GMECM Digest V2 #964

[bcroe at juno.com]

The impedance of the cable is not too important
in this situation: low frequencys, high impedance
circuits, and of course no terminations.  The ideal 
situation is both ends of the cable are tied first to
the same ground point.  Since the OX sensor is
grounded to the engine, the ECM should be 
grounded there too.  That means NOT grounded 
to the body of the car.  If your ECM is grounded to
the engine, you can tie the shield to the ECM gnd
and the engine gnd, since no outside currents 
will be flowing through that path.  If the ECM has
another ground, probably the best setup would
be to ground the OX sensor at the engine end 
only to at least shield that noisy environment. 

A better solution is an OX sensor that is not 
grounded to the engine.  Most other sensors 
that used to be grounded to the case, have
migrated to this arrangement in recent designs.

Bruce Roe

On Sat, 26 May 2001 22:51:06 -0400 "Keith D. Miller"
<kdmiller at westnet.com> writes:
> > -----Original Message-----
> > From: owner-gmecm at diy-efi.org 
> > [mailto:owner-gmecm at diy-efi.org]On Behalf
> > Of Don Burns
> > Sent: Saturday, May 26, 2001 9:59 PM
> > To: gmecm at diy-efi.org
> > Subject: Re: GMECM Digest V2 #964

> Lookup ancient RF grounding practices, this is oldhat. If
> you ground one end, or tie both ends to the same ground
> point, the shield will become a true shield. If you tie
> both ends to different ground points, the ground
> differential between the two points will cause current flow
> in the shield and unpredictable results.
> 
> Keith
> --
> 
> > Len, did you ground the shield at the ECM end, and if yes,
> > did you connect the shield to the ECM housing or to the O2
> > input ground terminal? My application is with a 730 ECM.
> > As I recall, the schematic in the archives shows a simple
> > RC network at the O2 input of the ECM. Do you have any
> > idea what the R and C values are?
> > 
> > Don
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