Confused warning light

[Jack Douce]

I am totally confused.Day 1 engine diagnostics light on when engine running no message in multi function display. Day 2 diagnostics light still on and now a message on multi function display L/H rear tail light/brake/reversing light. Did a visual check and the reversing light not working,changed faulty bulb all lights appear To Be working visual check,engine diagnostics light now goes off when engine running. Day 3 diagnostics light still goes out when engine running but message on multi function display L/H read tail/brake light. Day 4 changed the other 2 rear bulbs no messages in multi function display but engine diagnostics light back on when engine running. Please help am totally confused.