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Date:         Wed, 30 Jul 2014 13:08:17 -0700
Reply-To:     Neil N <musomuso@GMAIL.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Neil N <musomuso@GMAIL.COM>
Subject:      Re: Another question about O2 sensors..
Comments: To: Don Hanson <dhanson928@gmail.com>
In-Reply-To:  <CAHTkEuJeA0E9jgtSW4iVdEzUh=6-W3vxkXTLq8NcSWHeEUM7QA@mail.gmail.com>
Content-Type: text/plain; charset=UTF-8

> ..... the ECU most > likely has a common ground that allows signals to be sent to it without > having another ground wire going all the way back to the source...

I will speak somewhat ignorantly as I'm learning as I go but......

It varies depending on the engine management, but from what I've seen, an ECU may have several ground wires. So inside the ECU, there may be different discrete grounds for certain circuits. But I think you're on the right track. The ECU components that process the O2 voltage output need a positive and negative connection as does the O2 sensor itself. All DC circuits require a positive and negative connection to function. Exactly how various ECU ground pins connect to vehicle frame (ground locations, physical routing of ground wires in a harness, etc.) obviously depends on engine management, model year, market sold etc.

The part that gets a little confusing for me is the shielding around the O2 positive ("signal") wire. I understand it's function, but on the 2.1 WBX it connects to an ECU pin and that ECU pin connects to vehicle negative. That said, I'm sure this topic is covered in the archives. Regardless, on a Mk2 Digifant 2 diagram I looked at, this shield runs straight to ECU only. But that pin may have an internal path to vehicle frame via another pin to wiring harness.

I know it's a PITA, and I make no claim to be completely adept at reading them, ;) but for me it has paid 10 fold to learn.

On 7/30/14, Don Hanson <dhanson928@gmail.com> wrote:

> My assumption for connecting the single wire Bosch sensor like this, with > just the one signal wire attached back to the ECU is that the ECU most > likely has a common ground that allows signals to be sent to it without > having another ground wire going all the way back to the source... > > ....I just don't know and I > am unable to follow a complex wiring diagram to suss out the answer... >

-- Neil n

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