theodore

i have been battling a pair of codes for about 1 1/2 years now and i think it is time to resolve them.. does anybody know what the rear o2 sensor does. does it matter how far back the sensor is because i moved it further back when i had my downpipe put on. i have a highflo cat and i am 2.5 from the turbo back. if it just a matter of exhaust gasses i may just go to a standard 2.5 cat but the debate is whether i will need to go back to a factory cat and have another custom down made from ther back.

thanks

andrew

Digit@lex

What pair of codes have you been battling?

The post cat sensor is used for emissions and cat efficiency verification.

theodore

16524 - Oxygen (Lambda) Sensor B1 S2: No Activity
P0140 - 35-00 - -
16806 - Main Catalyst: Bank 1: Efficiency Below Threshold
P0422 - 35-00 - -

the first goes from intermittant to no activity at times.

Digit@lex

It needed a replacement. The post-cat sensor is mainly there to give you headaches during emissions testing days as well as cause a CEL. ;-)

When you say that you put if further downstream, were the wires extended? That may be the source of the issue as far as the 1st DTC. The second DTC is most likely due to the HFC. I believe I had a similar DTC occur every now and then but it was minimized after implementing a "mechanical" fix--two spark plug defoulers attached in tandem to the o2 sensor. It basically brings the sensor further from the exhaust stream so it just sniffs enough exhaust fumes to think it's within spec.

theodore

http://forums.vwvortex.com/zerothread?id=1366095

is this the mod you choose or did you do something different. i found that the spark plug arrester had to be drilled more to almost the point of making the threads real thin to attach the arrester to the exhaust.

i did extend the wires and i have thought the open would be the wires but the every so often intermittent signal always threw me for a loop.

why can't someone develop the perfect ecu trick for our cars and charge me 500 for it

Digit@lex

Haha, I was charged or $16.97 for this mod...2 defoulers and the 1/2' drill bit. ;-)

theodore

does the o2 fit perfect inside or is it a struggle??

Digit@lex

I have a 99.5 and the dome style O2 sensors fit just fine after drilling out the defouler. The purpose for drilling it out is to allow room for the dome to fit in. The thread size is the same so it is screws right in.

theodore

it's not a perfect fit. the o2 has lip that makes it a tad larger and yes it is a thread type. the tip sticks out about 3/4" with the lip so i would need to thin the defouler a bit to get it correct.