heated vs non heated O2 sensor with headers

Discussion in 'Engine Performance + Maintenance' started by kenh, Jan 12, 2021.

  1. kenh

    kenh I'm Awesome

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    1990 C1500 5.7 TBI

    I've read some are using a heated O2 sensor when running headers. Necessary or not???

    If a heated sensor is preferred which unit are you using? Where do you get power for the heater? Just find a hot, key on wire? Because I have no idea are the heated sensors 3 or 4 wires and if 4 wires where does the 4th wire go?

    I'm asking because I certain my O2 sensor is contaminated when I had a head gasket leak. Of course it leaked water into the left bank and that goes right by the sensor. If I have to replace it I might as well "upgrade". 1990 C1500 5.7 TBI

    Thanks!

    Ken
     
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  2. PlayingWithTBI

    PlayingWithTBI Desert Old Guy

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    I'm running a 3-wire one in my shorty headers. I looked it up on Amazon which shows I bought these on 8/21/18 so, I'm going on 3 years without issues. The advantage of having a heated O2 is you go into Closed Loop a lot faster and stay in CL when at idle where, a non-heated sensor and free flowing exhaust without a lot of back pressure it'll go in and out of CL. When I start my truck and let it idle for a minute before I drive off, it'll go into closed loop shortly after I get out of the driveway.

    The 3-wire sensor still uses the threads for the ground on the sensor and the other 2 are for the heater. The 4th wire is to ensure a good ground to the sensor. Yes, you just find a key-on source and hook up the heater to it. If I had to do it over, I'd probably go to the 4-wire setup but, as I said 2-1/2 years and no issues.

    Here's the sensor I got.
    https://www.amazon.com/ACDelco-AFS7...dchild=1&keywords=AFS74&qid=1610555680&sr=8-1

    Here's the adapter. It makes it easy to upgrade, red to hot, black to ground, and the 1-wire connector goes where the old sensor plugged in.
    https://www.amazon.com/Michigan-Mot...ich+motor+sports+22300&qid=1610555784&sr=8-13
     
  3. kenh

    kenh I'm Awesome

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    Perfect!! Thank you!
     
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  4. Pinger

    Pinger I'm Awesome

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    The surprise for me here is 'hot at all times'. For some reason I thought they switched off once the sensor was up to operating temp. Would that be the case when they are under PCM control (and operating temp can be ascertained by seeing fluctuating signal output)?
    Even if so, 3 years trouble free says hot at all times isn't hurting them.
     
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  5. PlayingWithTBI

    PlayingWithTBI Desert Old Guy

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    I couldn't tell you if the PCM controls the heating of them or not. I wouldn't think it would just because of current draw without a relay? Besides, that OBDII stuff is way too new for me:Big Laugh:
     
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  6. Frank Enstein

    Frank Enstein I'm Awesome

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    They stay hot all the time the engine is running. Don't hook it to accessory hot. 3 wire is usually fine. I like to hose clamp a ground wire on the hex of the sensor and run it to the engine block. A bad ground makes the computer think the engine is lean.
     
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  7. Pinger

    Pinger I'm Awesome

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    Looking at Haynes (1996 onwards), the heating elements are all fed from a feed (marked 'ign') from the 'vehicle control module' (which appears to be the PCM) and same feed goes to a whole bunch of stuff the engine needs to keep running - so hot at all times (when running) it is.
     
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  8. BOOT

    BOOT Newbie

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    There is an ideal distance from the head that the nonheated sensor is designed for, I forget what is it BUT if you look at an oem short header manifold type like a C4 corvette. (Some C4 owners upgrade to 3 wire still)

    Still some I've read use a toggle with their 3 wire to preheat it like a glowplug, sucks if you forget tho!
     
  9. Erik the Awful

    Erik the Awful I'm Awesome

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  10. kenh

    kenh I'm Awesome

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    So basically any wire that is hot with the key in the run position would work just fine if the above mentioned wire could not be found.

    Ken
     

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