i installed a air/fuel ratio gauge,,but it reading a constant rich on the gauge...grounded/power souce was hooked up correctly,,but i don't think i tapped into the o2 system properly,,what wire do i tap in to??
thanks
-Jason

 

You are only going to be able to read one bank or the other because you have to tap on of the O2 sensor wires. Both wires input into the back of the PCM, I beieve one is purple and the other is purple/white. Your going to need a schematic of the wires going into the back of the PCM to be sure. I'll see if I can come up with something and post back.

 

I used the purple wire with the white stripe. It's the wire for the drivers side O2. It's located in the wire harness that runs across the rear of the engine. Just splice into it and you'll be good to go.

 

I just got a schematic, being a tech at a Chevy store and having access to gmservice.com comes in handy .

In the clear/gray connector at the PCM you can tap the purple/wht wire at pin 20 (bank 1 LF), purple/wht at pin 18 (bank 1 LR), purple wire at pin 8 (bank 2 RF), or the purple wire at pin 4 (bank 2 RR). Hope that helps.

 

You can run the pin C8 and pin C20 wires to a single-pole/double-throw (SPDT) switch, that will allow you to select either left or right pre-cat sensor, and switch between them.

After you are all done, you will probably be disappointed with the results... a psychedelic light show in closed loop/part throttle, and almost meaningless "rich" indications at WOT/PE mode.

If you've got a constant "rich" reading, there's a good chance you tapped into the wrong wire and are feeding more than +1V to the gauge.
Why would you want to tap into the after-cat sensors (pins 4 and 18)?

 

Wouldn't want to, I just put those up there to make sure he got the right ones.