I have notice my Discovery II has Been idling a little rough, also has not started on the first turn of the key intermittently. Have a feeling it is somthing to do with an o2 sensor and I am sure there is someone who can tell me exactly what to fix. It is a 2001 land rover discovery II. Thanks alot.

 

Use

http://enginecodemaster.com

To understand rover codes.
The codes for Rover in engine code master are from the Rave manual.

Put that site up a few years ago as I hate looking in books for codes.

 

The P0154 code is for the B2S1 O2 sensor. That may also be causing the lean code. The best thing to do would be, hook up a scan tool and watch the live data to see if the oxygen sensor is working when it goes into closed loop. Better to check it out before replacing any parts.

 

Went ahead and replaced all 4 o2 sensors since it is almost to 100k miles. Front passenger was the problem though. Had oil leaking into it. Idle is smooth again and codes are clear. Also I moved that plug with zip ties to keep it out of a small drip area.