with just the right throttle and light sometimes comes on, could not make it come on friday or all weekend but came on twice on way home tonight (cleared by turning off and on again) so really odd.

Do you know anyone with Multi ECU scan? That may well hold codes if a light is on.

typecastboy said:

Do you know anyone with Multi ECU scan? That may well hold codes if a light is on.

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6 year old and 14k? read codes, head gasket? Lambda?

John202020 said:

6 year old and 14k? read codes, head gasket? Lambda?

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Yeah lambda will certainly show up in MES.

Hi,
If the fault was not there before the service & belt change and was when you picked it up it seems likely to be connected to the work. The grage who did the work need to show that it's not something they have done. I guess the garage does not specialise in Fiats. As others have said you need to get proper, Fiat specific diagnostics run on the car. Multiecuscan is a good option. I assume you meant 140,000 miles not 14,000


Robert G8RPI.

Could go on guessing but really need codes scanning, did it do it before cam belt?

Not a typo 14,000 miles in 6 years !
No problem before service/cambelt so garage was expecting to find a loose plug lead or faulty plug etc as a result of service and like I said are baffled.
I was thinking that the generic code reader may not be giving the real cause and Multiscan may be the only way forward and some of you have confirmed this is possible.
My thought is that the new cambelt has very slightly changed the timing and a sensor is detecting this as I've read somewhere that there is a sensor alignment process that is sometimes required after engine work ?
As I said car drives fine and error only seems to appear if 2200ish rpm is held for 2 or 3 seconds with light/no throttle (as I said first time and most common trigger is going from 30-50 limit in fifth on a flat to slight downhill, you hit 50 back off the throttle and 2 seconds later the light comes on.
Drove to work this morning in 20 and 30 limits no light, but last night light came on at the 50 limit (different route home) and again after restart when stuck behind a very slow driver in a 40 limit (they were doing 20!) when I must have hit the trigger point again in a lower gear.
I've tried thrashing it and driving in too high a gear with throttle wide open to trigger knock sensor but nothing it just ignores me.
If anyone around Sheffield has Multiscan let me know otherwise I'll buy the leads etc and give it a final chance (cheaper than letting dealer fail to find error! ) before SWMBO finds WeBuyAnyCar website

When a cambelt is changed, there may be a slight mismatch between crankshaft and camshaft positions. An alignment process should be carried out, but can only really be done with Fiat specific software, and MES can do this. I think there is also a process where the engine can be revved several times to cause a reset, but you'll have to search the threads to find that. The Fiat procedure does involve revving it but with the computer attached is quicker to make the two sensors agree.

Needs this done before any further diagnosis.

"Phonic wheel relearn" See this thread: https://www.fiatforum.com/panda/355001-engine-light-flashing-after-cambelt-replacment.html

portland_bill said:

When a cambelt is changed, there may be a slight mismatch between crankshaft and camshaft positions. An alignment process should be carried out, but can only really be done with Fiat specific software, and MES can do this. I think there is also a process where the engine can be revved several times to cause a reset, but you'll have to search the threads to find that. The Fiat procedure does involve revving it but with the computer attached is quicker to make the two sensors agree.

Needs this done before any further diagnosis.

"Phonic wheel relearn" See this thread: https://www.fiatforum.com/panda/355001-engine-light-flashing-after-cambelt-replacment.html

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Thanks this confirms my thought that cambelt change is cause and when engine is held at a particular speed for a few seconds the ECU doesn't see what it expects and gives an error, possibly the ign timing is a fraction off for cylinders 2-3 hence the generic reader showing miss fire ?

Whilst I'm not for a moment advocating neglecting changing the cambelt at the recommended interval, it's interesting to note that there have been more posts than I can remember about folks with issues after having one changed. In contrast, whilst we've had a few timing chains snap on high mileage diesels, I don't think there's been a single post about actual cambelt failure on a petrol car.

It's a pity the 1.2 FIRE is no longer a non-interference engine; it's pushed a lot of folks into early cambelt replacement.

jrkitching said:

Whilst I'm not for a moment advocating neglecting changing the cambelt at the recommended interval, it's interesting to note that there have been more posts than I can remember about folks with issues after having one changed. In contrast, whilst we've had a few timing chains snap on high mileage diesels, I don't think there's been a single post about actual cambelt failure on a petrol car.

It's a pity the 1.2 FIRE is no longer a non-interference engine; it's pushed a lot of folks into early cambelt replacement.

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At least its not a Ducati,2 belts with 2 year change regardless of mileage and they do let go if you push your luck !
Regardless of the engine carnage that would result the idea of a belt failure mid overtake etc is probably worth the cost/ hassle by itself as I wouldn't want to be the one find the limit as you just know it wouldn't fail anywhere safe

Is it possible the cam is one tooth out? I had Fiat do the belt as they were the cheapest! It's a fixed price item they said

The process requires the cam gear bolt to be slackened, then the belt tensioned, and the gear bolt torqued up. This is done with the cam held in place with a special tool, as is the crank. This allows the cam gear to be correctly placed with the new belt, so timing is accurate. Then the phonic relearn is carried out and all should be fine.

When I did mine, the engine is started to carry out the phonic relearn, and of course at that time the engine light is on. With the computer plugged in, a phonic relearn is done, after which the light extinguishes as it is all happy again. All explained in the Haynes manual. Any garage that subscribes to data, such as that provided by some cambelt manufacturers, or other data suppliers, should have this info to hand. But, such subscriptions are expensive, and difficult to justify if such work is infrequent.

Buy a Haynes, then either find someone local with MES, or buy the registered version and sort the phonic relearn. MES will also reset the service interval counter is yours has one.

Phonic Relearn appears to have fixed the issue.

Thanks for the info. I have managed to sort this issue 'multiple misfire' with a phonic relearn 3 x 5000rpm revs and all seems well. this was done without computer.

pasotibbs said:

At least its not a Ducati,2 belts with 2 year change regardless of mileage and they do let go if you push your luck !
Regardless of the engine carnage that would result the idea of a belt failure mid overtake etc is probably worth the cost/ hassle by itself as I wouldn't want to be the one find the limit as you just know it wouldn't fail anywhere safe

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The 1747cc used in the Punto HGT and the Alfa TS engines are all 40K or four years. Exceed that and you are looking at (on top of the head repairs) at least removing the engine for checking/replacing crank bearing shells and at worst replacing the lump.
Renault say theirs will go for 70K but the small print says if it's mostly doing short journeys the belt is down-rated to 40K.

This 500 with such a short mileage (regardless of age) deffo needed a new cam belt.

Here's a youtube guy carrying out the process