Greetings, My son has a 2002 GTI 1.8 turbo. The EC light came on and the obd code is PO420 and PO171. I think this is the O2 Sensor. My question is which one? Is it located on top of the Cat-converter? Thanks, Darkside....
Dont know your car or the error codes you've found. Ive just had to sort out the O2 sensor on my mk3 2GTI. Ive only one, thats just before the cat. Mine is on the side of the pipe so it was amazingly easy to get out. If you've got 2 there will be one after the cat as well Check the wiring out first before condeming the sensor (s) Mine had been replaced at some point and it was a bit of a pikey job. I replaced some of the loom and cleaned up and sealed the multipin connector. The cars going better than every now. You could meter your sensors, you should measure aroud 0.45v when things are running ok. It swings from around 0.2v to 0.8v but you will only see that on a scope, vagcom or the like.
