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Anyone have a wiring diagram for a '91?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by 91K5, Oct 27, 2001.

  1. 91K5

    91K5 1/2 ton status

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    Anyone have a wiring diagram for a \'91?

    I'm trying to figure out which wire is the signal from the O2 sensor so that I can get my air/fuel gauge installed... The wire from the O2 sensor is gray, and tracing the wire as far as I can it goes into a larger loom, but I cant trace it part of the way because it goes inbetween the firewall and back of the motor. The part of the loom I can get to does have 1 grey wire in it, but I'm not for sure that this is the same wire. If anyone knows what color the wire should be, that runs back to the computer, please let me know. Thanks.
     
  2. Sledge

    Sledge Registered Member

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    Re: o2 sensor wiring

    At the ECM connectors might be the easiest. There are 2 connectors at the ECM, the O2 sensor is on the larger 32-pin connector. The connector is keyed, the a couple of raised peices on one side, that's the side that has the O2 signal. The wire you're looking for is purple, seven in from the end, and should be next to a tan wire (that's the 02 signal ground wire).

    I hope that means something to you, more than if I just said D7 anyway. :)

    Might try disconnecting at the ECM and the O2 sensor and doing a quick check with an ohm meter or test light before splicing. Electrical tape looks messy there when you grab the wrong wire. Guess how I know... :)

    Sledge
     
  3. Sledge

    Sledge Registered Member

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    Re: o2 sensor wiring

    Just reread your post and since it sounds like your O2 signal wire may be "grey" not "pink" like I'd expect, you've got me wondering. I did find a TBI connector pinout on-line for you though...

    ftp://ftp.diy-efi.org/pub/gmecm/manuals/1227747/747ecm1.jpg

    Hope you can resolve stuff.
     
  4. TheGeneral

    TheGeneral 1/2 ton status

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    Re: o2 sensor wiring

    If you don't figure it out, let me know, I have a GM electric wiring manual for an 89-91 K5s. I have to find the right diagram as it is a book of 200 pages full of wiring blueprints.

    If you ain't hurt, you ain't playin' hard enough.

    The General
     
  5. 91K5

    91K5 1/2 ton status

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    Re: o2 sensor wiring

    Well I hooked up the Air/Fuel gauge to the Purple wire, wire that goes to D7 on the ECM. The gauge seems like it works OK when idle, but when driving it just goes crazy, it goes from lean to rich, back and forth over and over, and sometimes it simply doesnt show anything. I looked at that ECM pinout, and it shows that this is the correct pin to connect to. I just replaced the O2 sensor last year, so it should be good. Do you guys think that I might need to upgrade to a 3 wire O2 sensor? Since the O2 sensor cant send out accurate signals until it reaches 600 degrees, maybe it's not getting warm enough or something. If you guys have any more ideas let me know. Thanks!
     

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