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oxygen sensor

Discussion in 'EEK! - Every Extended-K Car' started by willrappold, Apr 25, 2018.

  1. willrappold

    willrappold Active Member

    Jan 23, 2013
    I have code 21 on my 85 reliant se 2.2L TBI. I had a replacement senor put on a couple of years ago. I just not sure if I need a heated sensor or non heated. I have to crawl under and look if I have a 3 wire connection or just 1. Any suggestions on which to buy? Thanks.
  2. Doug D

    Doug D Virginia Gentleman

    Aug 10, 2000
    As far as brand it's recommended to go with OEM, but I have had good service from Eglin (NAPA) O2 sensors.
  3. Bob Lincoln

    Bob Lincoln "CHECK FAULT CODES"
    Level 2 Supporter

    Jul 10, 2002
    You don't have to crawl underneath. The O2 sensor on 4-cyl K-cars is readily visible from the driver's side fender, looking from above. I believe it will be non-heated for that vintage. It could be either one-wire or two-wire, as initially they were grounded through the manifold, but then had a dedicated ground wire.
    Do NOT use Bosch brand. They fail early and are inaccurate. They only have 4 slits up the sides for sensing, whereas other brands have 32 holes around the tip for rapid and full response. Denso and NTK are good brands.
    Doug D likes this.
  4. Chrononaut

    Chrononaut Member

    Jun 30, 2016
    Hi, willrappold. Your 0-2 sensor is a one wire, non-heated sensor. Bob Lincoln is right. you don't have to crawl under your 'K' to replace the sensor. I replaced mine in my '87 reliant last year (time to do it again, though!). All you really need is an 0-2 sensor socket, 1/4 " drive, (about 8 bucks, but you might need it again for your car later or loan it to a socketless friend), a long 1/4" drive extension (got mine at a thrift store for .99) and a cool motor. Remove the air cleaner and heater tube and GENTLY move the wires and hoses that will be in the way. Don't worry, the sensor is visible with the air cleaner removed. Then just un plug the single sensor wire, guide the wire on the sensor through the slot in the socket as you push the socket over it, just like a spark plug. Use of the long extension comes in handy here so you won't be busting your knuckles on the underside of the intake when removing and installing your sensor. Be careful when starting to thread it in, the threads are easy to damage if cross threaded, and make sure there's some anti seize compound on the threads. Just like installing new plugs in aluminum heads, you want to make sure the engine's cold or you'll gall the new sensor! I bought mine off Rock for pocket lint, but I got what I paid for - crap! My next one's gonna be Denso or NTK! Good luck with your car! Oh, yeah, most importantly! Disconnect the battery before R&R'ing the sensor so the computer will learn the new one quickly (at least that's what I was taught!) Mopar to ya!
  5. AllanC

    AllanC Well-Known Member

    Jan 6, 2003
    Before you fire the "parts cannon" and blindly replace the oxygen sensor, do some checks. Code 21 for this vintage automobile indicates no sensor signal for 5 seconds or more. You could have an issue with an open or short in the oxygen sensor signal wire. Trace the single wire from the sensor back through the fire wall to the logic module. Since it is a single wire sensor, it relies on a good ground through the body of the sensor to ground to the exhaust manifold. Maybe the last time it was replaced excessive anti-seize thread compound (necessary to prevent it from welding itself into the manifold) was used and the return circuit ground is electrically insulated.

    This video shows how to test an oxygen sensor without sophisticated diagnostic equipment. Note that the video starts at time interval 1:33. There is IMPORTANT information relayed about testing so start the video at the beginning segment.

    how to test a one wire oxygen sensor - Google Search (at )

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