# Cat Delete Caused Permanent Engine Light - How to Fix?



## Moon5 (Feb 25, 2015)

Recently deleted cat on my '08 2.5L and, as expected, the engine light is now permanently "on". I've coded to confirm there's nothing else causing the light.

Question is, how can I hack/fool the ECU so that it doesn't detect the delete?

I can live with the light, but would rather not. 

Thanks,

Matthew


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## gugu1981 (Jul 25, 2011)

i think most tunes have the option for catless/highflow cat. Or you can try a o2 spacer that basically gets the rear o2 sensor out of the exhaust stream, thus tricking the ECU into thinking that everything's peachy.


Peter


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## DerekH (Sep 4, 2010)

I agree with Peter, your best bet is probably the tune. but you may be able to sort it out with an O2 spacer.


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## [email protected] (Aug 18, 2011)

One of these *might* help, but it's usually only effective when you have a high-flow cat: http://store.blackforestindustries.com/oxsesp.html 

No cat almost always requires a tune, from my experiences, but YMMV.


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## Moon5 (Feb 25, 2015)

*Spacer*

Think I'll try the spacer approach first. Are you talking about removing the sensor from the housing/mount and letting it be exposed to atmosphere instead? If that's the case, I'll just need to thread something into the mount opening to cover that opening?


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## [email protected] (Aug 18, 2011)

Moon5 said:


> Think I'll try the spacer approach first. Are you talking about removing the sensor from the housing/mount and letting it be exposed to atmosphere instead? If that's the case, I'll just need to thread something into the mount opening to cover that opening?


This spacer goes between the exhaust pipe and the oxygen sensor that was after the cat which is the furthest sensor down the exhaust system. Simply remove the oxygen sensor, thread the spacer into the exhaust and then reinstall the sensor into the end of the spacer. This will keep the sensor out of the direct stream of exhaust flow which may trick the sensor into thinking that the cat is functioning properly.


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## graffswag (Apr 22, 2015)

It also works for if your cats die prematurely, due to prolonged misfires or other conditions...


2012 VW B7 -Passat
1998 Merc W140 -S320


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## tchilds (Nov 21, 2008)

Somehow my tuner removed my CEL. I just asked while some guy was remotely tuning my car over the phone and boom he turned it off np. They told me it was for track use only etc etc though when they turned my CEL from my test pipe off. However, I've heard mixed results on this method. My 02 ended up shorting out the heater circuit and now has a cel until I replace it or my ECU burns out. Apparently, on the early MKV, that happened a few times to some ECU's.

I can't complain, my $180 02 sensor lasted about 120,000 miles with SRI and test pipe on my 09 before the heater circuit CEL popped up permanently. 

I've seriously been thinking about taking apart the cluster and putting stickers over the stupid CEL spot and a couple others. I figure with aftermarket gauges I don't need them anymore anyway. My wideband will tell me if my motor is dieing and any time the motor throws a CEL it basically goes into LIMP MODE if necessary anyway.


SPACERS NEVER WORKED ON MY 2009 PERIOD. Don't forget that cat you rip off is worth a nice chunk of change if sold in the right place.


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## brad131a4 (May 21, 2003)

Ok just a little late to the show on this one. I still have a hard time understanding the mentality of removing the cat for some unfounded performance gain? That and causing your car to run more bad emissions out the tailpipe.:banghead:
Seems to me replacing the cat with a lower restricted one than you have now would save you time and money. Over trying to trick and fool the ecm into thinking there is one there.
No I'm not a tree hugger by any means I just have a hard time watching people go down the same stupid path.


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## DerekH (Sep 4, 2010)

I run a high efficiency cat and i sill needed to get the code dealt with.


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## graffswag (Apr 22, 2015)

You need a de-fouler. 1- Take out the secondary O2 sensor. 2- Install de-fouler where the O2 went. 3- re-install O2 sensor to de-fouler....... It also works for if your cats die prematurely, due to prolonged misfires or other conditions...


2012 VW B7 -Passat
1998 Merc W140 -S320


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## graffswag (Apr 22, 2015)

Now erase MIL/check engine light with an OBD2 Scanner


2012 VW B7 -Passat
1998 Merc W140 -S320


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## graffswag (Apr 22, 2015)

Hope it works out for u


2012 VW B7 -Passat
1998 Merc W140 -S320


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