With your ohm meter, check for continuity between each signal or power
supply wire and ground from the main CU plug. You're looking for a route to
ground that shouldn't exist, due to melted wires inside the harness or an
interior insulation failure in a component.

In the case where a component has a ground directly to the chassis (like the
fuel pump), remove the ground connection before testing so you know that if
you get continuity to ground there is either a short internally or a wiring
fault. If you do get continuity to ground, pull the plug and test again. Now
if you get continuity the problem is in the wiring, if not, it was in the
component.

In the case of a component that has a ground return back to the CU (like a
temp sensor) just check with the thing connected. If you get a continuity to
ground, disconnect the plug from the component. Then if there's still
continuity to ground there's a wiring fault. (In that case, start
disconnecting the other connections until continuity disappears.) If no
continuity to ground with the component connected, the component's bad or
the ground return is shorted to another wire. Pull the connector from the
suspect component and check the ground return wire for continuity to ground.
Since the ground return is supposed to go back through the computer (but it
can't since the plug is disconnected from the CU and is in your hand), if
you get continuity to ground through the disconnected ground return wire
it's obviously shorted to some other wire and going to ground that way.

This makes sense to me - I hope it comes across clearly. Diagrams are so
much better!

This all depends on your having adequate wiring information - the Bentley
book is what we use.

Good Luck!

Coby

Valley Wagonworks
"Intimately acquainted with VW Vans since 1959"

Volkswagen Bus, Vanagon, Westfalia and Eurovan
Repair and Service Specialists

1535 Sir Francis Drake Blvd., San Anselmo, CA 94933
Voice:(415) 457-5628
Fax: (415) 457-0967
http://wagonworks.com
mailto:contact@wagonworks.com

> -----Original Message-----
> From: Vanagon Mailing List [mailto:vanagon@GERRY.VANAGON.COM]On Behalf
> Of Caston/Payne
> Sent: Saturday, September 04, 1999 8:54 AM
> To: vanagon@GERRY.VANAGON.COM
> Subject: Re: Digijet ecu failures, "Bosch - Bosh?"
>
>
> <Add to this a test for short-to-ground through
> every wire not intended to be a ground.>
>
> How does one go about that?
> Later,
>
> Dave & Sherrie
> Williamsburg, VA
>            zzzzzzzzzz__
>          |E[__] [__]|[_]\\
>          | _DC&SP | _ ||
> * * * =-( )---------( )--=
>