1990 Suburban o2 sensors

Discussion in 'GM Powertrain' started by Estam, Feb 18, 2008.

  1. Estam

    Estam New Member

    Just purchased 1990 Suburban with a 454 and last owner installed headers. Don't see any o2 sensors so maybe they haven't been installed. Can anyone point me to where the computer is and where the o2 sensor harness could be located, and would there be two o2 sensors on that year? Many thanks...
  2. Crawdaddy

    Crawdaddy All hail the Mad King!! Staff Member 5+ Years 1000 Posts Platinum Contributor

    On my 91 Suburban 1500 with the 350, there is one O2 sensor. It's located on the drivers side downpipe to the Y-pipe. Oddly enough, this mean's it's only monitoring the driver side bank of cylinders. It's a 1-wire O2 sensor. Hope this helps you...
  3. Estam

    Estam New Member

    Yes, thanks, mines a 2500 with 454 and was wondering if it had one or two sensors. I'll have to go digging to find any wires. Would be nice to know where roughly to look, maybe off the fire wall. Also like to know where the computer is on this model.
  4. Tom Evans

    Tom Evans Rockstar 100 Posts

    I got my 1990 GMC Manuals out and they show that you have only one sensor with the 454 engine. There is a single PURPLE wire going to the sensor with a connector about 6"-8" from the sensor itself. As best I can tell, the sensor is mounted in the left exhaust manifold. If the previous owner replaced the manifolds with headers, he had to find some place to mount the single sensor. I can't think of a way to "trick" the computer to work properly without having a working sensor installed.

    I no longer have my 1990, so I can't simply look at the sensor and tell you how the wiring harness breaks out, but I would think it came around the back of the engine.

    Also, going from memory, the computer is located above the heater in the passenger compartment. You gain access to it by removing the glove compartment.

    Good luck, that oxygen sensor has to be somewhere down there. Either that or the Check Engine Light has been removed.
    Last edited: Feb 22, 2008

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