seems to be not shifting into 1st gear

I have a 2000 Honda crv that seems to be not shifting in to 1st gear at times did it once 4 days ago and then ran like a top the next day 3rd day did it again and the engine light is also on some one suggested it may be the TP sensor...Thank you and hopeful - Great site!

At times it does not shift into first gear but if you keep your foot on the pedal it will work.