Changed Cat and now have downstream lean and upstream rich condition.

I changed the cat in my peugeot 206 for a new one because it was rusted out. No I have a lean condition downstream that causes the engine to run rich upstream. (downstream O2 is new). Coul this be because I bought a cat that has a newer more rigorous environmental spec? With the throttle on live data says improbable value for both but doesnt throw any codes.

(Edit) Could it just be that a drive cycle has not been completed since clearing of codes? (Wrong place)(/edit)

Did you bought new O2 sensors or swap the old ones?

Although not likely, anything is possible. To give you any diagnosis more data is needed. What year is your Peugeot and what engine. When you have opposite 02 conditions it's a good chance either the upstream or downstream is lying. Viewing 02 voltages in a graphing mode gives good indications of what's happening. You mentioned clearing codes. What codes? What are the 02 percentages? + or - 10% is within normal range for the upstream. Downstream voltage should be around 700mv constant at idle.

2 injectors are constantly on according to live data (120-190% duty cycle) I ordered new ones as i suspect those need to be operational to do a proper diagnosis. There is a no communication code on the worst one and live data is just a straight graph on cylinder 2/3. Injector orings are probably gone on one or more to and I guess that could cause the lean downstream condition since by then the excess fuel migh have hade time to burn off. It's a 2002 peugeot 206 1,4 16v MPI. under 100000 miles

My data is in swedish so Is uspect maybe it's kind of useless to you. Injectors are a common issue on this model aparently but I don't want to get into that until I havreplacements since cheecking them will only make the seals worse.

upstream is ,62 volts and downstream is 1,87(RCO) upstream 28 (RCO) downstream 31 if that helps. It's an autel MAXIAP 200 scanner. Upstream sensor is the original one downstream is brand new and the same part number as the old one.

Code P0203 Injector control malfunction cylinder 3. Also a random misfire code one or more cylinders this morning after leaving the battery disconnected over night. The ignition is fine so it has to be fuel/mix related misfires.

Here are some dianostic sheets from another tool. If my computer had allowed me to attatch files. Maybe my browser is incompatibe,

Delphi/ Autocom data.

P0203 - Injector Circuit Malfunction - Cylinder 3
P0300 - Random / multiple cylinder misfire detected
P1336 - Misfiring

The o2 mv readings on this scanner are close to eachother but between 100-200mv at idle the sensors are definitely responsive to.

Have you tested injectors 2&3 for power and ground. Throwing parts at the problem may not correct the problem. You may have a wiring issue or a bad injector driver in the pcm.
02 mv readings should be oscillating 100-900mv on upstream and steady 700mv on downstream. I would resolve the injector problem first.

Its a pretty involved process on this car to test. I will do though but I'm kind of injured right no so can't disconnect the fuelpump it doesnt have any fuses or relays that I can be totally sure will disable it. The injectors were cheap enough and good to have spares of in any case.

The connectors for the injectors are under the 4 in 1 coilpack and the fuel rail, kind of difficult to get to and seems like there isnt any wiring that can be eaten by mice or such which is otherwise common in my parking lot. (Neighbour had it happen on 2 cars). Right hand kind of mashed at the moment so I'll do that job when it's a little better.

Did some more checks and it seems the IAT sensor is a dud as well so theres another possible contributing cause. Strange that a none value doesnt trigger a code though.