Lambda fault codes

[the stig]

Last week my EML light flashed up and having taken the car to Audi they have told me that this could cost in the region of £300 to £800.
I have managed to get hold of the fault codes and would be interested to know which sensors these are and which colour codes they have so i can buy them and fit them myself. Then all i need is the fault clearing from the ecu.
The codes are P0154,P0159.
Any ideas would be a great help and also a rough price might help me sleep!:confused:

[Sloggs]

These may help you...

http://wiki.ross-tech.com/index.php/16538/P0154/000340

cant find anything for the other code.

[the stig]

Thanks Sloggs,i had already found that info but the one you gave is very helpful. Myproblem is finding out what colour the connector is on this sensor so i can buy another. Cheers