Discovery Series 1 4.0 V8 'Check Engine' Question

[Crs]

I've got a US spec 1997 Discovery V8 automatic (called Ming).

It's been putting on the yellow (non flashing) Check Engine light.

I tried out a new OBD2 scanner and I'm getting codes P1172 and P1179. In human language that means the car is running too rich in both banks and there is a 'Maximum Negative AMFR Correction Fault'. The car still seems to drive fine. I ran some further tests and I think the O2 sensors are good, but I may not have been reading it properly.

I've done a little googling and 'they' say the MAF sensor may need cleaning/replacing and/or there may be a leak in the air induction system. It also seems that a decent tune up is in order.

Any suggestions? Any tips/tricks of the trade on how one would begin on this job list? Suggestions welcome. Thanks in advance. :D

P.S. Oil has recently been changed. All fluids are topped up.

[archaeology_student]

Oxygen sensors should be replaced every 50-60,000 km... I would replace the lot... NGK 25044 on Amazon, at $50 a piece it's cheap and easy, and improves fuel economy... if the codes are still there afterwards I would look at a new MAF ;)

Just replaced my O2 sensors and cleared the codes after my check engine spat out a bunch of O2 related codes and the truck runs beautifully now ;)

[Crs]

Thanks for the info. It turns out the MAF needed a good cleaning and there was a hole in one of the air inlet pipes. I'll find out the details when I pick her up.