Hi .Guys, set off for work this morning,got down the road and the orange oebdlight came on and won't go off,given the engine runs fine and revs freeley with no limiting I am assuming this is some sort of problem with the oxygen sensor on the cat, could you point me in the right direction ? I have a Tektronix real time digital storage scope and Various multimeters I just need to know how to determine if the sensor is duff or the cat itself is shot.its a 1.2 petrol 2003 doblo with 45,000 miles on the clock from new ,many thanks in advance.

probably best to post in TECH section.. or SEARCH the forum in "advanced..,"
a bit too technical for me..,
a basic code scanner could give you a clue..
or just disconnect battery NEG . lead overnight, and see if it clears..
charlie

Hi, Charlie many thanks for the reply,A wiring diagram could help and as I am relatively new to the fiat forum is there any here I could download ?

Right I have dug out my Haynes manual for mk 1 punto which uses a similar set up and I see how the oxygen sensor works,2 wires from a 12 volt relay to heat the thing up and 2 screened wires to the ECU which must be carrying a low almpitude signal probley square wave that will either change in frequency or almpitude depending what's in the exhaust gases, so it could be anything from a 12 v supply missing as it's fused to just a bad high resistance connection in the sensor plug.socket, I need to have a look in the daylight tomorrow but as you say I will try disconnecting the battery first just in case it only needs a reset .

O.K so I have sorted the problem, when I looked underneath the oxygen sensor was seen to be loose, so loose I unscrewed it just by hand, a few yards down the road from my unit is a subaru garage and we do odd bits for each other so I took the sensor down to them to see if I could borrow a special socket with a cut out down the side to screw the sensor back in and he said where is the crush washer ? so this is why the sensor was loose, the crush washer had rotted away and disintegrated ,however despite my vans instruction book saying the EODB light would go out when any fault had been cleared it did not but the garage extinguished it for me with a plug in scanner, which also confirmed the light had been activated the the oxygen sensor.