Hi I am new to forum. I have purchased a 1998 range rover p38 4.6 hse with 135k on it. It has a check engine light on snd seems to be stuck in 3rd gear as well as a clicking noise coming from the becm. I ran the code and it came back p1777. I erased the code and it came back again. I checked the transmission plug located behind the driver side head it seemed to be in good condition. I have an extra transmission controller but haven't installed it As well as access to a spare becm . I am unsure what my next steps should be. Any help or advice is greatly appreciated. Thanks in advance.