Engine light on READING OIL PRESSURE 19 PSI - HELP!

OK I was playing in the car all day on the audio system. I had the negative battery terminal off and back on twice, and I removed the factory amplifier and the 2 black plastic harnesses that attach to the black part on the amp (part reads Siemens).

I put the black part (Siemens) back under the dash, with the harnesses back in place.

Since then I am getting the Engine light on during start, and if I am reading the system correctly (it goes like this: DOOR AJAR, then it is showing OIL PRESSURE 19 PSI (then when you hit the gas the oil pressure reading increases) and then it scrolls to giving the reading of the oil temp as well. I assume these are Codes saying probs possibly with the OIL Pressure or Temp?

Car was running a little hot I though, last night it was running 225 deg after like 5 min of idle. Then it came down to 212-214 after driving a short distance...

Did I mess something up by removing the 2 wire harnesses attached to the black device on the amp (by the way this item I do not think had any connection to the audio as far as I know it was simply attacched to the amp by 2 screws). Or is this a problem that will need to be addressed by the dealer?