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vwhammer
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Joined: May 20, 2006
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Location: Boulder CO.
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 Posted: Tue Apr 21, 2020 10:09 am Post subject: Another Simple Question - Name That ABA Plug |
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Building my ABA Vanagon with an engine and harness from a 98 jetta.
I was looking at my wiring harness to make sure I knew where all the plugs went.
I got all of them sorted except one.
This is the plug in question.
I have looked through all the old components I got from the donor car and everything else is plugged into something but I just can't sort where this one goes.
Unfortunately I do not have any kind of manual for the donor car and the nets are useless for tracking down wiring diagrams.
Anyone have any ideas? |
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vwhammer
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Joined: May 20, 2006
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Location: Boulder CO.
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dkoesyncro
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Joined: December 10, 2006
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| Posted: Tue Apr 21, 2020 12:03 pm Post subject: Re: Another Simple Question - Name That ABA Plug |
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| Yup that's for the oxsensor, you should have a brown one for the post cat side as well. |
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Vanagon Nut
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Joined: February 08, 2008
Posts: 10379
Location: Sunshine Coast B.C.
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| Posted: Tue Apr 21, 2020 12:29 pm Post subject: Re: Another Simple Question - Name That ABA Plug |
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I've asked SO many questions on this forum so far be it for me to suggest stuff like this but... 
Can part numbers on connectors be of any use here? That said, I know VW used the same connectors on a variety of parts.
You may find a Bentley manual helpful especially after you get the swap running. I found the descriptions in my A3 Bentley for each of the sensors et al, quite helpful for trouble shooting.
You're going to run OBD2 Motronic? Do you think it would run ok with just a pre cat O2 sensor?
Neil.
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1981 Westy DIY 15º ABA
1988 West DIY 50º ABA
VE7TBN |
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vwhammer
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Location: Boulder CO.
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Vanagon Nut
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Joined: February 08, 2008
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Location: Sunshine Coast B.C.
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| Posted: Tue Apr 21, 2020 12:34 pm Post subject: Re: Another Simple Question - Name That ABA Plug |
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hmmm..... Well, AFAIK, OBD2 uses a pre and post cat sensor as dkoesyncro eludes to.
Donor is a '98 so it for sure will be OBD2.
This pin out chart might help you trace wires?
http://www.a2resource.com/electrical/management/motronicvr6aba.html
_________________
1981 Westy DIY 15º ABA
1988 West DIY 50º ABA
VE7TBN |
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vwhammer
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Joined: May 20, 2006
Posts: 998
Location: Boulder CO.
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| Posted: Tue Apr 21, 2020 12:48 pm Post subject: Re: Another Simple Question - Name That ABA Plug |
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Yeah it seems I need to take a closer look at my harness with that pinout thing in front of me
I remember that there were a couple other wires tied up with the wire going to that first plug.
Perhaps the plug was missing and those extra wires go to the second O2.
Might have helped if I was the one that actually removed the engine and harness from the car.
No matter.
I will sort it out.
I guess I am glad I posted on here or I would have totally overlooked the 2nd O2 sensor.
I am sure I would have figured it out eventually but this is a good head start.
Thanks for the link.
_________________
Pretty normal daily driver build
https://www.thesamba.com/vw/forum/viewtopic.php?t=708418&highlight=
4x4 build
https://www.expeditionportal.com/forum/threads/volkswagen-vanagon-4x4-conversion.162055/ |
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Vanagon Nut
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Joined: February 08, 2008
Posts: 10379
Location: Sunshine Coast B.C.
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| Posted: Tue Apr 21, 2020 1:01 pm Post subject: Re: Another Simple Question - Name That ABA Plug |
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You're totally welcome.
On my first ABA swap, I swear I mistakenly interchanged two sensor connectors on first start. It eventually started but ran like crap! LOL.
I have no idea where your wiring harness skills are at but mine were nearly non existent at that time. I made mistakes, had to make a few repairs - changes even after the engine ran ok. (below: van coughs up its' harness, again). I had lots to learn, still do!
I'd guess that checking the 1.8T swaps might yield info on whether or not the post cat O2 sensor could be deleted but then the cost-time savings in doing so may be negligible.
Neil.
[
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1981 Westy DIY 15º ABA
1988 West DIY 50º ABA
VE7TBN |
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vwhammer
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Vanagon Nut
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| Posted: Tue Apr 21, 2020 1:44 pm Post subject: Re: Another Simple Question - Name That ABA Plug |
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Looking in one of my Bentleys, for the 1.8T and 2.8 VR, each has this note re: post cat O2:
"Monitors catalytic converter efficiency"
So not to say this applies to your harness but as a WAG, maybe a lack of post cat O2 input to ECU would not adversely affect the engine management (engine) performance? i.e. when it "sniffs" a large enough imbalance, it might "simply" serve to turn on engine light in an effort to alert owner 'time to replace cat'. ? Anyhow.......
Neil.
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1981 Westy DIY 15º ABA
1988 West DIY 50º ABA
VE7TBN |
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vwhammer
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Joined: May 20, 2006
Posts: 998
Location: Boulder CO.
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| Posted: Tue Apr 21, 2020 6:11 pm Post subject: Re: Another Simple Question - Name That ABA Plug |
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I looked over my whole harness tonight and I did not come across any extra plug or wires that might go to a second O2 sensor.
Everything on the harness is either labeled or goes to the first O2 sensor plug I showed, the knock sensor or the crank position sensor.
Perhaps since this is the earliest version of OBD2 that was then carried over to the MK4 it does not have the second O2 sensor?
The plan this week is to get the engine and trans in the van so I can start connecting everything.
Eventually I will get to the bottom of this but for now I am not going to stress over it too much.
With all that said I am still definitely interested in any definitive info that anyone has so feel free to post up.
_________________
Pretty normal daily driver build
https://www.thesamba.com/vw/forum/viewtopic.php?t=708418&highlight=
4x4 build
https://www.expeditionportal.com/forum/threads/volkswagen-vanagon-4x4-conversion.162055/ |
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Butcher
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Posts: 1285
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| Posted: Wed Apr 22, 2020 7:32 am Post subject: Re: Another Simple Question - Name That ABA Plug |
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| ALL OBD2 systems must monitor the catalyst. Therefore it if does not have a rear O2 sensor, it's not OBD2. |
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Vanagon Nut
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Location: Sunshine Coast B.C.
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| Posted: Wed Apr 22, 2020 10:41 am Post subject: Re: Another Simple Question - Name That ABA Plug |
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| vwhammer wrote: |
I looked over my whole harness tonight and I did not come across any extra plug or wires that might go to a second O2 sensor.
Everything on the harness is either labeled or goes to the first O2 sensor plug I showed, the knock sensor or the crank position sensor.
Perhaps since this is the earliest version of OBD2 that was then carried over to the MK4 it does not have the second O2 sensor |
OBD2 became the standard in 1996. I really really doubt someone would've swapped in OBD1 engine management to your 1998 donor but......
if the donor car had a blue EVAP purge valve, the harness and ECU are most likely OBD1.
Both OBD1/2 ABA Motronic ECU have 68 pins but that A2 resource page shows each having a different pin out.
Transition dates to OBD2 may depend on market car was sold in? Up here in Canada, 2 ABA ECU's I got from cars at a wrecking yard had 1996 1997 manufacture dates but the cars had blue EVAP valves, searching the Bosch ECU part numbers showed each as Motronic 2.9 (OBD1), each ECU works fine with my OBD1 wire harness.
Images of those ECU part numbers and internal comparison of my OBD1 1993 and the 1996 or 1997 ECU's in question:
https://photos.app.goo.gl/FL9h2w6GMU4N9X7u8
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1981 Westy DIY 15º ABA
1988 West DIY 50º ABA
VE7TBN |
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vwhammer
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Joined: May 20, 2006
Posts: 998
Location: Boulder CO.
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| Posted: Wed Apr 22, 2020 7:47 pm Post subject: Re: Another Simple Question - Name That ABA Plug |
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The mystery deepens
So this engine is definitely an OBD2 engine and ECU.
It was built after 1996, had single valve springs and Techtonics sent me an OBD2 chip for my ECU based on the ECU code that I gave them.
There is definitely no extra O2 sensor plug on this harness.
However, after digging around in some of the boxes of parts that I got with the engine I came across this.
I believe this is what is left of the O2 sensor that would have plugged into the 2nd O2 sensor plug.
With the pinout list and my harness in hand I set out to get to the bottom of this.
For those that care and want to follow along I suggest you open the pinout link and have it handy so you can see what I am talking about.
So, it appears that the O2 plug that is still in my harness is for O2 sensor number one according to the pinout list that was linked up above.
I have the brown wire (actually mine is brown and white) coming from the sensor plug that runs to pin 12 on the main ECU plug.
I have the white wire that runs to pin 20 and the yellow that runs to pin 42 all as the pinout list says.
There is also an extra red and white wire on the sensor plug that runs to a relay that was supplied in the harness.
Well I don't know that it is "extra" but its just not noted in the pinout list because it does not go to the ECU plug.
Now if I move on to O2 sensor #2 it seems that all the wires have been removed from the harness.
If you look at the back of the ECU plug you can see that the holes that were not used from the factory have some kind of white plug in them.
If I trace the wires that would have gone from the ecu plug to the #2 O2 sensor it seems that they were all removed.
There is no red and white wire at pin 13 and there is no white plug there either.
The brown wire at 66 and the white or black and yellow wire at 58 are non existent and there are no white plugs there to indicate that it might have been like that from the factory.
I guess next on the list is to contact the person that did my harness and find out whether he removed this on purpose or if it was missing when he got the harness.
I have tracked down a couple of O2 sensor pig tails on the net.
If I can just track down the terminals that fit the ECU plug then I can add the plug back to the harness.
I have a feeling I am going to end up buying a Bentley manual for the donor car as well so I can make sure that I have the wiring right.
Probably not a bad idea to have one anyway and if I had one now I probably would have figured this out already.
_________________
Pretty normal daily driver build
https://www.thesamba.com/vw/forum/viewtopic.php?t=708418&highlight=
4x4 build
https://www.expeditionportal.com/forum/threads/volkswagen-vanagon-4x4-conversion.162055/ |
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uberaudi
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Joined: June 24, 2013
Posts: 503
Location: Hi-top Country
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| Posted: Wed Apr 22, 2020 8:41 pm Post subject: Re: Another Simple Question - Name That ABA Plug |
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The front and rear o2 sensors have slightly different plug connections but are essentially the same. I ordered the wrong one by mistake (the brown plug style) but then remedied that by cutting off that skinny rectangular boss with some snips. It slipped right in to the harness connecter and works fine.
Edit: I suppose I should add that I am only running one o2 sensor on my OBD2 swap and no cat.
Last edited by uberaudi on Wed Apr 22, 2020 8:46 pm; edited 1 time in total |
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Vanagon Nut
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Posts: 10379
Location: Sunshine Coast B.C.
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| Posted: Wed Apr 22, 2020 8:45 pm Post subject: Re: Another Simple Question - Name That ABA Plug |
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| vwhammer wrote: |
I have the brown wire (actually mine is brown and white) coming from the sensor plug that runs to pin 12 on the main ECU plug.
I have the white wire that runs to pin 20 and the yellow that runs to pin 42 all as the pinout list says.
There is also an extra red and white wire on the sensor plug that runs to a relay that was supplied in the harness.
Well I don't know that it is "extra" but its just not noted in the pinout list because it does not go to the ECU plug.
Now if I move on to O2 sensor #2 it seems that all the wires have been removed from the harness.
If you look at the back of the ECU plug you can see that the holes that were not used from the factory have some kind of white plug in them.
If I trace the wires that would have gone from the ecu plug to the #2 O2 sensor it seems that they were all removed.
There is no red and white wire at pin 13 and there is no white plug there either.
The brown wire at 66 and the white or black and yellow wire at 58 are non existent and there are no white plugs there to indicate that it might have been like that from the factory.
I guess next on the list is to contact the person that did my harness and find out whether he removed this on purpose or if it was missing when he got the harness.
Probably not a bad idea to have one anyway and if I had one now I probably would have figured this out already. |
I really should crack open my Bentley and look at the diagrams but from memory....
The relay in question is usually referred to as the HO2S relay. It is for controlling the heater on the #1 O2 sensor. (I'd guess that the O2 sensor #2 does not have or require a heater). edit: I see a heater control wire at ECU 66 for the #2 O2. end edit. ECU 12 controls the HO2S relay by "supplying" (switching) a ground to it on and off. The red/white "extra" wire should trace back to a switched 12 volt supply. e.g. most likely to a wire labelled "ignition switch 15" or 'black wire, round connector 7a' or it would trace back to a junction that connects to same.
Contacting the harness guy would make sense but as I speculated prior or in another post, it's quite possible that under OBD2 Motronic in a Vanagon, a post cat sensor is not really needed. i.e. at worst, if the OBD sensed a missing #2 O2 sensor, at worst it might only store a DTC for that; it may not even light up the MIL. As another example of stuff that most likely is not needed, the VSS. i.e. I bet your harness does not have a VSS plug either. And, the same DTC thing may apply to that. BUT.....
I'm just some guy listening to David Sanborn, drinking beer, typing away, so caveat emptor!
PS. assuming you don't need that pesky #2 O2 sensor, if you're mounting the ECU in the engine bay or somewhere where moisture might get at it, can't hurt to plug the unused wire holes at ECU connector.
Neil.
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1981 Westy DIY 15º ABA
1988 West DIY 50º ABA
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vwhammer
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uberaudi
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| Posted: Wed Apr 22, 2020 9:06 pm Post subject: Re: Another Simple Question - Name That ABA Plug |
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| Who did your harness? TDC Shop did mine and it's great! |
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dkoesyncro
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Joined: December 10, 2006
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| Posted: Wed Apr 22, 2020 9:12 pm Post subject: Re: Another Simple Question - Name That ABA Plug |
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The motronic system only needs few inputs to run, it's also archaic but adaptable. IMO, the motronic obd2 system is like the good old days of farfegnugen, simple and dependable!
I have the Bentley, I'm happy to share the schematics or help anyway I can. Niel has also done a fair amount of ABA and is of great value. You're in good hands here- |
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vwhammer
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