O2 Sensors problem

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Joe Boston
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Location: Winchester, MA

O2 Sensors problem

Post by Joe Boston » Sun Jul 30, 2017 8:15 pm

So after a few month of having the O2 sensors light come i decided to replace it.
But after replacing the oxygen sensor i still have the light come on when it warms up, then it will shut off, but it stay mostly on, not sure what else could affect the O2 sensor.
has this happen to any one?
1980 E12 Ascatgrau 5 speed
2001 E38 740 Black
2012 F12 650 IC black

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Robert Bondi
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Post by Robert Bondi » Mon Jul 31, 2017 3:21 am

I retrofitted my 77 to use the late FI with the O2 sensor, but I'm pretty
sure there is a reset switch that might need to be reset after changing the sensor. There is a reset switch on the inside of left frame rail on the 77 just under the driver - that box has a different purpose on the 77. Worth checking at least...
Robert
77 530i
77 Euro 528

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Joe Boston
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Location: Winchester, MA

Post by Joe Boston » Mon Jul 31, 2017 9:15 am

Ok, I check the speedometer box under the front rail, I pushed the button to reset it, but to no change. I did it with the car running, and engine off with key on, and with the key off.
do you know if the single wire to the o2 sensor should have 12v. going to it perhaps i can test it?
1980 E12 Ascatgrau 5 speed
2001 E38 740 Black
2012 F12 650 IC black

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Mike W.
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Post by Mike W. » Mon Jul 31, 2017 11:05 am

Single wire should not have 12V running to it. Reset the speedo cable box again. I think there's two buttons on it. Push one, then push the other, then repeat. It always seems to take two pushes of the button to reset it. Engine does not have to be running, it's a mechanical switch triggered by mileage. Make sure you have a small screwdriver or something, the switches are flush and need to be pushed into the recess some.

The warning light is triggered off that box, it has nothing to do with how the O2 sensor is functioning.
Mike W.



1980 528i, 3.5 euro, 5 speed conversion
1981 528i, 3.6, Recaros and more. Project
1998 328is, quick and efficient, but not satisfying
2000 528iit, Vacation mobile/wife's grocery getter

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Joe Boston
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Location: Winchester, MA

Post by Joe Boston » Fri Aug 04, 2017 10:01 am

well i removed both caps on the speedo box and the upper one has a small button to press in, with a small Allen wrench or screw drive. But when i push it in nothing clicks or resets, it's pretty much a weak spring.
Then i went to the second cap and there is a blank hole nothing to push in.

So i think i need a new speedo box someone must have tampered with it.
does sound accurate?
1980 E12 Ascatgrau 5 speed
2001 E38 740 Black
2012 F12 650 IC black

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Lock
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Post by Lock » Sun Aug 06, 2017 2:01 pm

Try unplugging the electrical cable from the speedo box, see if the o2 light goes out. If yes, then the speedo box may be damaged.
1979 528i 5-speed conversion G260/6, Motronic 1.3 179
1980 Honda CX-500

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RonDwyer
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Post by RonDwyer » Sun Aug 13, 2017 11:49 am

Or take the bulb out of the indicator. I turned mine into a 'check engine' light when I did my conversion. Ca says it has to be there if the later model engine came with it. Glad I didnt put in an OBD-II conversion.
Ron Dwyer
SF Bay Area

97 528i
03 530i
59 220S

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