2.0 golf gti lambda sensor fault

[kev3000gt]

Hi, im helping a friend fix his car, its a 51 2ltr gti, i hooked it up to the lappy and the fault code showed sensor 1 was screwed and sensor 2 was slow to respond. We bought a replacement for s1 but when we went for a fit, the plug was slighly different to original. it still had 4 wires, same colours, so i cut and soldered the old plug to the new cables. Reset the fault codes, engine light went off, took it for a spin and the light came on after about a mile.

so, is there any difference in the actual sensors from s1 to s2? or do you think they are basically the same thing? The only lambdas on ebay which state s2 are 90 quid, the cheap 1`s are 30 but dont state a position. i`m aware that a bosch would be best but he is looking to sell the car after weve got it fixed up.
Thanks, kev

[itavaltalainen]

yes the sensors are different, generally bank 1 is used for fuel mix adaptation and can resolve small changes in exhaust oxygen content, bank 2 is a step sensor as it only needs to make sure that the cat works and does not need the same kind of resolution as you would for bank 1.

what faults does it show now??
 

[kev3000gt]

i havent plugged it back in yet, he lives 30 mins away and i didnt have my laptop with me when i swapped the 1st 1 

http://www.ebay.co.uk/itm/171105209972?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649

that listing seems to cover pre and post cat?  i should plug it back in and check the number of cables in the 2nd sensor i guess? Both sensors are bank 1 as its 4pot, but they show up as s1 and s2

[itavaltalainen]

Well if ebay seller says his (chinese??) part can be used for both Bosch, VEMO, Delphi and VDO all got it wrong.... cos they all have two different sensor for pre and post-cat 

check what the fault codes are now and go from there.... second lamda fault could also be dodgy cat btw....

[danny_p]

1st sensor is a wideband  they arn't cheep

the 2nd is just a generic bog std narrow band lambda  they are pritty cheep

[Ben@VWH]

Post up the fault code you're getting as many lambda related codes are actually due to air leaks as your ecu will flag a fault if your fuel trim exceeds 20%.