have a4 2598cc petrol with abc engine .. b5, obviously ..

miserable co emission figure .. ecu warning me about g39 lambda ..

as car has done 160k miles, and probably still on original lambdas, will change all ..

question .. how many probes does this engine have ?. i am guessing at 4 (2 exhausts, so 2 pre and 2 post cat) .. ecu did not distinguish which g39 lambda is iffy ..
second question is .. where are they located on this car ?.

any help most appreciated ..

thanks ..

(was going to replace maf too, but discovered does not have one!)

 

Get under the car and look at the exhaust. The post-cat sensors are in the tops of the pipes, mounted vertically. The pre-cat sensors are seen by dismounting the coolant expansion tank and air intake pipe and looking down just past the exhaust manifolds.

 

found the front 2 ..

also my bellie will not allow post cat to be discovered w/o just need to jack-up the car ..