I'm looking for some advice.
I have a 2008 fiat 500 1.2. Around 2-3 weeks ago it came up with an EML took it to a garage and long story short they said they couldn't diagnose it but gave the code P1220.

I'm a student and couldn't afford to take it to fiat and my OH is a newly qualified mechanic who has just started working in a proper garage, he plugged his diagnostic machine in and found the P1220 code and the cars TP is reading at 87+, did some research and plugged his own 2008 500 in to compare and recommended I changed the throttle body.
So I did yesterday.
Plugged it in again today and it's still reading the same code, the TP is still reading at 87+ as well as the oxygen sensor (apologies I think it's called that) giving off a strange pattern whilst the car freaks out on idle.

All in all I'm disappointed I spent out on a new throttle body and it not solving the problem and he's disappointed that he hasn't solved it first try.

Can anyone please shed some light on the potential problem and a resolution before I have to resort to using my entire student loan to take it to fiat.
Thanks in advance,
Caitlin

I can't help much but can add if the code relates to the O2 sensor being faulty that should have been replaced first I'm sure someone more knowledgeable will be here soon and welcome. A duff O2 sensor will give all sorts of running issues especially at idle always buy a quality OEM equivalent sensor never a cheap or universal one, any garage used will require Fiat specific diagnostic software too.
https://www.shop4parts.co.uk/?name=store&op=Details&ProdID=13900&sku=254201

I had this code. There’s a thread on in somewhere. I changed the throttle body and the throttle pedal but every time I reset the code and drove it, it came back straight away. Ended up being the ECU. Bought a second hand ECU which then had to be virginised.

Often faults flag up codes further down the line from the actual problem.

It's a knock on effect, it could be an input related to the TB is having an issue and the ECU detects the TPS signal (and various other sensors like the MAP) just don't add up, it doesn't know why, so if flags up the part struggling to cope as it's being asked to work outside its parameters.

Quite often these sort of "knock on" faults result from problems with sensors or inputs that can't really register their own faults properly as it's circuit isn't completely broken, it's just missing part of it.

A pedal postion sensor is one likely culprit.
It's a style of input sensor that can wear and fail to send a part signal but it's only real way of flagging it's own fault is a complete circuit break.

It's more often than not false economy replacing parts in hope just on a fault code alone, what's needed is an actual confirmation that it is the actual problem and some diagnosis skills are required for that.

It can be mostly done via a scan tool, logging sensor signals in various positions, but you really need to know what to look for from them.

As a rough guide, sensors are usually fed with a set voltage to alter which is 5v, then sends a signal back the ECU usually return between 0.1v and 5v depending on what it's doing/position.

You might be better looking for diagnostic service, there are a few mobile ones about that don't charge to much due to low overheads, they should be able to whip through it fairly quickly and will know what to look for.
It should save you some time, effort and money in the long run.

I completely realise Caitlinhannah18 needs to save money and she also needs to get the problem fixed, but dare I say it, this is often one of those cases where it might be cheaper from the start to take the car directly to Fiat for diagnosis. I've done it myself and learned the hard way, spending months trying to diagnose a misfire until I finally bit the bullet and had the car properly diagnosed at a dealership to discover I had a faulty fuel injector. If I just gone there to start with, I'd have been over £200 better off in my pocket and I quite literally wouldn't have wasted multiple hours trying to sort the problem out myself. I agree, dealership diagnostics aren't particulary cheap, but I guess it all depends on how much pain you want to put yourself through just to save a few quid.

Just re read the OP.
You have access to two 500's with the same engine, try swapping the throttle pedals assemblies over.

That should discount or confirm that component.

Another suspect could be the temp sensor, air and fueling strategies are dependent on engine temp.

Did you change the TB for a new one?

Goudrons said:

Just re read the OP.
You have access to two 500's with the same engine, try swapping the throttle pedals assemblies over.

That should discount or confirm that component.

Another suspect could be the temp sensor, air and fueling strategies are dependent on engine temp.

Did you change the TB for a new one?

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We'll have a look at that tonight. Yes changed the TB for a new one

My fault in the ECU was eventually tracked as the ECU had two feeds to the sensor, one was 5 ohm and the other as 8.

Caitlinhannah18 said:

We'll have a look at that tonight. Yes changed the TB for a new one

Click to expand...

Proper Fiat specific diagnostic software like Multiecuscan (MES) www.multiecuscan.net would help with fault finding. Where are you located? There mybe someone local to you with MES, I'm near Cambridge.

Robert G8RPI.

Just been having recurring check engine etc problems on ours that came and went so bought a reader and had this P1220 fault which I cleared.


But it went into Fiat anyway as under warranty still and they couldn't find the fault on their diagnostics but changed the throttle pedal based on that code I gave them - will report back if it comes back.