check transmission code E displayed

[ls2002]

2002 LS 3.9 sport. Last week the check transmission and E code displayed. So today I took it to a couple transmission repair shops that did a scan. There were 2 codes a P0133 and a P0840. I know the P0133 is for the 02 sensor, the P0840 I was told is for the transmission pressure sensor, however one shop said it is inside the trans while another said it was on the engine. The car shifts and drives fine. I did do a search on the code P0840 with no results found. would like any and all info for this code. Thanks