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Discussion Starter · #1 ·
Hey guys,

I'm just trying to wrap up my first B swap (http://crxcommunity.com/viewtopic.php?t=5101) and have a question regarding the oxygen sensor. I have a B16A2 from a 99 Si in my 89 Si. I am using the stock A6 engine harness with a OBD1 conversion harness to run OBD1. I believe I am supposed to run a 4-wire OBD1 oxygen sensor, but this does no plug directly into the A6 harness plug. I believe I have to wire the extra wires to the ECU (which I believe the conversion harness provides but I need to double check). Does anyone that has done this before have any input for doing this? Any diagrams showing what each wire does on the oxygen sensors so I know what goes to what? I'd like to make another jumper harness so I don't have to hack the engine the harness, but we'll see what's required. Any input is appreciate.

Thanks.
 

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Here are the 4 wires:

- O2 signal (the 1 wire from OBD0)
- O2 Heater (If I remember it's...A8, but don't take that to heart)
- 12V
- Ground

I did my own harness myself, so here's how I did it.

I wired in the ground to the thermostat, I took a 12V from a sensor (wired it into my stock harness), took my O2 signal and deloomed it, and reloomed it to the back of the engine and then I ran my O2 Heater from the ECU. Worked perfect.
 

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If youa re using a chipped ecu, you can just use the one wire and turn off the 02 heater.

If not, yes you have to wire it up. the 2 identical colored wires on the sensor are heater +12v/ground. They can be wired interchangeably. Pin D14 is the power for the heater. and pin A6 is the senor signal. I think, that could be the other way around, I have no way of checking right now.

They other 2 wires are sensor signal, and sensor ground. Sensor ground is D21, or somewhere like the thermostat housing. Make sure to ground the heater wire seperately from the signal ground.
 

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Discussion Starter · #5 ·
Thanks for the responses guys! Forgot to mention, I do have a chipped ECU for the engine/car and I also have both O2 sensors. I don't know how much I rely on the ECU as this stuff came from a crappy seller. I guess what I'll do before hacking into everything is just try the stock O2 sensor and see what it does. If it throws a code or something I know I'll have to use the 4-wire sensor. Good idea?
 

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Its me DUB said:
ludesrv said:
I would just do it now if I were you. It sucks starting up for the first time with the CEL on.
With me doing everything...I'm sure a CEL on start-up will be difficult to avoid anyway! :lol:

Good call though. It's getting warm...I'll work on this this week. Thanks for the info guys.
If you do everything right you shouldn't get it and VTEC should work on the mayden voyage. If you get the CEL just PM me. I've cleared a good bit of codes in my time.
 

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ludesrv said:
I wired in the ground to the thermostat, I took a 12V from a sensor (wired it into my stock harness)
FYI, white = O2 signal, green = O2 ground, black x2 = heater.
You want to connect the O2 ground to the sensor ground, not the thermostat ground. The sensor ground (grn/yel IIRC) runs back through the ECU before being grounded to help filter out electrical noise. It's shared by the coolant temp sensor, air temp sensor and TPS. The regular thermostat ground may work, but will probably result in a dirtier signal to the ECU.
The O2 heater gets 12v+ on one lead and ECU controlled ground on the other. On OBD-1 cars, the heater is on the same power supply as the EACV, so tap in there (blk/yel).
 
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