CO readings Hi 0.96% Vol

[uncle]

Just had my MOT and the CO2 readings are high

First Idle test 0.86%
HC 94
Lambda 0.998

Second idle test
CO 0.64%
HC 170
Lambda 1.007

I have a 200 cell sports cat fitted and REVO MAP and it has passed the MOT for the last few years with this fitted without any problems at the same MOT station..

The MOT station has told me they are 90% sure it needs a new CAT, which i don't mind replacing as long as it is that so I went home and checked for any fault codes.

I few months ago the v clamp split after the cat and the v clamp was replaced but the exhaust had a small leak at the joint and i had the engine fault light on and fault code P2096 the leak is now repaired and the engine light is now off after it was reset.

After it was reset the engine light came on once then went off and has not come back on.

I have just checked my codes after the high CO readings and have found that the P2096 "Post Catalyst Trim System too lean Bank 1" is shown in stored codes and Pending codes although i do not have an engine management light on.


Now im not sure if it is a sensor that is causing the Hi CO and this is why i have code P2096 or is the faulty CAT causing the P2096 code. I would have thought that a HI CO means the car is running too rich and yet the post CAT sensor suggests the car is running lean, could it be the sensor is faulty and telling the car to run richer which is why i have the HI CO and P2096 fault. Does the post cat sensor adjust fuel trim?


Im sure they must be related. anything else I can check. I have DashCmd app on my ipad so i can check quite a few things. Want to get the car sorted as everything else passed on the MOT with no advisers just the emission CO reading being high. I don't want to spend several hundred pounds on a new 200 cell cat if its not that.


This is on a SEAT Cupra TFSI 2008 and i know we share the same engines and i hope somebody here can help me I don't mind me posting this in the GTI forums,

[pudding]

If your post cat fault code was current, you would have the EML on.  Sounds like it's a historic code.  What Revo stage is it?  They normally code the rear lambda out I thought?

Either way, 1% CO at idle is massive.  That's 1980s car levels!!  Stock cats = 0.01% CO.  Poorly made sports cats manage 0.1% and is the pass limit. 

Your cat is probably just completely shot and not catalyzing at all.   Have you got a digital thermometer?  You can test the cat by holding the rpm at 2000 and measure the temp of the cat.  The exit should be considerably hotter than the input.  If it's the same temp both ends, it's f'cked.

[uncle]

Thanks for the reply pudding

It has a Stage 2 Revo.

The CAT has passed the last three MOT's with values in limit. 

I believe the fault codes are historic as I didn't have an EML light on and it was due to the previous leak after the CAT which was resolved a couple of weeks ago. I know that REVO map out the second 02 sensor but i think that's for comparison with the Pre CAT sensor.

I read today that when a MAP is used to not throw out the fault code for the second O2 sensor you can still have codes and EML light for high oxygen content (Lean Mixture) as the MAP doesn't take this function away.

Im tending to think that the Fault code was for the original leak after the post CAT joint leak and the high O2 reading is because my CAT is done.

New CAT has been ordered and will hopefully be fitted this week.

[pudding]

That's the thing with aftermarket 200 cell cats.  They're borderline from the get go and progressively get worse, especially with the over rich fuel mixtures remaps chuck into the exhaust.

Pretty sure Revo 2 does include a code out of the second lambda, or maybe it's only 2+ since a full exhaust and decat is a prerequisite?.  Anyway, it's a simple on/off byte in the software and if set to off, the ECU no longer concerns itself with the second lambda's readings.  That's a Bosch thing, not a Revo thing.

Anyway, I hope the cat sorts your issues.  What one are you going for out of interest?  My APR sport cat is useless and I also want to replace it with something that works.

[Dan_FR]

Not quite as simple as that for the second lambda - it's only a byte for the EML for cat efficiency. Revo Stage 2 and higher includes this, but the second lambda is also used for lambda control which is why the sensors still need to be connected and fitted in the exhaust, otherwise you would have multiple faults for open circuits etc.

Revo software will not affect the occurrence of a high oxygen fault code.... This is nothing to do with a de-cat.

but yeah sports cats are a waste of time.... Barely pass in year 1 (unless hot) but within a few years.... The quality of the precious metals used in aftermarket cats is nothing like those used in the original