No crank 6L80 TCM question

[Phestezio]

Trying to get my project running. Its a sprinter van with a 5.3 swap out of a 2011 silverado. I used everything out of the donor truck and removed any wires I didn't need, mostly from the interior harness. Only thing I removed from the engine harness was the purge valve, VVT and DOD since I rebuilt the engine and put a cam in. I also removed the FSCM and its related sensors and ran a fuel pump relay and mechanical regulator. Was alot easier to run the fuel this way with the sprinter tank. I moved the terminating resistor for the CAN bus from the FSCM connector to the ABS connector to keep the CAN bus intact. I did get a Jasper reman 6L80 and I know the TCM needs to be programmed still.

I went to try to crank it for the first time today and I have no crank. I can see that the BCM is seeing the crank signal from the ignition switch with my scanner but the PCM never gives a starter command. Only code I have that could be the issue is the lost communications with TCM code in the PCM and the TCM not programmed code in the TCM. I can communicate with the TCM with my scanner and I have no CAN bus codes in any module. Also noticed that the gear indicator is not showing park.

Could be a dumb question but I couldn't find a definite answer. Does the 6L80 TCM need to be programmed or written before it will send gear position data onto the CAN bus? If so then that would probably be the answer to my no crank haha.

[blindsquirrel]

I'm not sure it would be a great idea to run the engine with an unknown/no calibration in the trans.

[Estep40511]

Trying to get my project running. Its a sprinter van with a 5.3 swap out of a 2011 silverado. I used everything out of the donor truck and removed any wires I didn't need, mostly from the interior harness. Only thing I removed from the engine harness was the purge valve, VVT and DOD since I rebuilt the engine and put a cam in. I also removed the FSCM and its related sensors and ran a fuel pump relay and mechanical regulator. Was alot easier to run the fuel this way with the sprinter tank. I moved the terminating resistor for the CAN bus from the FSCM connector to the ABS connector to keep the CAN bus intact. I did get a Jasper reman 6L80 and I know the TCM needs to be programmed still.

I went to try to crank it for the first time today and I have no crank. I can see that the BCM is seeing the crank signal from the ignition switch with my scanner but the PCM never gives a starter command. Only code I have that could be the issue is the lost communications with TCM code in the PCM and the TCM not programmed code in the TCM. I can communicate with the TCM with my scanner and I have no CAN bus codes in any module. Also noticed that the gear indicator is not showing park.

Could be a dumb question but I couldn't find a definite answer. Does the 6L80 TCM need to be programmed or written before it will send gear position data onto the CAN bus? If so then that would probably be the answer to my no crank haha.

Something is wrong with the communication somewhere. If its not showing park, its not seeing the PNP switch on the shift shaft in trans. what kind of shift cable did you use? And on your data, if you move shifter, does gear selection change?

[CarlTrans]

No. Also if you got a jasper transmission aren't they supposed to send a program with it?

[Phestezio]

A bit of an update. I did a quick check on the CAN bus. I did not scope it but with a quick meter check I have 2.3v on CAN LO and 2.7v on CAN HI and a resistance of about 58ohms. It seems like the integrity of the bus is intact. Also double checked the gear position wire going from the TCM to the PCM (org/blk wire on X1-1) and it had continuity. I looked at PCM data and the PCM displays P/N and in gear when I move the shifter so it seems the PCM is getting the P/N signal.

The PRNDL is an output function of the BCM though and should be CAN data from the TCM. So at this point i'm thinking the BCM is never sending the start request to the PCM because the BCM can't see the gear position. I did some research and found quite a few instances of these trucks no crank when it not displaying PRNDL. But I do not have a PID in my BCM or Instrument Panel data that shows me gear position, so I have no way to confirm what the BCM sees and just speculating. I am fairly confident that if I can get it to display PRNDL then it is going to crank. Why its not displaying though is now the question. Not sure if its just a programming/configuration issue at this point.

It is a Jasper and i'm sure it has some sort of programming already done to it so they can test it at the factory. But what exactly they put on the TCM is unknown and it does come with a giant sticker saying it needs to be programmed before driving. Only other difference is the trans that I took out was a 4WD version and the one I bought is a 2WD version but they were both 6L80. At this point I think my goal is to get it to display PRNDL and it should crank

[blindsquirrel]

Why would you think it's got everything it needs to work with your specific application, before it's been programmed with the right calibration? Whatever you decide to do, trying to diagnose anything before it's programmed is a giant waste of time.

[ecir55]

Phestezio check your messages on the sprinter forum.

[Phestezio]

Why would you think it's got everything it needs to work with your specific application, before it's been programmed with the right calibration? Whatever you decide to do, trying to diagnose anything before it's programmed is a giant waste of time.

Its not that I think that it has everything it needs to work since I know it needs to be programmed and its obviously not working haha. But I do not know if not having the TCM programmed on a 2011 silverado would cause a no crank or not display the gear. I can totally see this just being a programming/configuration issue. But I also wanted to check the CAN bus and wiring to make sure it wasn't something I did I.E. removed a wire I needed that could possibly fail the programming before I try it.

Either way it needs to be done and i'm confident now that the TCM can be programmed without failing. But was hoping for a definite answer from someone who possibly deals with 6L80 TCM on a daily basis that it either will or will not cause a no crank no PRNDL if its not programmed. I will probably find out tomorrow whether I get a definite answer before then or not since I have it scheduled to be programmed tomorrow morning/afternoon so I will find out if I get gear indicator and crank after that.

[blindsquirrel]

Do you not have the Silverado stock file? If you do, and it's already licensed, all you have to do is a 'write entire' on the TCM only (uncheck the box for ECM and any other modules).

[Phestezio]

Do you not have the Silverado stock file? If you do, and it's already licensed, all you have to do is a 'write entire' on the TCM only (uncheck the box for ECM and any other modules).

Just to make sure i'm not misunderstanding exactly how the licensing system works with HP tuners. So when you say if its already licensed you are referring to the new TCM correct? I was under the impression that the license was tied to the module itself so I would need to buy another credit for the new TCM before I could write to it.

[blindsquirrel]

https://forum.hptuners.com/showthrea...re-new-license

[blindsquirrel]

If you have a file from the stock truck, and you've already licensed the file, and the file contains both the ECM and TCM, then you can write-entire the TCM portion to a new TCM without costing anything additional.

If you do not already have a stock file, or the file is ECM only (I am unclear on this, because right up front you said 'used everything from the donor vehicle' but then get around to saying the trans came from somewhere else), you would have to find a file from somewhere else pulled from some other vehicle, and then license that, and that's not recommended.

But your file from your vehicle? Yes, can write to different TCMs all day long. Not the ECM, though. Apparently.

[TransGo Robert]

Not sure if this will help since this is a swap and reading all this is a bit over my head, but on a normal 6L80/90 setup the P/N signal from the internal mode switch goes directly to the ECM, the other 4 switches are read by the TEHCM. Programed or not makes no difference, this is a separate circuit that bypass the TEHCM if you want. If the ECM does not see ground on that wire, it will not crank.

[Phestezio]

I see, I knew you could not write to different ECM without another license I just assumed that applied to any module. I did pull a full file of the stock truck before I stripped it down so I do have the original TCM file.

I did a write entire to the TCM using the old file today. That was the issue for no PRNDL but still no crank. Now i'm kind of stumped lol. The only code I have in the BCM that I originally thought could be the issue is U1511 which is for the LIN bus. But I double checked the wiring diagram and PCM pinouts and the PCM is not on the LIN bus so the crank request has to be sent over the CAN bus so I don't think that code is an issue in my situation.

I see the BCM changing from run to crank so I know its getting the signal from the ignition switch. I see the PCM is reading P/N and In Gear when I move the shifter so the dedicated wire between the TEHCM and PCM is connected and working. I have VATS disabled but just for shits and giggles I plugged in the TDM no change. I also disabled starter checks in the PCM and did a write entire, no change. I don't see anything that would be preventing it to crank in the data. Now my question is the BCM even sending out the crank request or is the PCM not doing anything with it.

Not 100% sure if I can swap in a known good BCM without programming it. I do have a couple trucks in my shop that should have the same BCM and need engines so I could swap one of those in just to try if swapping BCM without programming wouldn't cause the same no crank issue. I may try it tomorrow either way, they are easy enough to pull out and plug in

[blindsquirrel]

Disabling starter checks is for when you have a wire going direct from ignition switch to starter solenoid (otherwise, it thinks it is being hotwired). If you're using the switch to request starter activation by the ECM then that shouldn't be turned off.

Diagnose it like it was a 2011 Silverado with a no-crank condition. There are service manuals for that sort of thing.

[Phestezio]

I was not 100% sure exactly what the starter checks was used for. The description in HP tuners was a bit vague but figured I would just try it. So with starter checks turned off in the PCM I should be able to jump the starter relay manually and it should start correct? I will still diag what my no crank issue is using the start request but if I could get it started that way for now that would be cool.

[Phestezio]

Just an update, with the starter checks and starter diag turned off the engine starts and runs when I manually jump the relay like you described. Still not sure why it won't start the way its intended. I looked up the OE test procedure for no crank and went down it with no luck. Everything in the OE procedure either checked out fine or did not apply to my no crank condition. I swapped in a BCM from another truck just to try and no difference but that still isn't a 100% guarantee its not the BCM since I did not program it since it is from a customer vehicle.

I will probably run a second button to trigger the starter relay for now to start it so I can run the van but still be able to keep diagnosing the intended no crank issue but at least I can start tuning for the cam. The tune I have now is basically the stock tune with DOD/VVT disabled and very slight changes. The cam I put in is a towing cam so it is not very wild and fairly similar to the OE cam specs so I figured the stock tune should at least idle and be a decent starting point.

I thank you guys for your help.

[ecir55]

good to hear

[TransGo Robert]

Not 100% sure if I can swap in a known good BCM without programming it. I do have a couple trucks in my shop that should have the same BCM and need engines so I could swap one of those in just to try if swapping BCM without programming wouldn't cause the same no crank issue. I may try it tomorrow either way, they are easy enough to pull out and plug in

There is a PID for the start request from the BMC when you look up the ECM data with a scanner. That PID should tell you if the BCM is the one not sending the request or the ECM refusing to execute it.