2007 columbia electrical problems

Hello guys ,I have a 2007 Columbia, the truck drives fine for two days then oil pressure gauge drops,water temp gauge drops as well and fan clutch goes on together with check engine light not to mention a massive power loss the truck won go over 15 MPH and then starts working normal .I replaced both main wiring harness and the one that goes from batteries to ECM.I really need help I don't know what to do anymore .thanks in advance .

 

The starter cables come from the harness that plugs into the firewall to the ECM and that harness has a plug that runs the wiring to the batteries all that has been checked all grounds to the ECM are tight and secure both main sensors harness and main harnesses that plugs into computer 860.00 buck for the two have been replaced this truck is driving me crazy.even at idle runs for hours perfectly and all of the sudden fan clutch goes on I run to see the dash and guess what check engine light is on and everything else that I mentioned happens at the same time.Thanks in advance for your help .

 

I was thinking of that, im going to check when I get to the yard since this was a company truck ,I have a volvo as well and it was doing something similar but no loss of power and in fact was that wiring that you just mentioned,I really appreciate you took the time to help me .ill keep you posted and have a good day

 

Hey qualitytruck thanks for your lead in fact was the qualcom
Wiring what was causing the problem incredible how that harness
Would power down the truck .I was going nuts.Thanks again