O2 sensor check engine light?

04-13-2010, 01:31 AM
So I have an 02 GTI (1.8t) and I am running without a catalytic converter so I bought one of these spacers to try and rid my self of the CEL


Apparantly I still need a cat; the spacer is meant to be used with high flow cats.

I ended up also replacing the rear o2 sensor. Before using the spacer I was receiving an obd code that made sense (catalytic deficiency or something) now I am getting codes

P0138 - Circuit High Voltage (Bank1, Sensor2)


P0141 - Heater Circuit Malfunction (Bank 1, Sensor 2)

I think this might be due to my test pipe; the pipe is oriented so that the o2 sensor bung faces towards the ground (o2 sensor faces up) so with the spacer installed a lot of water (I think?) is getting trapped in the spacer thus drowning the sensor and shorting it out? Could this be the case? I am not getting any cat. deficiency codes. If I had the test pipe turned so that the bung points up (o2 sensor would face down) would that help?

here is a pic (similar) of what I mean by o2 sensor bung facing downward


something like that...


04-13-2010, 11:25 AM
You need your CAT back. Your CAT converts unburned fuel into water along with evaporating it into carbon dioxide. If you don't run a CAT on modern vehicles at sometime you will get CEL's. Go get yourself a high performance CAT to get rid of your codes and get more power to your engine.

04-13-2010, 04:25 PM
So is that what is causing those codes? The thing is, without the spacer, I received codes that claimed catalytic inefficiency...makes sense, but with the spacer installed, the sensor is shorting out...this is what I am wondering...

even with a high flow cat, I will still get the CEL, thats where the spacer comes in, but if water is still going to build up in the spacer, I would need to turn the pipe wouldnt I?

04-13-2010, 04:48 PM
Your going to get water build up. It's worth a try to turn it, but I wouldn't count on it fixing your're CEL's. You might have to go back to OEM CAT if you still have CEL's .

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