I just replaced the engine wiring harness on my 99 accord 2.3 vtec 175k miles and the p1166 and p1167 codes have popped up. I replaced both o2 sensors 25,000 miles ago so i believe that the o2 sensors are still ok. I have rechecked all of the harness connections around the intake manifold and they are all plugged in all the way, i have also rechecked the connections to the engine computer in the passenger area. If anyone knows what to do next i would appreciate the help. Thanks...

 

p1166 is a heater circiut dtc. my first step would be to check the fuse(yes, there is a fuse for the heater circuit). The fuse is Fuse number 6 in the passenger side under-dash fusebox. it will be labeled LAF HEATER. try that, if that doesn't work I can try to help you diag the problem further

 

Ohm the heater circuits, this will test the wires and the heater. Also make sure that the old wires match the new wires for your swap.