D4 flashing call will crank but won’t start

Hello, if the D4 is flashing while driving, it indicates a problem electronically with the automatic transmission. Testing is needed with that system to find out what is happening. As far as not starting, that's due to some other concern - also unknown as to root cause. Testing must be performed in this system as well to find out what's happening. Use this link to find some shops near you that can help with your concern: www.repairpal.com/repair-shops