02 Escape check engine light while in 4x4

Just started using the 4x4 in snow on an 02 v6 automatic escape, noticed that while using the 4x4 the check engine light flashes on and off after around 5-30 minutes of driving, after 4x4 was turned off the flashing continued for a few more minutes, check engine light has never went on the previous few months. On another issue does anyone know what causes occasional rough automatic shifting when truck shifts gears, sounds like a clunking noise when going up steep mountains, never happens on flat land or mild hills.

Tranny, how many miles? Last time trans filter and fluid changed? Checking fluid level when hot/running on flat surface, is it close to the top of the hatched area of the dip stick? It could be low fluid and when you go to steep angles it might be starving for fluid in the correct areas of the trans.
4X4, correct full time operation. Where you exceeding 35 MPH? The designers in their wonderful wisdom decided that you shouldn't need to be in full time mode when you go above 35. It will automatically kick out and go back to auto detect for wheel spin engagement of 4X4. But returning to slower speeds it doesn't usually return to full time mode. So they have it flashing the engine light and you have to manually reset the switch to auto, wait till it stops flashing, then you can switch to full time 4X4 again as long as you stay under 35. I always turn mine back to auto when I get above 25.

Tranny, how many miles? Last time trans filter and fluid changed? Checking fluid level when hot/running on flat surface, is it close to the top of the hatched area of the dip stick? It could be low fluid and when you go to steep angles it might be starving for fluid in the correct areas of the trans.
4X4, correct full time operation. Where you exceeding 35 MPH? The designers in their wonderful wisdom decided that you shouldn't need to be in full time mode when you go above 35. It will automatically kick out and go back to auto detect for wheel spin engagement of 4X4. But returning to slower speeds it doesn't usually return to full time mode. So they have it flashing the engine light and you have to manually reset the switch to auto, wait till it stops flashing, then you can switch to full time 4X4 again as long as you stay under 35. I always turn mine back to auto when I get above 25.

Thank you for the info :) I never changed the fluid yet, bought the used truck a few months ago, checked the stick while engine was cold, did not appear low, I did drive 4x4 30-60 mph only because the visor sticker said don't exceed 60mph in 4x4 mode.