I am not sure if it would cause any damage to the ECU, but I would be wary
of putting 12V on the oxygen sensor input to the ECU, as it is only
expecting a low amperage signal between 0 and 1V.

If 12V indeed has no bad effect on the ECU, and convinces the ECU that it is
a fully rich condition, then I would agree that this would certainly would
cause the engine to go lean.

However, if you are just checking to make sure that there is continuity on
the wires, grounding the input, causing the engine to run rich, would
probably be sufficient.

Craig in Cupertino

> -----Original Message-----
> From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf
> Of Dennis Haynes
> Sent: Friday, October 31, 2014 2:03 PM
> To: vanagon@GERRY.VANAGON.COM
> Subject: Re: Single wire Oxygen sensor: Substitution report..
>
> The sensor does need a return path and it is done through the exhaust
> and engine. There has to be a complete circuit. The ECU sensor input can
> also be tested with a battery. Ground the input and the engine should go
> rich, connect the battery positive terminal to the lead and ground the
> negative and the engine should go lean.
>
> Dennis
>