Dash code lights keep coming on

I have a 2006. It has had a problem with the brake lights, if it gets below 60 degrees they come on. I bungy cord the brake to keep it taught so that they don't come on. I forgot to one night and it got cold. The next morning the car was dead. My ex put in a new battery without knowing what he was doing. I ended up taking it to a mechanic where the wire harness and main relay were replaced. No the "triangle of death" light, oil pressure light and check engine light are on. The code reader will reset them but they come back on after a while. Any suggestions on what I can do?