Keep in mind that in most vehicles, the sensor ground or returns are
not chassis/battery grounds, they are reference grounds provided by
the ECU to control/prevent voltage fluctuations and offsets... so you
might not be doing the right thing by simply grounding them. Re-check
the stock diagrams for this.. from the description (esp. with the
mention of the ECU/engine management in the one description) maybe
this is your issue.

Jim Akiba

On Sun, Jun 22, 2008 at 12:18 PM, neil N <musomuso@gmail.com> wrote:
> Hi all.
>
> My Jetta ABA 2.0 OBD1 conversion *was* running crappy. TPS and ECT
> weren't grounded. (D-oh!) Grounded them, engine runs better, but I
> still get error codes for TPS, ECT, and CMP.
>
> I conveniently wired the TPS, ECT, and CMP to share the same physical
> ground location.
>
> But..... Bentley shows them using grounds at (presumably) different locals.
>
> i.e. "Sensor ground", "MFI Motronic Multiport Fuel Injection"
>
> In archives, I read of Vanagon O2 sensor issues related to shield on
> coax and ground wire sharing the same physical ground location. This
> tipped me off.
>
> So.....
>
> If TPS, CMP, and ECT share the same ground connection (location),
> would this cause these error codes? Would sharing the same physical
> ground connection hinder performance and/or damage these parts?
>
> If I can leave it as is, I will. I don't understand what/where Bentley
> is referring to when using the various terms for different ground
> locations.
>
> "Fussy" questions, but it would be nice to get this "right".
>
> FWIW,  these are the only 3 error codes (so far --- ;^)
>
> Many thanks,
>
> Neil.
>
> --
> Neil Nicholson '81 JettaWesty "Jaco
> http://groups.google.com/group/vanagons-with-vw-inline-4-cylinder-gas-engines
> http://web.mac.com/tubaneil
> http://tubaneil.googlepages.com/
>