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I just had a Vagcom plug in as unfortunately my S4 is very sick, flagged up lots of faults Both front 02 Lamda sensors - no signal and charge control unit inoperative (is this the N75?????). I had both lamdas replaced last month with genuine stealer sensors but these fault codes keep coming back. Getting a serious loss of power, hesitation, and a slight missfire.

I have looked at the many posts regarding the N75 but still not sure if this is the problem. Would this cause the lamdas to cut out .......any ideas guys I'm seriously loosing patience here, if it is the N75 is this a DIY job??? and how much are they. thanks in advance

I think going by other comments on here that a trip to MRC would be worthwhile.

Sounds like a very good idea - if it will get me there cheers anyway

...a very easy swap out to replace the n75 - even i managed it. post your error codes in the DTC forum and you may get a more helpful diagnosis, it worked for my problems:

n75 part number and cost:

078906283B
£35.73 +vat

cheers just ordered 1, £35 cheapest part ever!!!! , will fit it tommorrow, thanks again

S4Daz wrote: cheers just ordered 1, £35 cheapest part ever!!!! , will fit it tommorrow, thanks again

yeah its cheap in the greater picture of s4 parts

the (one of a few) fault codes I had was:

17963 - Charge Pressure: Maximum Limit Exceeded


in the end i changed the original 710a's (7 years old!) to 710n's and swapped out the maf (again 7 years old) and finally the n75 valve, which looked original ancient part as well.

you may have the same problem as i noticed when whipping out the n75, there's a hose underneath it that was snapped! see thread here

..but a bit of gaffer tape and its holding up if i get up tomorrow early enough im off to the stealer to get a new one. Note I havent changed any hoses so I can assume I didn't have any hose leaks but im going to replace them anyway as they looked like 7 year old rubber hoses do, i.e likely to go anytime soon!

I just changed the N75, dead right really easy DIY, pipes were ok by the way - done the MAf too, Boy what a diffrence!!!!, dont think Ive ever got full power out of it till now. cant stop grinning!!! want lots more power, give me more power

Clean bill of health also means a trip to MRC for sure.... thanks again Mr Mcd

S4Daz wrote: Clean bill of health also means a trip to MRC for sure.... thanks again Mr Mcd

Its good when you clear down the codes and they don't re-appear, I ordered another £100 of hoses/pipes on Saturday so am going to do them anyway...but good news all the same, you can feel comfortable giving it some welly down to MRC

Incidentally, I also noticed my mpg has gone UP! I used to average 22mpg now Im doing 26/27mpg