Low O2 sensor readings

[Kurt Bilinski]

At 10:18 PM 5/22/97 -0400, you wrote:
>
>I hope yall can help with this one.  Doesn't everyone love a good mystery!
>
>I have been getting a lot of 13 codes on my Monte (O2 sensor fault).  I
>connect a DVM to it and it seems pretty normal, around .4V at cruise, .5 to
>.6 V under acceleration, .3x V or so at idle.  However, at idle in gear,
>when watching the O2 voltage on the DVM, using turn signals make it flip
>flop around by about .15V or so.  Turn on lights, it drops near .30 or .2x,
>turn on AC and blower motor and the O2 voltage drops to .1x volts!
>


Dead giveaway of a ground loop...

Make sure all ground connections are clean and tight.  Has this always been
a problem?  If not, then some ground wire is loose or fallen off.

Kurt