DIY heated Oxygen sensor

Discussion in 'Performance & Fuel' started by TrailLeadr, Sep 19, 2007.

  1. TrailLeadr

    TrailLeadr Epic Member 5+ Years 1000 Posts

    My suburban takes about 5-7 min, depending on outside temps to idle down after it's started from an extended sit.

    Nothing makes me cringe more than watching my rpm's hover around 1200-1500 while the engine warms up. Especially with the gas prices the way they are today.

    What I'm doing is installing a heated O2 sensor in place of my non-heated one.
    NOTE: This write up is going to have specifics for a 1993 suburban. Other years MAY be similar, and possibly will be identical. This walk thru is meant as a guide on how to convert your non-heated O2 sensor to a heated one. You may have to do some independent thinking to get the job done for your application, if it is different from mine. Sorry, I just can't cover all makes and models.

    So, on to the good part.

    For starters you'll want to obtain a heated oxygen sensor. The method I used was to put the parts guy to work. Had him lookup the sensor for the 96 suburban with the 7.4L engine (the pre-cat sensor), and compared it to the sensor for the 93 suburban with the 7.4L
    The sensors were identical in thread, and diameter.
    The sensor I got is a Bosch #15732, and is regarded as a generic heated sensor.
    The great thing about this sensor is that it comes with it's own connector, so you can wire it up to just about any vehicle.

    Contents of box for Bosch heated oxygen sensor shown below:

    Next you'll want to obtain a 30Amp automotive relay. You can get these from Radioshack, auto parts stores, Car audio, and alarm shops have them as well. Make sure you get the harness to go with it, otherwise you'll either be soldering directly to the legs, or you'll have to go back out to get the harness later.


    If you don't already have it, now would be a great time to pick up a wire terminal set with a crimper.

    Probably the only specialty tool you'll need is for the sensor itself. However you could use an adjustable wrench, 7/8" wrench. But the proper socket is fairly cheap, and worth having.
    As you can see from the image below the socket has a slice up the slide, which allows for the wire to sit outside the socket, and not interfere with putting the sensor in.

    Last edited: Oct 5, 2009
  2. TrailLeadr

    TrailLeadr Epic Member 5+ Years 1000 Posts

    So let's get started.

    First let's get the vehicle either supported on jack stands so you can crawl under comfortably, or up on ramps, which I prefer. Chock your wheels, set your parking brake. Your safety is paramount. You can't enjoy the fruits of your labor if you don't live long enough to do the job.

    Now a visual inspection of your current exhaust pipe where the oxygen sensor is a good idea. If your pipe is rotting, and ready to fall apart, you'd be best to have it replaced, or do it yourself now while you're under there.

    Using a ratchet, and the Oxygen sensor socket remove the old sensor, and discard it. Or save it, if you like. At this point since you're under there, you can install the new one now, and leave the wires hanging for the moment.

    Once the sensor is installed you're off to the next step, providing power to the sensor.
    For my application, I'm tapping into the fuse on my fuel pump. It's easy access, it's already under the hood so no wires to run through the firewall.
    Also, all of my other connections for the relay will be made here, so minimal wire will be run.

    Next to the fuel pump fuse, you'll notice a row of terminals. Those are all positive leads. I'll be using those as well.

    This is the schematic for the project:

    The black lead on the sensor is the signal wire. This will get connected to the only wire that hooked up to your original sensor.
    The two white wires are for the heater. The heater has no polarity, so it doesn't matter which of the two white wires goes to the ground, and which goes to the relay.
    The gray wire from the sensor is the sensor ground. Therefore, it get's grounded.

    In the schematic the "hot in run" wire goes the cold fuel pump wire when the key is on and fuse is pulled. I would suggest changing to the fuse to a 25amp to be on the safe side. You'll need a multimeter to test for the cold side.

    Most of these relays have 5 poles. Make sure that the connections are made so that the switch in the relay is open when not energized (as viewed in schematic above) The relays also have a small schematic on them that will help you decipher the proper way to hook it up accordingly with the above schematic.

    In schematic, the positive line that goes to switch side of relay is going to terminal post located next to the fuel pump fuse.

    The last step is optional, but provides the best results. This would be to have your chip reprogrammed to seek the O2 signal sooner. Which will put it into a closed loop status earlier, and lower the idle. Otherwise it will still idle higher, since the ECU is programmed for a timed warm up idle.
    Last edited: Oct 5, 2009
  3. Paul M

    Paul M Rockstar

    Sorry, I do not understand the need for heating the O2 sensor. If you start the vehicle up, then you should drive it. It will warm up quicker under load and use less gas. I am in AZ now but lived in CT for 31 years. I was never one to have to warm up the car. Now in AZ, I do not wait for my car to cool down after work when it is 140 deg + inside. I get in and drive it. C'mon, you want to save fuel, put your arse in there and drive. Heating the O2 sensor is misleading and I suspect it reduces your mileage.
  4. Cableguy

    Cableguy Epic Member 5+ Years ROTM Winner 1000 Posts

    Paul are you kidding me? Come cold weather this is an awesome idea. I think you've been away from CT to long. My work van goans and clunks and whines if I try to do that at 40F the other day. I think this conversions is pure genius. My TB acts the same if I don't wait for idle to come down, the tranny shifts slow, the revs come way up. I've seen the engine tranny pre-mature failures up close and personal from the jack rabbit start and go stuff. On a hot summer day sure I can take off sooner but at I think I'll wait for it to warm up, Thanks
  5. TrailLeadr

    TrailLeadr Epic Member 5+ Years 1000 Posts

    Feedback welcome

    Paul, you're certainly welcome to your opinion, and I didn't expect everyone to fall down, and lay praise over this conversion. (just Jamie:winktongue:)
    But I have to disagree with the idea of jumping in and drive. My trans was just rebuilt, and I have no intention of dropping it into gear while it's idling at 1500rpm. It puts undo stress on the clutches, and steels, and over time will wear them out prematurely.

    I just wanted to share this conversion with our club. It's up to each member to decide if the conversion is right for them, and obviously it's not for you.
    Last edited: Oct 5, 2009
  6. Crawdaddy

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

    heh, for rushing you, I'm sure being really pokey in getting this one done. Bravo in this awesome mod. I don't know if I really need this or not, but when you mentioned it might improve MPG, I'm all ears :)

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