Date: Thu, 21 Mar 2002 11:42:47 -0500
Reply-To: Laurence Smith <lsmith@COGECO.CA>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Laurence Smith <lsmith@COGECO.CA>
Subject: Re: Cough, Choke, Splutter!
In-Reply-To: <F214N2tEwLqJrfP6nmG000190a6@hotmail.com>
Content-Type: text/plain; charset="iso-8859-1"
Mike,
Your O2 wiring sounds right. Please note: The white wire that attaches
to the ECU cannot be seen. It is inside the harness.
The spade connector (where the green connects to the black) is the
core (+'ve portion) of the O2 signal. For the ECU to use this O2
signal properly there has to be sheilding and the green coax wire has
this sheild starting about 1" after the spade connector. If you look
closely at the green wire spade connection (about 1" inwards) you will
see the green wire goes from a small diameter to a thicker diameter
with a slight ridge. This ridge is the start of the outer ground
sheath.
This sheilded green wire goes into the harness and near the ECU it
branches off. The outside ground sheath branches into a white wire
and this white connects to Terminal 19.
The white coax wire in Bentley has nothing to do with the spade
connector or the O2 white wires. It is just an unfortunate
coincidence that the colors are the same which causes some confusion.
As for the theory, I think that there is an internal break in the
ground wire coming off Terminal 19. In the Vanagon archives there is
talk about replacement O2 wires due to a breakdown in the coax
sheathing. VW actually has a part number and replacement for the
entire O2 green wire and sheathing so this tells you that the problem
is known.
When I was trying to solve my problems I did almost everything to try
to do the fix. It took me 3 months to resolve it. The Terminal 19
ground was the culprit. To satisfy myself that is was fixed, I can
remove the new ground and the symptoms return 100% of the time.
Even when the O2 sensor was disconnected the problem was still there.
This told me that the internals of the coax wire were faulty. I was
getting ready to replace the whole green wire when I decided to try
just adding a new ground to Terminal 19. I think that the coax wire
degrades with time and the outer sheath either shorts to the inner
core or the ground fails. In my case the Terminal 19 ground failed.
Laurence Smith
Hamilton, ON
90 Westy (fanumbos)
> -----Original Message-----
> From: Mike Finkbiner [mailto:mike_l_f@hotmail.com]
> Sent: Thursday, March 21, 2002 11:02 AM
> To: laurence@alanasmith.com
> Subject: RE: Cough, Choke, Splutter!
>
>
> Laurence -
>
> That's quite clear. If it stops raining/snowing this
> weekend, I will tear
> into the wiring.
>
> Couple of questions -
>
> Any theory as to why it would act up with the O2 sensor
> disconnected?
>
> In Bently, it shows the shielding around the O2 sensor wire
> connected to the
> ECU at pin 19. When I look at mine, I see a spade
> connector for the signal
> wire, and a double connector for the heater wire.
> Nothing that looks like a connector for the shielding. Did
> the DPO remove
> something? This sensor is referred to as a 3-wire, but I
> sort of assumed
> that it was three plus ground.
>
> Thanks for your help!
>
> - Mike
>
> >>>>>>>>>>>>>>>>>>>>>>>>>>
> Mike,
>
> I will try to explain my fix in more detail.
>
> On the Bentley diagrams the White wire that attached to
> terminal 19 is
> internal in the harness and you can't see it. Don't confuse this
> white shunt (that you can't see) with the white wires on the O2
> sensor. This internal white wire is the ground for the
> outside sheath
> of the green coax.
>
> To do the fix I did, you need to tap into the correct
> ground wire near
> the ECU connector. Then you run this new ground back to the engine
> and attach it somewhere. I used the distributor ground tab for my
> attachment.
>
> On page Bentley 97.106 your equivalent ground wire is Brown
> and comes
> off terminal 19. Yes, the same one that the White attachs
> to. I see
> from the diagrams that you have two(2) Browns coming off the ECU.
> What a pain. No wonder they changed it from 1988 onwards. You will
> need to identify the Brown that comes off terminal 19.
>
> On my 90 Westy, my Terminal 19 ground was Brown/Black so it was easy
> to identify in the ECU connector wire cluster. I tapped my
> new ground
> wire right on to the Brown/Black wire near the connector.
> I stripped
> back about 1/2" of the insulation and twisted the new ground to the
> exposed wire. You need to be vary careful doing this. Once
> connected, I ran the wire back to the engine.
>
> Remember, the new ground wire does not have any physical
> connection to
> the existing O2 sensor or its wiring. The ground wire fix is to
> provide the correct impedence to the ECU for the signals
> travelling in
> the green O2 sensor wire. The ECU picks up on this. If
> the impedence
> it screwy because of the lack of a decent ground, then the
> O2 signals
> are messed up. Like you, I was reading 8.0-9.0 volts at times. The
> new ground fixed this.
>
> Just grounding the ECU will not provide the necessary fix. You need
> to attach to the Brown coming off Terminal 19.
>
> Good luck.
>
> Laurence Smith
> Hamilton, ON
> 90 Westy (fanumbos)
>
>
> Mike Finkbiner
> mike_l_f@hotmail.com
>
>
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