Low O2 sensor readings

[Chief]

At 07:20 AM 5/23/97 -0700, you wrote:
>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

I didn't really notice the voltage drop until I put a DVM on the O2 sensor.
It has been a problem for a while.

Where are the basic grounds I should check for?  I assume battery to body
panel, computer grounds, battery to engine.  My ground cable goes to the
alternator bracket on the Monte.  Should it ground to the block?

I had to change a head on my car a while ago and maybe I didn't ground
everything back correctly.  :-(.

Ed Hilker aka "Chief"
84'SS - 700R4