Hi Everyone,

I'm new to the forum. I recently just bought a 1996 A4 2.8 and when I was trying to get it smogged the check engine light came on throwing out the code P1109, which has something to do with the O2 sensor. My question is how many O2 sensors are on the car, because the person who I bought it from brought it to a shop and they changed 2 O2 sensors. However, when I failed smog, I brought it back to the same place, they said there were 2 other ones that they didn't change. So, are there a total of 4 O2 sensors? I always thought most cars only have 2 sensors and I don't have a manual to check... I hope they aren't ripping me off...Thanks

 

there are 4 O2 sensors on the V6 and 2 catalyst's, the code P1109 doesn't exist so I wonder if you have been ripped off the codes for the HO2S ( heated O2 sensors ) start at P1101 up to P1107 then P1110 to P1120

 

4 oxygen sensors.

P1109 is bank 2 post catalytic converter oxygen sensor. There is either corrosion in the wiring, a loose connection, or an exhaust leak between the pre and post catalytic converter on that side.

 

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