Catalyst System Error

[pandahouse68]

I reckon Lambda sensor and Oxygen senor are the same things 

and I have the same fault code P0420 too

Is yours a perminant fault code or intermittent? Do you get any warning lights? Mine doesn't?

yes ,warning light on and a running a stock exhaust system also just passed both the MOT emission test
and VCDS readiness test.
http://www.ross-tech.com/vcds/tour/readiness.html
and I believe there's nothing wrong with CAT or two Lambda sensors.

[xxx_mojo_xxx]

I think I'm going to replace my coil packs in the first instance to see if that improves matters.

My car has done close to 75k, and they may be one on the way out.  I suspect unburnt fuel caused by poor ignition sparks may cause this.

[Saintsteve]

I think I'm going to replace my coil packs in the first instance to see if that improves matters.

My car has done close to 75k, and they may be one on the way out.  I suspect unburnt fuel caused by poor ignition sparks may cause this.

Let us know how u get on. mine were changed as part of the recall about a year ago. No miss-fires  logged but could be a possibility. 

[pandahouse68]

yeah, please keep updated

[xxx_mojo_xxx]

yeah, please keep updated

Will do...should have a replacement set in the next couple of days.

[xxx_mojo_xxx]

Replaced spark plugs, coil packs, and petrol filter.  Car appears to be noticeably better and running a lot smoother.

It's too early to say if this has eradicated the issue. Will keep everyone posted.

[xxx_mojo_xxx]

Not wanting to tempt fate, but I am glad to report that the issue has been sorted.

Must have been either a faulty spark plug or coil pack.  I'm more inclined to say it was the coil packs.  Car has been driven over 600 miles since the replacement and its running like a dream. 

[Rav2011]

Hi Mojo,

Please can you tell me if you have a lambda spacer in place (post-cat sensor)?

Has you car been flashed to stage 2?

I get the same problem if I remove my lambda spacer. With the lambda spacer the car complains about the B1 S1 reading too rich?


My coil packs were changed under a recall last year and the spark plugs I changed to Denso's.

[xxx_mojo_xxx]

Hi Rav,

My car has stage 2 remap.  Not sure if my car has a lambda spacer - is there a way I can check? I did have Denso spark plugs originally, the IK24s.  I went back to OEM.

Hope this helps.

[Rav2011]

What OEM plugs you got?

[Saintsteve]

I had NGK 8 plugs after some people were raving about having cooler plugs. I reverted back to Bosch oem 7's and no longer suffer with the same warning error as yourself Rav.
Hth

[Rav2011]

Thanks SaintSteve, now I'll need to find some cheap!

[xxx_mojo_xxx]

What OEM plugs you got?

Standard Bosch ones from the VW dealership.

[Rav2011]

Hi Mojo,

The lambda spacer is basically an extension that fits onto the post-cat (after cat) sensor. Lambda spacers can be L-Shaped or a straight fit, some are slightly angled.

It forces the lambda sensor to sit out of the exhaust as opposed to directly in it.

Please can you tell me if you anyone has one of these fitted to the exhaust and has been able to overcome this error?

[Dsg steel]

Had this problem and ounce I fitted the stealth 42 spacer no more engine light