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I've always wanted to know if the 02 light that comes on at 90k miles would go off at 180k miles, if it were left alone. Yesterday I proved that it does! on at 179,999, off at 180,001. So, unless the light bothers you, just wait another 90k miles and it will turn off on its own.

-Tad
 

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what was the reason why it was on in the first place? Also, what is the "normal" procedure to reset the light?

Con
 

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The light turns on every 90k miles to remind you to replace the O2 sensor(s). It may or may not even turn on in the OBDII Isuzus - depending on if the computer reminds you to do it or not.

The normal procedure to reset it is to remove the console and either flip a switch, or move a screw from one hole to another, depending on which console you have.

-Tad
 

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Con- Some pre 1996 vehicles did this to prompt you to change your O2 sensor(s) at 90Kmi intervals. Dealers probably made alot of money at this!! :evil: All you had to do was move a screw/jumper on the back of the instrument cluster to reset the O2 sensor dash light (every 90Kmi). O2 sensors of today can go way past 100Kmi + our nice & complicated OBDII system will clue us in if it detects any issues with any one of the four O2 sensors on 1996+ zu's :roll:

Joel

(Ooops! Sorry TAD.. you beat me too it!)
 

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A friend has a 1991 trooper - and his O2 light was on -- to reset it we removed the 4 screws on the black plastic trim, then removed the spedo - there were two screws. Then, we removed the spedo cable - just reached under the dash and squeezed the release on the cable, then removed the spedo.
We were expecting to find a screw to move from hole A to hole B -- but there was a switch instead! We moved the switch from position 1 to 2, and now the O2 light is off! Thanks.
 

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well i'm just shy of 210k now...... only 60k more to go :roll: i really have no desire to switch off the light it doesn't really bother me it was engineered to get the dealer some extra coin... kind of like this deal on the P'up forum that i saw where a guy went to his local dealership and they told him 110 for the rear window gasket on his P'up..... Jerry told him 48 shipped to his front door..... :roll: sorry i digress
 

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O2 sensors of today can go way past 100Kmi + our nice & complicated OBDII system will clue us in if it detects any issues with any one of the four O2 sensors on 1996+ zu's
OBDII may tell you about a complete failure, however sensors can get weak but not enough to trip the computer. A weak sensor will cause the engine to run rich and your mpg will drop. I always replace them if I see the mpg going down over time. I replaced the ones in my rodeo around 100k miles and picked up 1 or 2 mpg.

I liked where the switch was on my mighty max. Just pop a cover off the dash that looks like its covering a hole for an accessory switch and it was right there. Can do it while driving.

Dont think my '99 has an o2 light. Nothing happened when I hit 90k miles.
 

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Tad said:
I've always wanted to know if the 02 light that comes on at 90k miles would go off at 180k miles, if it were left alone. Yesterday I proved that it does! on at 179,999, off at 180,001. So, unless the light bothers you, just wait another 90k miles and it will turn off on its own.

-Tad
if you ever took apart an instrument cluster (DONT ASK.......) there is a separate odometer counter above the actual odo. At 90,000 miles the dial (number wheel) at the end has a step in it (see pic, its smaller), this actuates a micro switch in the back (see pic) and throws the light on....then after 90k more it shuts it off. Now replacing the screw from one point to another reverses the switchs polarity and shuts the light back off until 180k when the switch activates the O2 light again. The pisser part is, its mechanical, so if you lived with it, like Tad, from 90,000.1 to 179,999.0 and you reverse the screws at 179,999, it will go back on at 180,000.... it doesnt know where the screws are and that you just changed them..... :)


 

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I picked up a speedo at the junk yard in order to replace the one in my truck that only had MPH on it. I dove into the speedo in order to recalibrate the odometer reading to match my truck and the one I got from the yard had the switch on it. However the 2.8L trucks like mine do not use it.
 

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JTK said:
Con- Some pre 1996 vehicles did this to prompt you to change your O2 sensor(s) at 90Kmi intervals. Dealers probably made alot of money at this!! :evil: All you had to do was move a screw/jumper on the back of the instrument cluster to reset the O2 sensor dash light (every 90Kmi). O2 sensors of today can go way past 100Kmi + our nice & complicated OBDII system will clue us in if it detects any issues with any one of the four O2 sensors on 1996+ zu's :roll:

Joel

(Ooops! Sorry TAD.. you beat me too it!)
Not necessarily. As Dave mentioned, the sensors will get weak and it won't know the difference. It'll know if the circuit is voltage is too high or low, but not if the readings are wrong. If the silicates in coolant coat the sensor (ala blown head gasket) the computer won't throw an error--it won't notice the slow responding inaccurate data. There's a reason they are replaced every so often--it's not just to make dealers money :roll:
 
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