02 trailblazer, accessory wiring for ignition

2002 Trailblazer LTZ
I am installing a circuit board that will modify the front O2 sensor signal. It requires a 12v power supply. I want it to be connected so it will be on and off with the ignition switch. I currently have pulled my wires through the firewall, but now I am not sure what the best way is to make this connection.

Also, I have yet to track down the front O2 signal wire that is after the sensor connector. I have to intercept the signal wire on the way to the computer.

This is my first run at doing anything like this and there are about a million ways to screw it up. Can anyone help me with this?

You want to tap in to the ORANGE wire under the dash by the steering column coming off the ignition switch. What are you trying to accomplish here by bypassing this wire ?

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Jeff
Velocity Custom Home Theater
Mobile Audio/Video Specialist
Morden, Manitoba CANADA

Thanks for your reply. I just realized that I posted in the wrong forum.

My circuit board is called an EFIE (electronic fuel injection enhancer). It can be adjusted to enhance the O2 sensor signal to get the computer to run a leaner air/fuel mix. I will be using this with a hydrogen fuel supplement system. When running the hydrogen system the O2 sensor will send a lower signal to the computer that would make the computer compensate with a richer air/fuel mix which I want to avoid. what comes from the O2 sensor goes into the EFIE and what comes out goes to the computer.

I only want the EFIE powered when the engine is running. I should be able to locate the ORANGE wire under the dash. I'll just splice off of it. If I'm off base here please let me know.

I want to make sure I find the right signal wire coming from the O2 connector.

Jeff
I'm now connected to the signal wire from the O2 sensor. Thought I would replace the old O2 (146,000 miles)while I was at it. That's where the trouble began. I worked it over for 4 hours with penetrating oil, still no luck. She is stuck, she is stuck bad. I'm letting it work over night. Afraid to put to much heat on it with all the oil on the manifold. Tomorrow will be a better day.

I did get the check engine soon light cleared by disconnecting the ground from the battery while I was futzing with the rest of this.

Back to the ORANGE wire at the steering column. This steering column harness terminates at the base of the dash into a junction. There is one larger ORANGE wire going into the junction (about 3/32 in dia. whereas the other orange wires are maybe in the 18 ga and smaller range.) From the junction box some of the wires terminate in a module mounted on the backside of the lower dash cover plate (just above the pedals). Another group of wires from the junction head towards the firewall. On the way to the firewall there is a loop out of the harness consisting of a small ga light blue wire, a dark blue wire and the large ORANGE wire. There is a tag wrapped around the loop identifying the colored wires. The ORANGE wire (about 3/32 in dia.) is tagged battery. Visually it traces back to the ORANGE wire in the steering column harness.

Have I found your ORANGE wire?

Remember, I want the EFIE to be on when the engine is running and to be off when the engine is off. The Trailblazer has a delay built in to turn off the radio when the doors open after the engine has been shut off (if that makes a difference).

Here's a thought. The O2 (4 wire sensor) has (2) heater wires (white) I believe conected to 12V. Is it an option to tap into one of the heater wires for my power source? The EFIE only needs to be on when the O2 is powered. The draw from the EFIE is Mice nuts. I don't think it would cause any problem.

Vehicle down, waiting your reply.

The orange wire is the ACCESSORY wire for the vehicle. It will have 12 volts when the key is in the ACCESSORY & ON positions and will drop out during start. This circuit is not connected to the RAP system. The ORANGE wire will be coming down along side the steering column and terminates into that junction box you mentioned. To the right of it is the RED / WHITE constant power wire and above it is the YELLOW starter wire. It is the first larger gauge wire on the bottom row from the left.

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Jeff
Velocity Custom Home Theater
Mobile Audio/Video Specialist
Morden, Manitoba CANADA

BTW, are you using the proper wrench for the O2 sensor ? There are specialty
wrenches that are used to specifically remove 02 sensors ?

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Jeff
Velocity Custom Home Theater
Mobile Audio/Video Specialist
Morden, Manitoba CANADA

Turns out that the ORANGE wire in the loop I mentioned is there for an aux, but is constant on (ignition on or off)12v. I'll leave it alone.

Your ORANGE wire is exactly where you said it should be.

YOU DA MAN!

I'll tap into it on the key side of that junction box and be done with it.

This is awesome! Thanks for your "spot on" direction.

FYI, the split socket for the O2 still spreads when turned on the old sensor. I had cut the wires and used an extended 7/8 standard socket. Then she came out. Threads were good and the new O2 is working as it should.

hay let us know how good that thing works at 4.00 a gallon it would be grate to find a thing that will help up save money.

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i kant spel