Hi,
We have owned a Fiat Sidici 1.6 for about 2 years, after owning it for approx 6 months the engine warning light came on.
I took it to a local garage and they said it was P0420. They told me it was to do with the CAT, but could also be the lambda sensors. They cleared the code and the light went out

After a week or two the light returns, I have bought a code reader and can reset the code myself now. There appears to be no performance issues that I can tell.

I took it to a Fiat dealership recently and they said a new sensor was required and a "software" upgrade. They wanted to charge £300 for this work. I am a little reluctant to do this. I guess I could change the sensor(cheaper), but I am not sure without the software upgrade would the problem be resolved.

I took it for an MOT having reset the engine management light.
It has passed and the tester said that the fast idle test initially failed on the CO reading Actual 0.28% against a limit of =< 0.2%
Second reading was 0.08% so they passed it

Any advice if I can do some tests etc to identify the root cause?

Hi, and welcome to FF,
you'll get a more informed response posting in the TECH section,
quoting the MAF serial number of your vehicles ECU ,( as most won't be familiar with the Sedici's set-up,)

to make life easier - MES will should all of this stuff,

Charlie - Oxford

Hello there my engine light is on I tried to clear it and it won't go off its a sedici 06 any help would be helpful rich

automisprime said:

Hello there my engine light is on I tried to clear it and it won't go off its a sedici 06 any help would be helpful rich

Click to expand...

what code(s) showing,
what description alongside the code..??

a lot of FIAT codes are common to models / engine types.. so use the FF search to read posts for the same codes,

unfortunately the Sedici section is VERY quiet..

Charlie

Thankyou for responding