94 xj trouble codes

ok, trouble codes
22** ECT Sensor Voltage Too High (or Too Low) Engine coolant temperature sensor input above the maximum (or below the minimum) acceptable voltage
and
51** Fuel System Lean A lean air/fuel mixture has been indicated by an abnormally rich correction factor

Im looking to buy this jeep and it starts good, and runs great, but it idles at around 2grand, and the temp guage never really rises, maybe just a hair.

So, just wondering what i need to fix or check with theese codes it gave me!
Thanks

Code 22 was cured by a $20 dollar new coolant temp sensor for me... Code 51 might be the result of the bad sensor making the engine think it is running too hot or too cold... I'd put a new temp sensor in it and feel pretty confident that would fix both codes. If it does not, you are only out 20 bucks. The temp gauge reading is even more evidence of the need for the new CTS...

Test and or replace the coolant temp sensor. Both codes point directly to that....