Re: Ground Loops (non aviation)

[Jennifer Green & Scott Peitzsch <jlg-sep@mediaone.net>]

>> On grounding:
>> GM seems to ground all the ecm stuff thru one point on the engine.
>> Somestimes on the heads, sometimes on the intake.  I would
>> **ASSUME**, this is to prevent ground loops?.  Is the reason cause
>> of where the alternator is grounded there, or the mass of the block
>> to act a sort of a capacitor, or what?.  Would there be a big
>> difference in grounding things at the firewall, and relying on the
>> original ground strap, and battery cable to be the grounds?.....
>
>One would think that the O2 sensor ground would be nearest the
>engine block ground....  Any large offset to the firewall would really
>mess that up.

Single point, or "star" grounding is a simple way to avoid ground loops,
but as Scot alluded to above there is probably another reason for it.
Many critical sensors rely on the engine as their ground (like the ECT,
knock sensors, oil pressure, etc...), so minimizing the number of
connections that can deteriorate over time between the sensor and the
PCM just makes good sense.  I'd guess this is the primary reason for it.

-Scott
----------------------------------------------------------------------------
To unsubscribe from gmecm, send "unsubscribe gmecm" (without the quotes)
in the body of a message (not the subject) to majordomo@lists.diy-efi.org