2014 6.0 L96 With a 6l90 Communication Issue

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I have an L96 paired with a 6L90 from a 2014 Express van. They both came from the same unit, along with the E38 ECM. The data bus is unstable and disconnects when using VCM Scanner but will not load with VCM Editor. If I remove the TCM connector from the transmission and Install a 120-ohm resistor between pins 10 and 11 at the transmission connector, I can communicate with the engine. I removed the VATS and wrote back to the E38 with the transmission removed from the data bus. However, when I reconnect the transmission, the data bus becomes unstable. I tied my OBD port into the can between the TCM and ECM from pins 27 and 28 on J1 at the ECM. Pins 27 and 28 of J1 are connected to the Trans on pins 10 & 11. I don't believe the transmission communicates, as the speedometer shows 158mph when I can connect to the ECM. Any help would be greatly appreciated.

[mister480v]

If you ohm CAN low and CAN high you should get 60 ohms. If you don't, start disconnecting CAN devices until the status changes. I bought a cheap 50 dollar oscilloscope because of this exact problem with my 03 silverado, except that predates CAN bus. My issue was class 2 serial data, but operates on a similar principle. I couldn't write to the ecm successfully unless i tried about 20 times in a row. Turned out the door lock module was gumming up the network. Enovation controls has a good you tube video on diagnosing CAN bus. If you have a decent multimeter you can check the voltages of CAN high and CAN low to make sure they're in spec. I wanna say CAN high is a max of 7 volts and CAN low is like 2.5 or so. Something like that. Also double check the trans is getting accessory power. Mine randomly lost power and they had to run another wire because nobody could figure out why the wire went dead. That also caused me issues with the data bus.

[[email protected]]

Thank you for the advice mister480v. I found that I had the can pinned wrong at the TCM and was able to get everything working. I now have a new issue. The engine is hard to start and will not idle when it does. I am sure the VATS are disabled and have fuel pressure. I have the MAF sensor just hanging in front of the intake throttle valve, as I don't have any plumbing yet. I created a data log of the engine cranking and stalling and will attach it. I have never worked with an LS but have done numerous engine builds and am now questioning if I have the cam timing out. If it were SBC, that would have been my first guess. Engine Hard to Start - Will not idle.hpl

[GHuggins]

Try failing the MAF in the calibration and cranking. Hanging in front of won't read air.

[[email protected]]

So that I understand completely. To fail the MAF i would calibrate the Airflow vs Freq by setting 0 in the first box and something like 12 in the rest of the HZ range?

[GHuggins]

Don't mess with the MAF curve. Under engine diagnostics - airflow - set fail high to 0 - then set the rpm for test to 1 - seconds to fail .1 and dtc's (102,103) to fail on first error.

[[email protected]]

So, I was able to make the changes you suggested, and it did start and idle for about 5 seconds. I was feeling optimistic, and then it stalled. It smelled flooded and would not restart after it stalled. The engine logged a fault for the MAF this time. I need to find some intake tubing to install the MAF properly and retest. Does that make sense to you? Thank you for the advice/help!

[GHuggins]

As long as the engine is stock and unmodified it should run on the stock fuel and VE tables. Set all MAF dtc's to first error including the 101 just in case for whatever reason it somehow kicked it back. With those fail settings it should fail with initial cranking, which sounds like it did, it just for whatever reason went back or flooded out. I assume full throttle didn't re-fire like trying to put it into clear flood mode? Now I've only ever seen this a couple of times, but if it fires and runs for a few seconds then floods out and dies it's possibly a bad O2 that is shorted, but the mv readings will show that if it is with key on engine off. A False reading there will cause fuel to get dumped and stall the motor. Usually only happens on small displacement engines though.

[[email protected]]

OK, I could not run it by creating the MAF fault. However, I have replaced the MAF sensor, and the engine will idle roughly. I put the original tune back in the ECM, so I now have faults for both rear o2 sensors. I have attached a short log file. Any thoughts on what I am missing?Engine Runs Rough - New MAF - 1.2.24 Short.hpl

[GHuggins]

At this point it just looks like fuel and airflow are off. You need to get the exhaust and intake hooked up to it and tune it in. In that log it's holding the throttle really open due to min air being too high or fueling being off. Idle timing is low because of that. It can't correct fuel because no O2's for trim correction and no wideband to know how lean it is. Finish the install then go from there.

[[email protected]]

Thank you, I will and see what it does once it has something past the headers.