Following up from my post "antipollution fault" showing up on my wifes 1600cc petrol C4 Citroen, a code reader suggests it's an ignition fault, this seemed probable due to it having an intermittent misfire when the fault light came on. I fitted a new coil pack and plugs and had the fault light switched off. Within 5 mles the warning light and read out "antipollution fault" came on. I have had a look at the wiring etc and all seems secure enough and it starts and drives well apart from the irritating read out beep and warning Iight. Any suggestions or do I just live with it, being and old 2005 model I really can't afford to spend too much money on new ECU's etc. Locost ideas please.

Antipolution could be the lambda going south, dodgy injector etc. Try scanning the OBD and check to see the lambda is toggling away nicely.

^^ what he said, you need an OBD reader with live data (some of the apps for the cheap bluetooth ones do this too)
live data can help show up some of the faults that haven't managed to generate a code.

eg. A while back my brother had just about given up sorting the emissions fault on a TU9 engine after replacing loads of bits - but the live data showed that the lamda sensor was pretty well stuck at one voltage and the temp sensor in the head was only reading 30°C - nether had failed in a way that generated a code, but both were feeding the ECU the wrong data which in this case made it run super rich.

So different symptoms? Loss of power gone?

Where did the coil pack come from and what make? Lots of cheap parts out there (and fakes) that are just wrong enough the trip a fault code but still work. You need to read the codes again. Also what codes did you clear before? Did you just get eobd codes read/cleared or the generic Citroen ones as well?

Ps. "Anti pollution fault" is the dashboard default message for any tripped engine codes.

Also have a look on http://c4owners.org/ where there is a wealth of information that is searchable for your issue

Post up the codes previously read off and the engine code (6th 7th and 8th of chassis number and will likely start N_ _)
If it's NFU there is a special spark plug (bosch FR78NX, supercedes to FR8SEO), using other plugs can cause misfire fault codes and cam phase sensor fault codes (there is no cam phase sensor, it is a function of the coilpack feedback, which does not function correctly while misfiring)
IIRC the cam phase sensor codes will not show up on a generic obd scan, only with manafacturer specific software.

Dave

As previously mentioned I changed the coil pack but the fault returned within a few miles. However, this morning when the car was started there was no warning light or fault code. Following a 40 mile journey it is still off, so fingers crossed. Thanks for your suggestions.