I'll give a bit of history first of all

Bought the car (57 reg) in Feb/March 2015, first viewing took it a drive couple of minor problems, one of which being the EML is on, no biggie dealer will reset, picked the car up a week later EML still on & dealer reset in front of me

Code P0133 Heated oxygen sensor (HO2S) 1, bank 1 -slow response

Fast forward a couple of months and its back on, same P0133, reset myself and on my way. Couple of months later its back on again P0133, this time I've changed the o2 sensor for a Bosch part (OE equivalent) all is fine & dandy

Again a couple of months later its on again, guess what code? so this time I've changed to a genuine Fiat part & by now its MoT time, Failed it on emissions, fuel treatment & spirited drive gets it through

Next up is a remap by Angel Tuning Scotland, mapped ok however Paul feels its down on power, but still, running good for over a year and with new clutch & timing belt/water pump and a battery gets me up to this point

Driving up the A1, filled up with Tesco Momentum 99ron, doing around 60mph, EML flags up again, got the code reader out back home and yep P0133, again :bang:

Now bar a small hole (like, very small) in the down/middle pipe there are no noticable exhaust leaks pre-cat or anything else I can think of to cause it

Anything else worth checking before chucking a new sensor in?

No one?

Sorry I don't have a direct answer!

Maybe reading the fault codes with MES may give more information on the fault? Or depending on your locality to an independent specialist like alfa workshop or autolusso who both have use of official fiat software and experience with the Tjet engine maybe be able to offer a solution.

I would say it's not your o2 sensor at fault as you've changed this.

Alternatively you could search alfaowner as the mito used the same Tjet 150 unit or abarth forum to see if you can find anymore information.

If you find a solution please let us know.

Not much on Alfaowner, infact not much anywhere other than change the sensor, but nothing to say what could be causing it

Have an Alfa specialist near me so may dive in during the week & pick their brains a little

Use MES, clear codes.
Graph O2 sensor response /voltage.

Even if it looks like what the code says. It can still be a bad/ oxidized connection.

Cleared the codes & fitted new sensor, old one was hanging around 0.400v - 0.475v, new one is at 0.700v - 0.350v

Pretty sure this is only curing a symptom though, not the cause

Fix that hole!

Is it using any coolant? Antifreeze will kill O2 sensors if there is a small leak in head gasket.

wad2502 said:

Is it using any coolant? Antifreeze will kill O2 sensors if there is a small leak in head gasket.

Click to expand...

Funnily enough, service history shows the HG as being changed a few months before I bought the car, though it hasn't lost any coolant or had any other problems

Do u have multiscan and connectors? That should give a good indication as to what is going on. Look at voltage range on O2 sensor and also check its not running lean due to partially blocked injectors. Have you run any injector cleaner through it?
Running lean might be a result of airmass meter issues too Mulitscan can help there also.

Ok so had a look with ECUScan and here's what I'm getting, not sure if its whats expected but oh well, also had another issue this afternoon, filled up about £20 of shell regular and a couple of minutes after leaving the station I started misfiring pretty badly, switching off and on again 'fixed' it but there's nothing stored to say what went wrong