In Colorado and going up and easy trail started getting a little rough as in The road but not bad and my check engine light comes on. First time in 25,000 miles I’ve had a check engine light. The code is 12. RPM Signal - no NE OR G1 OR G2 Code sent to ECM within 2 seconds after cranking the engine. Trouble area Distributor Circuit, Distributor, Starter Signal CircUIT, ECM. The behavior is hesitation when the road gets rough.I then drove it on the highway no code even under strain going up steep grades but if I put my right tire on the bumpy shoulder the light comes right on. I can sit and rev it and no signal. Also the CEL will turn off after a period of time. Got to be something loose. Any ideas. Help sure would be appreciated.