From digest.v7.n371 Fri Oct 3 09:24:15 1997
From: Jim Cash <j.cash_at_sympatico.ca>
Date: Fri, 03 Oct 1997 09:11:12 -0400
Subject: Re: Oxygen sensor Warning light - 528e
This will not be a complete answer about your O2 Warning Lamp since I am
working from memory only - But
The warning lamp is not "connected" to the sensor circuit. It was
designed to provide a warning when the car went over its "initial"
milage period (I can not remember what the milage was but it may have
The intent was so that the car would pass environmental laws. It was
recognised that the O2 sensor had a life span and should be replaced. To
satisfy the environmental legislation they put in a device that set off
the O2 warning lamp, but only once (at whatever that milage point was)
This was accomplished by a small replaceable fuse in the back of the
instrument cluster. When the odometer reached the "chosen" milage point
it caused a short across this fuse that caused it to blow - the
electrical result was that the O2 warning lamp lit.
At that time the dealer normally replaced the sensor and removed the
fuse unit - this way the lamp would never light again.
( I may be wrong on some of this detail - it has been 12 years since it
happend and I no longer have the drawing showing the circuit )
My dealer simply tested the sensor and did not change it, saying that
they last much longer.
In fact I never did change mine. I had the car 14 years and 280,000kms.
Since it was easy to pull the sensor out all I ever did was use a wire
brush and a fine toothed "pick" to keep the slots in the sensor open
(they originally used to clog with exhause deposits but after Shell
modified their gas in about 1988 (?) I never seemed to have many more
Throughout this time I had the sensor and CO levels tested occasionally
- - they were always within original limits.
If you do go into that back of the instrument cluter to remove the fuse,
or replace it, it is located on the upper right (looking at the back of
the cluster) behind the speedometer. It is a 0.1 amp fuse. The old
diagram I have of the cluster says "unsnap cover, pull fuse to remove."
I am puzzled as to why your lamp came on at 160,000 miles. As I said it
should have been at a much lower milage. The only thing I can think of
was that someone reset the system (new fuse) and it has triggered again.
That is what made me think the original milage should be 60,000 - maybe
the circuit is triggering on the 6 in the 5th digit wheel. I think I
remember looking at this once and realising it was a tiny sensor on the
odometer wheels - can't remember the physical details.
Hope that helps.
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