Land Rover Repair: 2000 Disco 3 amigos/Wheel seal cause?, mass air meter, grease seal

Question
I have a 2000 Disco 2 w/ 4 liter Bosch engine. It has 113000 miles on it. I just purchased the truck and it is my first LR. Well kept vehicle. I have the 3 lights on as well as check engine. I discovered grease soaking the driver side rear wheel when checking the brakes for the ABS issue. Looks like a grease seal. After reading a lot of the posts I was wondering if it is possible that this could potentially be the root of my problem. i have several OB2 codes present as well. the usualy O2 sensor etc. Also have the P0734 gear 4 incorrect ratio. Noticed a post that the MAF sensor can cause this problem. I also have the idle speed control , fuel air metering code. I will fix the wheel seal first. Just wondering if you had experienced this with the rear wheel seal leaking making the lights come alive? Also after repair can the lights be reset with the temporary disconnect of the battery as is typically done with the service engine light.

Thanks a bunch. I have learned a ton of things about LR from reading the posts. I work on my own stuff and put myself through college working as a mechanic. I am handy at best but these LR's are a new game for me. i have to say that I love the engineering on these things even though there are bugs. Had a sunroof leaking and after looking forever found that the drain tube was broken off. Never even seen a drain on a sunroof.

Thanks a bunch!!!!
Chad  

Answer
Unhooking the battery won't clear a check engne light on a 1996 or newer vehicle.

You need the Land Rover test system to check ABS codes, and I doubt if the greasy hub would set a light but it's possible.

The 4th gear ratio code does point to a mass air meter problem.