Pollution Cat Warning

[Steve_B]

The wife’s 1.6, petrol, 53 plate 206cc is showing the antipollution cat fault.

I plugged in my scanner and it gives the the P0402 low cat efficiency fault code (see picture). However the live readings from the O2 sensors (other picture) are sort of what you would expect, varying upstream of the cat and steady downstream.

Although I would assume some slight variation in the No2 sensor, I would have thought that if the cat was failing the voltage would closely track the No1 sensor.

Thanks in advance of any enlightenment.

Fault codes.png

O2 graph.png

[Capncol]

Looks like your post cat sensor is knackered.

[gazza82]

Lambda's have pale blue and pale green plugs .. (can't remember which is which) but I have seen a couple of cars with them bot the same colour .. which means one has the wrong length cable as one is longer than the other to reach (rear one probably thinking about it!) .. and that is critical to how the lambda works ...

Also not all after-market lambda's are the same as OEM .. once had a NTK lambda on my Alfa which was a complete pain and forever throwing error codes. Turned out the ohm rating was HALF that of the Bosch original .. and that was fitted by an Alfa specialist .. Suffice to say it now has a Bosch one and I fitted it!

[Steve_B]

Sorry for the delay in updating this post. After asking for advice, I generally try to follow up on what I have found in case it might help others.

This time a family issue (none car related) came up so my wife took the car into a local garage. Their diagnosis was a fault cat. They changed this, but I noticed that they have also changed the second oxygen sensor although there is no mention on the bill.

The problem has gone, but I can’t say conclusively which it was.