I have a 2000 disco 11 and just failed an emissions test due to codes p0171, p0174, po327, and p0734 The first two are bank one and bank two system too lean. Iam changing the spark plugs now. Can someone advise me on eliminating this problem and then how to clear my service engine light. Also the p0327 is knock sensor circuit low input. What the heck? I have seen the knock sensors but do they go bad or just get corroded contacts? And finally the last one is gear 4 incorrect ratio. I am not sure what to do about this issue. Any help with these issues is appreciated and also thanks to whoever host this site. You have saved alot of people alot of money.

 

Welcome DB!

PO 171 & 174 are lean codes. Not bad plugs, they would throw rich codes. Look for vacuum leaks especially around the air box. Bent over tabs allow unfiltered air to contaminate the air flow meter. That would also result in trans codes. AFM & air box lid replacement will be required if that is the case. Engine codes can be cleared by any OBDII reader. Trans codes can only be cleared by Dealer Test Book or equivalent.
Disregard any erroneous knock sensor codes.

 

I agree with bait, your MAF has failed, do you change your air filter when it is dirty, or are you using a K&N, either will kill the Maf.
Go on line to Rover Connection, DAP or Atlantic British and chec out their prices, should be in the $120 range. Then have some clear your codes, many of the better hand helds will do thi as will of course thge test book.
Mike