Canbus VNT turbo

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87e30
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Canbus VNT turbo

Postby 87e30 » Wed Mar 09, 2016 4:07 pm

Obviously not e30 related, but does anyone have experience with VNT turbos in a canbus vehicle? I'm working on our 2008 UD 2000 that won't go over 2000 RPM. Getting error code U1123 (among others) that says "Communication disruption (VNT)". The VNT actuator does not move at all when the ignition key is turned on like it does on all of our other trucks. There are 4 pins in the 6 pin connector plugged into the VNT. 2 are getting ground, 1 is getting around 2.9v and the other is getting about 1.7v. I don't know if these voltages are correct. I've never messed with anything canbus before.

I do know the turbo that got replaced was all gummed up inside and the VNT actuator had trouble moving. We swapped in a newly rebuilt turbo, and no movement of the VNT at all. Plugged in a known working VNT and still no movement. There's obviously some kind of communication error somewhere, but I have no idea where to look. Other OBD errors we're getting are U1122 (Communication disruption (EGR)), P0102 (MAF meter malfunction "low"), P2002 (DPF system malfunction), and P2103 (Electronic control throttle open circuit).
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Arktisblau 5-speed 86 325e (current DD)
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Re: Canbus VNT turbo

Postby Yoshi » Wed Mar 09, 2016 6:58 pm

This must be what my wife feels like when I talk cars to her. I have no idea man.
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Re: Canbus VNT turbo

Postby 87e30 » Wed Mar 09, 2016 10:28 pm

And all this time I thought you were the all knowing! :-P lol

I have everyone I talk to completely stumped. I've talked to Garrett distributors and rebuilders, diesel truck shops, etc. I just need to know how the VNT and EGR communicate with the ECU. When I use the computer to send position commands for the VNT or the EGR it says the commands were sent successfully, but neither one moves. Also when watching the data stream, even if I move either one manually, the position always reads 0%, and air flow always reads 0. We swapped in another MAF too and no change.
Attachments
08UD2000 VNT DTC.jpg
08UD2000 VNT DTC.jpg (74.07 KiB) Viewed 1277 times
08UD2000 VNT Data stream.jpg
08UD2000 VNT Data stream.jpg (109.8 KiB) Viewed 1277 times
Schwarz 5-speed 87 325is (newest project)
Arktisblau 5-speed 86 325e (current DD)
Schwarz 5-speed 87 325e (parts car/LS1 swap?)
Gazellenbeige automatic 85 318i (70,000 miles)
Alpine white 5-speed 87 325is (my first e30, possibly for sale)
99 Suburban
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Re: Canbus VNT turbo

Postby M20_fever » Fri Mar 11, 2016 4:50 pm

Did you replace the EGR and Turbo at the same time? Are the firmware versions for the new parts the same as the vehicle network?
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Re: Canbus VNT turbo

Postby 87e30 » Sat Mar 12, 2016 4:20 am

Well I don't know what the ORIGINAL problem was, but I fixed it yesterday. Yes, the EGR and turbo were both replaced at the same time. When we put everything back together I know the turbo VNT was not working. It's supposed to move as soon as you turn the key. I'm not sure about the EGR at that time. Of course one of my first troubleshooting steps for the electric actuator was to check all of the fuses and relays. Everything was fine. Spent a few days laying on the dirty ground under the truck checking and rechecking every wire, sensor, and connector, removing each one and blasting with electronics cleaner before reconnecting firmly. I did find 1 loose connector on a sensor. That shouldn't have had anything to do with the problem though. Everything seemed fine.

Yesterday our other 2008 UD 2000 was actually at the shop so I could get under that one to do some research. Found +12 on a wire (that was grounded on the broken truck) that when traced back changed into an orange wire with silver spots. I found 2 orange with silver spot wires (same color as the wire that supplies power to the EGR) connected to the ECU. Neither one had voltage. The schematics say those wires are both "+BF", whatever that means. I disconnected the 2 connectors that had those wires from the ECU and put +12 to one of them and I heard the VNT move! +12 to the other wire and same thing. I couldn't hear it, but the EGR moved too. I manually moved it each time, and after I put power to either of those wires it would move back to where it had been.

So at this point I'm thinking maybe the ECU is bad because it's not putting out +12 on those wires like it seemed it was supposed to do. I was just about to rip the ECU out of the other truck and test it (which would have caused other problems because each injector has a canbus serial number that needs to be programmed into the ECU before it'll work), but decided to go over all of the fuses and relays again. Damn 10 amp engine control fuse popped. Threw another one in there and everything is happy!

So to make a long story short. It originally was most likely a loose connector somewhere, and I probably popped the fuse while testing, then when I reseated all the connectors it would have worked. Whatever, it's fixed.

But in all of my troubleshooting I turned off the "marine grade" waterproof 80 amp breaker on the PTO control and the breaker broke. The terminals are corroded to shit, but it looks like too much water got into the waterproof breaker and when I tripped it I couldn't get it to reset. Can't find our spares so waiting on some new ones from eBay.

I've put in 67 hours already this week, why the hell am I still at work? Screw you guys, I'm going home! </Cartman>
Schwarz 5-speed 87 325is (newest project)
Arktisblau 5-speed 86 325e (current DD)
Schwarz 5-speed 87 325e (parts car/LS1 swap?)
Gazellenbeige automatic 85 318i (70,000 miles)
Alpine white 5-speed 87 325is (my first e30, possibly for sale)
99 Suburban
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87e30
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Re: Canbus VNT turbo

Postby 87e30 » Sat Mar 12, 2016 4:26 am

On the plus side, I learned a shitload about canbus from this whole ordeal. lol
Schwarz 5-speed 87 325is (newest project)
Arktisblau 5-speed 86 325e (current DD)
Schwarz 5-speed 87 325e (parts car/LS1 swap?)
Gazellenbeige automatic 85 318i (70,000 miles)
Alpine white 5-speed 87 325is (my first e30, possibly for sale)
99 Suburban
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Yoshi
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Re: Canbus VNT turbo

Postby Yoshi » Sat Mar 12, 2016 12:47 pm

It's always something like that. You're like "It HAS to be this major thing" when really it's that you forgot one wire somewhere. I feel you man. It's done now. You may rest.
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Status: HG repair. 488wtq though!

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