EF.Hatch

My brother bought a civic and it has a code 10 that just wont go away. I've tried:

1)test the wires, came out good (voltage and resistance)
2)new sensor, did nothing
3) lead new wires to ecu, nothing
4) swapped ECU 4 times with known good ecus, nothing
5) engine swapped with a stock replacement, still there

I'm at my end as well as my brother. I can't think of anything else to do and we don't want to burn these valves and rings like the other engine that was in it. The car is an auto 1.5L civic hatch 1992 if it matters.

Any help is appreciated. On a side note is it possible to chip the ecu so it doesn't use the IAT, this should eliminate the code 10.

D.T.P

Got a multimeter, with car off and battery disconnected, check for resistance in ohm scale. It could be a coroded or cut wire somewhere. Also is the plug/contacts rusty or water damaged?

EF.Hatch

The oem plug is corroded greenish color. The part that confuses me is when I did a rewire with a newer clean plug the light stayed on. I ohm tested the sensor and it came out good. If I'm supposed to test the wire how should I test it and what should I look at as readings go.