No O2 sensor activity

[mike's machine]

I checked all the signals on wires and they are perfectly working.
But the vag-com does not read any activity (0%).
Could the ECU be bad???

[mholme]

Are you getting a "No activity" code or are you actually trying to log the sensors?

[mike's machine]

there are only half of the voltage should be read.
on the sensor and the plug connector, and the wires going into ECU read the voltage just fine.

[AudiHolicS4]

Are you getting a "No activity" code or are you actually trying to log the sensors?

what if you are getting a no activity code does that mean they need to be changed because after i did my exhaust i get no activity codes from all four sensors and they were fine before im not sure how brittle they are but i just dont see how they all could have went bad at once plus im getting a low input maf code and i put a new maf on and still same thing havent checked the wires but like i said everything was fine before the downpipes and exhaust were put on....sry for jacking your thread

[mholme]

what if you are getting a no activity code does that mean they need to be changed because after i did my exhaust i get no activity codes from all four sensors and they were fine before im not sure how brittle they are but i just dont see how they all could have went bad at once plus im getting a low input maf code and i put a new maf on and still same thing havent checked the wires but like i said everything was fine before the downpipes and exhaust were put on....sry for jacking your thread

If you got the codes only after the exhaust work, I would think your connections are bad. The rear O2 wiring isn't that long and if the sensors are put further downstream, you can easily damage the wires

[AudiHolicS4]

thanks for the reply but what about the ones upstream how would they just go bad like that

[mholme]

thanks for the reply but what about the ones upstream how would they just go bad like that

They wouldn't. I'd suspect the same wiring issue. When you removed the downpipes, were the O2's already out? Maybe the wiring got damaged? I always think that if something in the general area of where you last wrenched is suddenly no longer working, it's probably a direct result of the wrenching.