O2 Sensor Woes. HELP!!!!
 

94 Silverado K2500HD, 5.7, 4L80E


Supposed to be a Purple Wire from Computer D7 that is direct to Upstream O2 Sensor. Not there none on mine Can someone tell me how I can install a new wire so I can hook up my O2 Sensor and make my truck stop running so rich?

Are you saying there is nothing connected to the sensor now?

yeah, what do you mean? no connector/no wires or the wires present are the wrong colour? pics help.

Have you tried replacing that upstream O2 sensor?
Have you tried reading your truck for codes?
Reading with a LIVE CODE reader will give you a more accurate reading on why your truck is running rich

Keep us updated

O2 Sensor/Help
 

Ok folks, there seems to be some confusion as to my problem with the O2 Sensor. I believe that I have figured it out, but will definitely let you all know when I do.
In the meantime, I will try my best to explain things better so that everyone can understand more fully.


I bought this truck for $50.00. 94 Silverado K2500HD, 5.7, 4L80E.
Next day I pulled the tired engine out of it, and installed a 23000 mile 5.7 that I had in my garage. I also istalled a "rebuilt" 4L80E, and a rebuilt Transfer Case.
Next I found that nearly every wire going to the Trans., and to the Actuater on the front axle had been drenched with oil and had been hot- because they were all brittle. Snapped like a twig between my fingers.
I tried locating a doner for the Harness, but no luck. So- I bought the wire and commenced to splicing and soldering and heat shrinking each and every wire.
The Y Pipe that was with the truck had the O2 Sensor Bung in it, but no Sensor. I bought a new Sensor and it would just keep popping out when I tried to tighten it. Got a O2 Thread Chaser and seemed to work, But Sensor would'nt tighten. So- I pulled the Y Pipe, drilled a new hole and welded a new bung, as well as welding the old one closed. Reinstalled everything including the new (One Wire) Sensor, and this is when I found that there was no Male Connector. Went searching, but could find nothing.


So, with the help from people in these forums I finally got a schematic of the wiring designation for the O2 Sensor. It is actually, A10 (Purple) on the ECM Connector, A10 goes directly to the O2 Sensor with no connections in between.

I haven't had the time to trace that wire yet. There are actually (3) Purple wires in this connector. One goes to Brake switch, One goes to Transmission, and the other Is My O2 Sensor. So- I have to unbolt the plug/connector and find A10, and follow that wire to see where it ends (which I believe will be cut off somewhere in the Harness).


I'm not sure where the D7 I was told it is would be located, because on my specific Connector at the ECM there is no D7.


I cant take pictures. My phone is my only camera and it's not very focused and couldn't make them out.


So, I believe that I have the information I need with this schematic showing me A10 being the O2 Sensor. The Haynes manual shows the same thing, just not the actual number/letter on the connector. I just need to find the time to get to it. Been working on so many other things past cpuple days that I haven't had the time.




If there is anyone out there that disagrees with my findings concerning this O2 Sensor, please speak up and show me because I hate doing things three different ways from Sunday!


Oh, I checked the VIN. This is NOT a California truck.




Thanks for all the help everyone. I am seriously learning sooooo much from you guys. I have never had to deal with wiring in my life. Never knew how to test, nothing! Oh, I HAVE NEVER USED A SCANNER. DONT HAVE ONE OR KNOW ANYONE THAT DOES. I DONT HAVE THE MONEY TO BUY ONE (YET). SO READING THE CODES IS OUT OF REACH FOR ME AT THE MOMENT. But- information I have is that Having no pre-heated O2 Sensor will make the engine run rich, especially on cold starts (which is what mine is doing).

When I was looking on line for info on your O2 sensor I came across some info on changing the single wire sensor to a heated sensor. I'll look back and see if I can find it and if so will post it here.

Here some info on converting to a heated O2 sensor.
install of 3 wire (heated) oxygen sensor - Third Generation F-Body Message Boards

This diagram shows it as D7 too.
http://repairguide.autozone.com/znet...3f80231a10.gif

Here is a pinout of the ECM connectors D7 is in the 32 pin connector.
http://www.chevytalk.org/fusionbb/fb...49-747ecm1.jpg

Hope this helps

Everything you've said sounds pretty spot on to me, I don't see any reason to not continue with your wiring quest. I converted my 91 firebird's 02 sensor over to a heated one. I personally haven't noticed any change. These two vehicles actually have the same engine and extremely similar engine management systems.

The D-7 direct to O2 Sensor in these schematics is for 94 Chevy Truck w/MANUAL TRANSMISSION.

MY TRUCK IS AUTOMATIC 4L80E


Also, I noticed that A-11 is Sensor Ground, while D-7 is Sensor Signal.


In the Chilton Manual it shows in the schematic as A-11, Purple Wire to Sensor, but doesn't state Ground or Signal?


On single wire hook up, am I looking for Signal or Ground?

add to the confusion
 

the diagram I have from Mitchell on demand shows a-11 as unused. a10 is the signal wire labelled oxygen sensor high ppl wire circuit 412.
the o2 circuit low is the grd... wire a12 circuit 413 tan wire.


be wary of Chilton wiring diagrams; does it say its for the 5.7L engine