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Discussion Starter #1
i swapped a d16y8 into my 98 civic hatch. i converted to obd1, but would not pass inspection. i will have to hook up the secondary o2 sensor and run obd2. i thought about hooking it right into the ecu. i looked up for all the pinouts of the ecu and kinda have an idea where three wires go, but i dont know where the fourth wire goes. has anyone ever done this? will this work? please help. thanks
 

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You can't wire a second o2 sensor into an OBDI ecu directly to the best of my knowledge. Plus, why run a second o2 on an OBDI? Just get your CEL off, and get smogged.
 

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what state are you in?

just toss the obd-2 ecu in for the test and then switch back. its only every other year.
 

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Discussion Starter #4
i live in nc. they use the obd 2 port to scan the ecu and it didnt read the obd1. so i have to put the obd2 ecu back in. i am only running one o2 sensor so i have a cel when i use the obd2 ecu. they dont do smog here they just check your ecu to make sure it isnt throwing any codes for 96 and up model cars. i have an d16y8 engine harness. i thought about getting the under dash harness so i can just plug in the secondary o2 sensor, but that just seem like too much work. so i thought maybe i can just run the secondary o2 sensor right into the ecu. like i said before. (4-wire o2 sensor) i figured out where three wires go to, but i dont know where the fourth wire goes into the ecu. thanks
 

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Your just going to have to toss in the obd2 ecu when you get checked and make sure the second o2 is plugged in. Then after they check it just switch back to what you had. And wiring the second o2 sensor to the obd1 ecu will not make it read from the obd2 diagnostic plug...
 

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Discussion Starter #8
i found the pinouts of the ecu. i only found where three goes to but i cant figure where the fourth goes to. 1)a-5 second o2 heat control (black and white wire) 2)d-13 second o2 sensor ground (green and black wire) 3) second o2 sensor-2 (white and red wire). i cant just plug it in because i have an 98 cx hatchback. i swapped in an ex engine with an ex harness. which have only one o2 sensor plug. i found out i would have to get an ex under dash harness, because the second o2 plugs into that harness. i didnt want to go through the hassle of pulling off my dash so i just thought i could wire the second o2 into my ecu. thanks
 

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Discussion Starter #9
on the secondary o2 plug, there is a white and red wire. a black and white with a grey ring on the wire, a green wire, and another black and white without the grey rings on the wire. i figured out where the first three wires goes. i just cant figure out where the last wire, the black and white wire without the grey rings, goes to.
 

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on the secondary o2 plug, there is a white and red wire. a black and white with a grey ring on the wire, a green wire, and another black and white without the grey rings on the wire. i figured out where the first three wires goes. i just cant figure out where the last wire, the black and white wire without the grey rings, goes to.
It should go to a 12v source, normally from fuse #15 in the under dash fuse box. You can just splice it into the primary o2 heater power wire if you want.
 
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