[Frslam]

Hi Peeps, got a question regarding Post Cat O2 Sensors. I get the error codes P0420 and P0430. I used a SNAP-ON Diagnostic tool to graph the sensor activity.
When I go on a long drive (100m +) the EML normally switches itself off then when I revert to shorter journeys, it usually comes back on (within 75-80 miles or so). Car has just passed it's MOT - emissions have barely changed over the past 5 years going by the MOT Emission test - I can clear the error codes knowing it'll be a while until they pop back up again.
The SNAP-ON graph does show some activity and I'm wondering if anyone knows - is this likely due to failing Post Cat Sensors? This started happening after Halfrauds did an oil change and threw out the Oil Filter Housing 'cage' along with the old Oil Filter, upsetting the VANOS System, making the engine run a bit rich. I have since replaced the Oil Filter Housing Cap/Cage. Many Thanks

[therealdb1]

Mmm could be your Lambda sensors are contaminated or on their way out. They are running close to their upper limit. Possibly much of the time they are within the limits set but when you give it a blast it pushes them over the edge although I would have expected a prolonged motorway run might do them a favour.
It depends how worried you are about setting the EML now and again since they obviously were good enough to get you a new MOT.
If it was me I'd probably leave them until the weather warms up a bit and then fit new ones

[Frslam]

Originally Posted by therealdb1

Mmm could be your Lambda sensors are contaminated or on their way out. They are running close to their upper limit. Possibly much of the time they are within the limits set but when you give it a blast it pushes them over the edge although I would have expected a prolonged motorway run might do them a favour.
It depends how worried you are about setting the EML now and again since they obviously were good enough to get you a new MOT.
If it was me I'd probably leave them until the weather warms up a bit and then fit new ones

Thank You. I do think it's Sensor 2 Bank 2. Wonder if the wee activity from Bank 1 O2 Sensor after the Bank 2 O2 Sensor is because compensatory effect? Like I said, Emissions are easily within the scope