30AndSeven

Hey all, after several days on this issue, i'm completely stumped. I own a 2000 civic EX (D16Y8). I am getting both error codes PO117 and PO118 at the same time (ECT sensor circuit high input and ECT sensor circuit low input!) The CEL comes on immediately after power on with key on engine off.

I have already bought/installed new sensor, connector harness, and wiring all the way back to the ECU, as well as topped off the coolant. The resistance on the circuit cold is about 2.9k ohms, which is the correct reading.

ANY help with this would be hugely appreciated. I'm about to start throwing stuff at walls here...

A few questions that could maybe help (keep in mind I am pretty inexperienced with electronics; some of these may be dumb questions, but it would help to have them explained to me):

Most of the info online on ECT sensor says they operate off a 5v reference wire, but the wiring schematic in Haynes has the reference wire coming out of a 12v ground from the ECU (Have tested the voltage, it is at 12). Is this correct? Do our ECT sensors work off a 12v reference rather than a 5v one?

The voltage doesn't change after going through the ECT, despite the fact that I repeatedly checked the resistance, and it is correct. Have I discovered a wrinkle in the laws of physics? or do I just not understand them...? What should the voltage reading be at the signal wire (after the 12v reference has passed through the ECT)?

Thanks in advance for any help!