second new o2 still have code melted cat? bad wiring?

[70 eliminator]

car is b5 s4 2.7 just purchased had cel and an bad sensor code no activity.
looked through records and found it had been replaced in last few months. so i was not optmistic but replaced it with a new sensor still have little to no activity
in replacing it i looked into the spark plugs and air filter general stuff...
also :
it hasent been tuned up recently and i found a bank 1 cat below effiency code

so i have a wild guess and allready have pipes so i may be able to fix..
i wonder if the pre cat is bad and partialy clogged causing a pool of gasses to gather its stuck at .434 volts and will move about .003 + or - from this number other side is responsive

so if its in a chamber of slow moving gasses it would have a damping effect on readings like the no fowler mod traps a small amount around the tip and it exchanges slowly so the readings are lazy to change possible???


any other ideas.

[hercfe]

it doesn't have piggies does it?

[70 eliminator]

not yet but if the pre cat is melted it will be cut out and replaced with a hollow chamber

i just cant see two sensors in a row having little to no activity....

[mholme]

A no activity code is most likely going to be a wiring issue.

[70 eliminator]

i get a voltage reading but it is pretty much stable... is there a fuze for an o2???

[mholme]

No fuse. There are 4 O2 sensors on this car so it's important to make sure that the codes you're chasing are for the right one. List the exact codes for us and it will be a lot easier to help you find the culprit.

[70 eliminator]

code action taken

17867 egt sens 2 purchased a pair of new egt sensors. yet to be installed

17125 tcc stuck off drive it nice add trans cooler start saving !!!!


16805 intermint cat below eff. bank 1 have used set of down pipes in garage

18032 mil cleared

16518 bank 1 o2 no activity previous owner replaced at 129k i just re did it at 137k sits at .43v

01211 belt tensioner ignitor rear drivers side?? have no idea what it is????


bank one is passenger correct!!

[orttauq]

Bank one is the right side, but is it sensor 1 or sensor 2?

Belt tensioner ignitor means the seat belt itself is probably no good. Car been in an accident?

[mholme]

16518 is no activity for the primary passenger side . Is this the one that was replaced? Was it spliced or plug and play? The below efficiency code for the downstream sensor on that same side could be a direct result of the primary sensor no activity code. There needs to be a specified difference in the readings between the two to not get efficeincy codes.

[megafreakindeth]

Niot to derail your question but torque converter lockup codes won't just go away. Certianly not just because you installed an oil cooler.

As for 02 sensor no activity, get a multimeter with a probe to pierce a wire. Find the o2 signal wire nearest you can to the ecm and see if it gives you a good reading. If its still stuck at .45v or so then the wires bad. If the signal is sweeping then the ecm is bad. Considering you just bought the car they probably were hesitant to do even the o2 sensor let alone replace an ecm. Most people with these cars don't do any maintain or fix anything that's broke. When they get a quote for 2grand their simple minds think its a better idea to spend 20+ grand on a new car.

[70 eliminator]

its sensor 1 and the pass has been replaced 2 times.same code

i know the tc code is going to become often and will never go away. but i hope to mitigate the additional heat generated by driving with a non locked up converter.

so you suggest following the signal back to the ecu. allong the harness pircing and testing for a break in the wire??
if the signal is changing at idle at the sensor connection then the ecm is toast..

great i was just looking at a chipped ecu.... and decided fixing the car was more important...

any idea what pin the signal comes in on i was looking at the diagram of the harness and cant follow the path i guess i will trace the wire color back to the ecu....

[70 eliminator]

just back probed sensor 1 bank 1 and the needle sweeps!!!!
back probed bank 2 sensor 1 and nada hooked up my live readout and b1 s 1 was switching and b2s1was not ....

people have been swaping the wrong sensor but the correct sensor for the code found.....

i swapped in the assumed good sensor i removed from the bank 1 s1 position that was less than 6 mo old... and the sensor is still not switching .on my live readout but i will back probe it soon.
it was an audi sensor and the wires were really twisted up from the last guy who worked on it. dealer i assume... one turbo was replaced at 10k

any way i am going to disect the harness on this sensor because i think it might be shorted. could this fry the ecu o2 circut????

[mholme]

A short at the O2 wires is usually good to pop the ECU fuse before taking out the ECU itself. Usually..

[CONTROL ONE]

Going to piggy back this thread as I just got a whole slew of codes after I swapped my downpipes.

Before: Zero codes for 3+ months

Now:
16538 P0154 - O2 Sensor, Bank 2, Sensor 1 (No Activity)
17528 P1120 - O2 Sensor, Bank 2, Sensor 1 (intermittent) ??
16518 P0134 - O2 Sensor, Bank 1, Sensor 1
17863 P1455 - EGT (doesn't specify which side)
16523 P0139 - O2 B1 S2 (Passenger side rear O2)

Now, to complicate things a bit I also had to mess around with the rear O2s as they needed to be extended to reach the new downpipes which brings up 2 concerns:

1. Would messing with the rear O2 sensor (rewiring) cause a 'No activity' reading in the front O2 sensor?
2. Do I even need defoulers on the rear O2s anymore? I was under the impression that if the O2 location is set further back, you no longer need the defoulers - is this true?

[mholme]

Going to piggy back this thread as I just got a whole slew of codes after I swapped my downpipes.

Before: Zero codes for 3+ months

Now:
16538 P0154 - O2 Sensor, Bank 2, Sensor 1 (No Activity)
17528 P1120 - O2 Sensor, Bank 2, Sensor 1 (intermittent) ??
16518 P0134 - O2 Sensor, Bank 1, Sensor 1
17863 P1455 - EGT (doesn't specify which side)
16523 P0139 - O2 B1 S2 (Passenger side rear O2)

Now, to complicate things a bit I also had to mess around with the rear O2s as they needed to be extended to reach the new downpipes which brings up 2 concerns:

1. Would messing with the rear O2 sensor (rewiring) cause a 'No activity' reading in the front O2 sensor?
2. Do I even need defoulers on the rear O2s anymore? I was under the impression that if the O2 location is set further back, you no longer need the defoulers - is this true?

I would go over all your wires and connectors again. You pulled the downpipes with the sensors in place, yes?

If you're not getting efficiency codes after the downpipe install, the ECU is satisfied with the O2 readings and you don't need defoulers.
First thing I would do is recheck all your wiring that you touched. Make sure the wiring goes to the sensor(s) in question and such. Also, clear the codes and see what comes back. You'll want to do that before replacing the EGT sensor anyway. And that is a passenger side EGT sensor code.

[CONTROL ONE]

Passenger side O2 is new
Passenger side EGT is new
Both Passenger side EGTs and O2s were removed before pulling downpipe

Driver side O2 was old, stripped and solidified in the stock dp. I had to remove it off the car, with vice grips and a blowtorch. This O2 sensor is now throwing two different codes.
Driver side O2 is original as far as I know
Driver side downpipe was pulled with O2 sensor in place but EGT was removed properly

Now, when I put the DPs back on and started the car, the passenger side EGT was smoking for the first 5 mins and then went away. What would possibly cause that? This EGT sensor is now throwing a code.

After clearing them, these are the only two that have come back and it hasn't thrown a CEL yet after ~15 mins of driving.

16538 P0154 - O2 Sensor, Bank 2, Sensor 1 (No Activity)
17528 P1120 - O2 Sensor, Bank 2, Sensor 1 (Open Circuit)

[mholme]

I'm not positive a no activity code throws a CEL. I would dig into the sensor wiring, it's really easy to do basic continuity/resistance tests. EGT sensors are very finiky. I replaced mine on one side and then the other threw a code within minutes. Was it a new sensor?

[CONTROL ONE]

I'm not positive a no activity code throws a CEL. I would dig into the sensor wiring, it's really easy to do basic continuity/resistance tests. EGT sensors are very finiky. I replaced mine on one side and then the other threw a code within minutes. Was it a new sensor?

I edited my post now with more info.

New EGT - refurb from Shokan ~2 months ago
The other EGT is probably original.
New O2 - new Bosch unit from a year and a half ago
The other O2 is probably original.

[mholme]

It's possible you damaged the sensor removing it. You can check your readings through VAG-COM and do the electric probes, but your edited info leads me to think the sensor is going to need to be replaced.

[CONTROL ONE]

Ya, I banged the crap out of it trying to get it out with the downpipe and the heat shield still attached.

Also, I'm sure it wasn't that good for it to heat up the dp surrounding it trying to get it out even after it was off the car.

I'm pretty sure I'm just going to have to get a new front O2 sensor, I just don't want the EGT code to come back on.

[mholme]

I'd just replace the O2 sensor, hopefully it's related to the mixture readings and won't come back after the O2 sensor repair.

[70 eliminator]

any other ideas besides ecu it only takes 10 minutes per side to swap o2 sensors though pretty easy. i am not looking forard to doing the egt though.....

[mholme]

An EGT sensor is no harder than an O2 sensor to replace in my opinion. I really don't think it's an ECU issue. Something is going on with your wiring.

[70 eliminator]

ok i guess i need to pin out the harness and figure out continuity...

[70 eliminator]

any body know what pin is signal wire at ecu???

or where i can find out...