Re: Dangling Wires

[Steve Manning <stephenm@ix.netcom.com>]

Much snippage, but I wrote:

>>By the way, did you pull the codes?  You should have had an error code set
>>when the ECU determined that it should be getting a signal from the O2
>>sensor and wasn't getting one............SLM

And Mike Bywater responded to that particular point:

>Well, I'd like to add a bit to this...
>
>The O2 sensor is nothing more than a voltage generator. The ECM does _not_
>have the ability to verify the sensor's temperature or accuracy. Closed loop
>operation is determined by coolant temp. Once coolant temperature rises
beyond
>a predetermined point (usually about 170 degrees f), the ECM then uses the
>O2's output voltage in it's determination of proper fuel mixture.
>
>If the sensor is disconnected (or dead for that matter), the ECM will see
zero
>volts from the O2 circuit. This is registered as a lean condition, and the
ECM
>will respond by increasing fuel. This is the reason you should verify
catalyst
>function, as an overly rich condition can damage it.

Actually, the ECM is smart enough to determine that it is not getting a
signal from the O2 sensor when it should (I'm not sure how, however,
although I could guess).  Test this out by disconnecting your sensor.
After driving around for a while and getting things all warmed up, and the
ECU will set a '2342' error code, which is defined as 'Oxygen sensor
disconnected or defective', and will then go to a predetermined default
map.  You'll sometimes also get a '2341' for 'CO content not within
specified range' or 'faulty ground connection to oxygen sensor'.  These are
for the 5-cylinder after 1990, but others years/models are similar.  This
has happened to me, BTW.  So pull those codes, everyone.........SLM

Steve Manning:  stephenm@ix.netcom.com
...Physical home: Metro D.C. area, USA
.....Virtual home:  http://www.stationwagon.com