P0420

Yep it's a bank 1 code just came up on the car I just bought off the daughter for £500.

Now I know the car has just had the timing belt replaced so am assuming that the head gasket was replaced to as the valves got bashed. Added to this it did have some oil contamination in the coolant before the belt went that is no longer present after a system flush.

With that in mind I'm going to put a possible cat failure to the back of the line at the moment and thinking it may be a 02 sensor that has become contaminated?

Which 02 sensor would be the most likely to have been affected by possible antifreeze the one at the start and easiest one to get to or the 2nd one?

Also if it has been contaminated Or is suspected can it be cleaned and replaced to retest or should it be discarded I asking as if it's the 2nd option then its a trip to the garage to find out which one is failing or if it's the cat.

Cheers Billy boy

Billathome65 wrote:Yep it's a bank 1 code just came up on the car I just bought off the daughter for £500.

Now I know the car has just had the timing belt replaced so am assuming that the head gasket was replaced to as the valves got bashed. Added to this it did have some oil contamination in the coolant before the belt went that is no longer present after a system flush.

With that in mind I'm going to put a possible cat failure to the back of the line at the moment and thinking it may be a 02 sensor that has become contaminated?

Which 02 sensor would be the most likely to have been affected by possible antifreeze the one at the start and easiest one to get to or the 2nd one?

Also if it has been contaminated Or is suspected can it be cleaned and replaced to retest or should it be discarded I asking as if it's the 2nd option then its a trip to the garage to find out which one is failing or if it's the cat.

Cheers Billy boy

If its a 50:50 and you pick one to change, if your luck is like mine, it will be the other one

O2 sensor codes show up because there is an unacceptable difference in the signal, this may not be due to a faulty sensor.

It could be a different problem that is making the sensor give a signal that the ECU sees as out of range.

Can you clear the P0420 code?