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Use O2 heater wires to power wideband?

8K views 16 replies 7 participants last post by  BISHILVR 
#1 ·
Ive got an LC-2 that ill be wiring up soon. Ill be using the wideband and the narrowband SIM feeding the ECU at the same time. Now since i will be eliminating the stock O2, the heater wires will be left open and will set off a CEL. I was going to use a 30-ohm resistor to simulate the heater and avoid the CEL, but now im thinking cant i just use the heater wires to power up the wideband itself? And since the ground is coming from the ECU, its already the isolated ground that should be used for the widebands anyway. Anything wrong with doing this?
 
#2 ·
The heater wires might be the right voltage, but they run an awful lot of current, which might be too much for your wideband and narrowband. I forget how much current, (I think it's 1 amp), but most electronic type devices run somewhere in a mA range.

I know when I eliminated my stock 02 for a wideband I tried to fool the ECU with a 12 ohm / 12 Watt resistor (huge resistor BTW) and it got wicked hot ... too hot, it scared me and I undid it. Most resistors are sold in a 1/2 watt to 1 watt range so whatever you do, make sue you order the right stuff so you don't set anything on fire.
 
#4 · (Edited)
it may flow 1A for the heater circuit, but it depends on the resistance load of the wideband itself to determine what the current flow would be. The 12 ohm resistor you used and using ohms law, will be 14.4V divided by 12 ohms = 1.2A. I would use as high-ohm a resistor as i can get away with to minimize the amount of current and not get a CEL. I found on a Mazda forum that they use a 30-ohm resistor which would flow 0.48A and should be much cooler on the resistor

BISHILVR said:
I dont see why you couldnt use the rear O2 heater wires to power the wideband unit if you wanted to, but the fact that the wideband unit itself powers the wideband sensor
Its the front O2 that ill be eliminating /replacing to run the narrowband sim, so its the front that leave the void and cause my heater CEL

I completely forgot that the wideband itself also powers the heater also, which would draw even more current than the heater by itself. I guess the best thing to do is power up the wideband with the sensor attached for an actual current measurement and see how much current it demands
 
#3 ·
I used to just leave the stock rear O2 zip tied under the body of the car to keep the light off, then I went flashable ecu and just wrote the code out to not check for the rear O2. I dont see why you couldnt use the rear O2 heater wires to power the wideband unit if you wanted to, but the fact that the wideband unit itself powers the wideband sensor (and has to), I doubt that you would get rid of the light due to the difference in resistance between a direct connection to an O2 sensor heater circuit and the input impedance of the O2 controller.
 
#6 ·
Yes, which is the whole reason im looking to hook something up to fill its spot and avoid the CEL.

The narrowband sim from the Innovate will feed the original O2 signal, and im looking for something for the heater wires to power up, so i figures why not the wideband itself?
 
#8 ·
You can laugh if you want, but I work w/ electronics for a living. Most small electronics devices w/ any kinda of microprocessing ability tend to run around "X" voltage at a mA level. Run too much current through something and things can get hot pretty quick.
 
#9 ·
OK, this past weekend i ran some tests comparing the current flow on my OEM O2 sensor heater wires vs. the power wires on an Innovate wideband with its oxygen sensor connected.

Tests are taken at 12.49V with engine NOT running.

OEM 2G Oxygen sensor:
.85A initially cold, and then settles to .57A after heater is fully warmed

Innovate wideband:
1.86A initially cold, and then settles to .75A after heater is fully warmed

Im not too concerned about it demanding .75A seeing that the ECU handles .85A just fine during cold with my OEM sensor, but its the initial 1.86A on the wideband that worries me. I dont know if the ECU supplies power through a relay or if its going through any output transistors, and id be afraid to blow the ECU. Any thoughts or suggestions?
 
#10 ·
The heater power is likely powered through the mfi relay like it is on the 1g, I cant see any reason for it to be powered through the ecu which already generates enough internal heat as it is.
 
#13 ·
I'm glad you started this thread, OP. I plan to do the same thing with my MTX-L, and was wondering how to deal with possible check engine lights. However I have a 1G and don't ever plan to live in a place where emissions are checked. I'll just disable the CEL. :p
 
#14 ·
Just a FYI... I decided to give this a shot, and it worked but it doesnt work :)

It worked to power up the wideband and satisfy the CEL light as planned. However i found that above 3K RPMs the heater circuit cuts out. The ECU figures that the heater is no longer needed at that point and cuts the power going to it. So in the end, I left the OEM O2 sensor connected and just strapped it aside. It was a good learning if anything.
 
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