Hello welcome to just answer I'm Master Tech and will be able to assist you today.
this is most likely caused by a faulty 3rd or 4th pressure clutch switch in the transmission. but to confirm this the codes on the transmission need to be checked.
How urgent is this problem if it is a faulty pressure clutch switch? Is it safe to drive a 400 mile trip if the light only comes on so intermittently? No gauges on the dashboard look irregular or abnormal. We suspect this problem has been caused by using D2, the lower gear, going down a mountain near our home. We have stopped using that gear altogether since the D light has been blinking and it has not blinked since. The light came on 4 different times during our last trip and each time we stopped driving for less than 2 minutes, turned off the engine, and then were able to drive long distances before it came on again.
Honestly I think it will be ok to continue, but make sure the fluid is correct and the condition is red.
im sure that if you went to the local parts store like auto zone or advanced auto parts they can look up the code and then clear it and it might be ok for a while but needs to be looked at.
just be easy on the transmission and keep it in D5 only
did you have any more question that I may answer for you on this subject ?