My check engine light is on, could it be because it's not reading my coolant temperature?

While I was driving I hit a bump and my check engine light came on, which made me think a wire had come loose. When I looked closer I realized my dash was reading; Coolant:--
It stayed this way for roughly a month, then one day my check engine light went off and my coolant reading was displaying a temperature (can't recall the number). The next time I turned on my car the check engine light was back on and coolant was no longer displaying a temperature. Any thoughts?