advice please 02 sensor codes

[Lazer Viking]

okay, 01 a4 1.8t.. replaced both 02 sensors and maf, was throwing p0420.. no big deal cat is probably toast, put some spacers in and and good to go right ?

wrong. .. after i put the spacers in got 2 codes p0136 bank 1 sensor 2 voltage too low p0140 no activity detected, i figured i didnt drill out the spacer out enough and it was grounding out, so i drilled it out.. good to go for a couple key cycles and the p0136 code came back..

what gives ?

this car is a never ending stream of codes, 9 months of ownership and the check engine light has been out for a combined total of like 50 miles

[walky_talky20]

How many spacers are we talking?

[Lazer Viking]

2.. Is your thought it's spaced too far away?

[thenj3]

i ran two spacers with no problems. i think its grounding out somewhere

[walky_talky20]

I would try with just 1 spacer to start.

I don't think this is a signaling issue. I think the sensor just isn't reacting to the change in O2 in the exhaust stream. The code is caused by it's lack of reaction, probably due to being too far removed (or blocked) from the stream. The spacer(s) might just need drilled out a bit more to get some flow up in there. Not too much though, obviously. In any case, the spacer isn't always a sure bet.