Ok rather than make separate threads for each problem I'm going to slap them all in here. First let me describe the car. '96 EK Hatch B18C Block with B16 PR3-2 Head '00 Si Transmission Skunk2 Intake Manifold Skunk2 Cam Gears JG Edlebrock 65mm Throttle Body Short Ram CAI with K&N Filter RC 550cc Fuel Injectors AEM Fuel Rail/Regulator MSD Spark Plug Wires DC Sports 4-2-1 Race Header - No Cat A'pexi WS2 Exhaust OBD1 P28 ECU w/Hondata S100 First problem is the engine harness. It is the original '96 DX non V-Tec harness. I'm not sure if the engine was from an OBD1 car or an OBD2 car. The head and transmission seem to be from a 99-00 Si. The Block has a B18C stamp on it. The transmission for sure is from a 2000 Si. The head has a PR3-2 stamp on it. The current ECU is a P28 with a OBD2 to OBD1 conversion harness adapter plugged in. So what do I classify as, OBD1 or OBD2? I'm just confused since I am starting to feel like the car is half OBD1 and half OBD2 and wondering what is and isn't compatible with the OBD1 ECU. Second problem is the O2 sensor. The car has had a CEL from the beginning. I checked it and I get Code: 41 Primary oxygen sensor heater. So I bought a universal Bosch sensor and wired it up but the code is still there. I wired it up as so: the 2 OE black wires (heater) to the 2 Bosch white wires, the OE white wire (signal) to the Bosch black wire, the OE green wire (signal ground) to the Bosch gray wire. Hopefully I got it right. I was told it doesn't matter which way the heater wires are arranged as long as the colors match. The car runs the same whether the sensor is plugged in or not so I'm guessing its not working. The engine harness has two plugs for the front O2 and the rear O2, but I'm only using the front O2 plug since OBD1 ECU doesn't use a rear O2 right? Third problem is the Speedometer isn't working. I check fuses and all are good. I checked the wires that run to the Vehicle Speed Sensor and they seem fine. I am not sure if the sensor itself is dead. Wouldn't I get a code for that as well? I guess I'll just swap out the sensor and start there. Fourth, (I know its getting long,) I'm wondering if I should just swap out the engine harness for a 96-98 EX harness or a 99-00 Si harness since I feel like the previous owner didn't do too good a job on the harness. Almost every single sensor seems to have been spliced into the original harness. Just yesterday the car wouldn't start since a wire that connects to one of the fuel injectors came loose. took me about an hour to find the problem. OR am I able to swap in a 92-95 civic OBD1 harness? I'm not sure on this since like I said before I'm not sure if I can say the engine is OBD1 or OBD2. How can I check? This car is all Frankensteined! Oh and another thing is there is a Injector Resistor Box installed. Do I need that? I guess I do, but can I swap injectors to get rid of it? The box is just dangling behind the head and looks ugly. Just another thing to clean out of the way. Hopefully I didn't confuse everyone with all my problems. Please if anyone has any input on anything I listed, chime in. I need all the help I can get.