Land Rover Repair: 99 Discovery II Service Engine Light, spark plugs champion, vacuum leak

Question
My service engine light came on.  The first fault code was related to the O2 sensor Bank 1.  I changed the spark plugs (Champion 7318 which is supposed to replace the RC11PYPB4 mentioned in the manual) and air filter. The fault code I receive then is a lean burn code for bank 1 and 2.  I have checked for a vacuum leak and can not find anything.  I removed the sensor and tried to clean it with compressed air.  I checked fuel pressure which is between 52 - 50 PSI.  No changes, under varying driving conditions the light comes on.  With a different scanner I furthermore saw yesterday additionally to the lean burn bank 1 and 2 a code P01668 (mfg aux code).  Do you have any idea what this code is (local LR dealer is not cooperating:-))?  Any suggestions what to look for?

Any help would be greatly appreciated.  Thanks in advance, Michael

Answer
Hi Michael,

The code you describe is new to me.  P01668 has 6 characters and I always thought OBDII was limited to 5.  I did look up P1668 (dropped the 0) and it states "Anti-Theft Alarm serial link faultDrive cycle A:Signal out of range - above maximum".  Don't think this is related to your 02 sensor flagging a problem.

Too bad your dealer is not cooperating with you. Can you find a local mechanic that can help track down this problem?

Regards,

JohnMc