2004 Jetta TDI (9M) 280K miles. New HEX-V2 cant connect to 01-Engine

   #21  

Trifecta

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I disconnected 46-Central Conv. (after also throwing on the battery charger). Still no comms with 01-Engine. Thank you, though, worth a shot.

That the two times in your career that you saw this issue and it turned out NOT to be the ECU gives me pause. I would hate to replace the dang ECU and still be in the same boat.
 
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Fred's Imports

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I've never replaced an ECM on that model but it is cheap and easy to do if you have the security code.
 
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Uwe

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In order to see if a replacement ECU will solve the problem, he doesn't need to match it to the car; he just needs to plug it in in place of the existing ECU and see if he can talk to it consistently/reliably. I suspect that's doable without so much as removing the existing ECU from its mounting.

If a replacement ECU doesn't talk either, then the problem is elsewhere and there's little point in jumping through the hoops required to match it to the car's immo.

-Uwe-
 
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All very encouraging. Diving in.
 
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New ECU procured. After checking with local locksmiths about retrieving PINs (low knowledge/high $$), I opted for an immo-defeated unit at a reasonable price. That turned out well, in that the car starts, runs fine, not so much as a MIL.

However... still cant connect to 01-Engine with either Legacy Cable or OBD2 reader. Connects to all other controllers.

It looks from the wiring diagram that after the ECU the next connector is that orange T10 in the plenum chamber... Is my next best step to traceback and validate the wiring from ECU to Cluster? It has been garaged most of its life and I see zero signs of water ingress at the plenum rain cover on casual inspection. I don't think thats it, but...

sigh.
 
   #26  

Uwe

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Is my next best step to traceback and validate the wiring from ECU to Cluster?
I would think so. I mean, you've pretty much determined that the problem isn't the ECU itself, and you have comms to the Cluster, and you've done the K<->W jumper, so what else can it be?

-Uwe-
 
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Well, I am whistling in the dark hoping there might be other k-line interference, or grounds, or somesuch that folks with actual experience may have seen :thanks: But with the way this car isolates the ECU with that W-Line setup, indeed what else could it be?

Diving back in...
 
   #28  

Trifecta

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No continuity in the W-Line between T94/72 (ECU Connector) and T10/1 (Orange, in plenum) was indeed the culprit. Very fortunately, the issue is not IN the connectors, and a proper wire run between two nice, neat splices behind each connector did the trick. Legacy Cable, and OBD2 reader, and HEX-V2 are go!

Looking for an emoji representing a stream of jubilant victorious cuss-words and coming up short.

Way back when, the presenting issue in this thread was that VCDS-Lite/CheapoBlueCable was connecting with 01-Engine when VCDS/Hv2 was not. I will test all of this with some rigor and post my findings.

THANKS FOR YOUR SUPPORT!
 
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   #29  

Uwe

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Way back when, the presenting issue in this thread was that VCDS-Lite/CheapoBlueCable was connecting with 01-Engine when VCDS/Hv2 was not.
I'll speculate that it was coincidence. Intermittent break in the wire that just got worse with time..?

-Uwe-
 
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Trifecta

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^ No doubt.
I A-B tested the two cables multiple times in a single session (multiple times). Perhaps in those last sessions before it failed completely there was just not quite enough flow to support the Hv2 and the others baaaarely worked. But yeah, I suspect Hv2 will be just fine going forward. :thumbs:
 
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