P420

[Gaz mr-s]

How about brake cleaner or MAF cleaner?

Yep, I'd think so.  That's the sort of stuff used on intake testing anyway.

[shnazzle]

Yep, I'd think so.  That's the sort of stuff used on intake testing anyway.

Just make sure you keep hte brake cleaner away from rubber lines and sparky bits  It's super flammable

[Newbie57]

What am I expecting to happen?
Change in idle or a different graph output?

[shnazzle]

What am I expecting to happen?
Change in idle or a different graph output?

A very fair question. Apologies for leaving that out!

Yes, you should see an immediate response on the B1S2 reading toward rich. Entirely possible even that you'll notice the RPMs change.

[Newbie57]

A very fair question. Apologies for leaving that out!

Yes, you should see an immediate response on the B1S2 reading toward rich. Entirely possible even that you'll notice the RPMs change.

So tried this. No response that I could see from B1S2. Post cat sensor.No change in idle revs.
Should I be doing this at a higher rpm?

[Gaz mr-s]

I've previously suggested it could be the maf.   You mentioned you cleaned it, can you clarify you know it's the component at the top inside it, rather than the visible blob?

If you take the maf out again check that the o ring is intact.

If no issue there maybe go to Rhys & see if he'll lend you a maf.

[shnazzle]

So tried this. No response that I could see from B1S2. Post cat sensor.No change in idle revs.
Should I be doing this at a higher rpm?

Nope it would appear there's no leak then. That's good news.

See gaz's post. MAF is another good culprit.

It's a bit special because the P0420 code suggests a problem with the O2 sensor, but the O2 sensor could be downstream from the actual cause.
Much like how a bad foot can lead to back complaints. 
It makes the p0420 a bit tricky.

Especially, as Carolyn said, the MAF doesn't throw codes. Which is stupid in my opinion....

[Newbie57]

For completeness these are the old plugs I changed out

[Ardent]

They look in good nic to me.

As in engine happy.

[Newbie57]

Where I am now
Released the maf. No difference
At idle B2S1 voltage reads 0.01V to 0.04V
From what I read this suggest a very lean condition. Maybe exhaust leak, although I can't find it.
Once I lift the revs to 2k B1S2 follows B1S1 pattern voltage which suggests bad cat. Cat is only 1 year old and done very little milage. Still under warrenty from Cat2u.
Will see if I can borrow  a good cat from somewhere.

[Carolyn]

What do you mean by "released the MAf"?

[Gaz mr-s]

I assume it's meant to be 'replaced'.   What with, new or a known used one?

[shnazzle]

I would have replaced the post-cat sensor first.
Also, stupid question but...the wiring is definitely put back as it was?

[Newbie57]

I would have replaced the post-cat sensor first.
Also, stupid question but...the wiring is definitely put back as it was?

Post cat sensor is a quite new denso one. Looking at the traces from all the sensors I would say they are working.
Wiring is ok.

[Newbie57]

What do you mean by "released the MAf"?

typo cleaned it again

[Gaz mr-s]

You've cleaned it, not changed it?

[Carolyn]

typo cleaned it again

I think it's time for a new one.  It's the only way to know for sure.  Get a Denso.

[shnazzle]

I think it's time for a new one.  It's the only way to know for sure.  Get a Denso.

Or meet up with another owner with known good and swap