T87 Swaps

[kidturbo]

Is it just me or anyone else seeing a pattern here with GM replicating pulses?? They did it with the FICM, and they did it with VSS signals. Like the started with a manual transmission that didn't have a TCM, then when added the TCM, forgot the ECM needed to know the speed too. So, lets pass it a pulse over "1" wire, and whatever it's will be happy. When they could have just sent it over CANbus, which they do on some later stuff. I've now thoroughly confused myself..

If we need a pulse, It can be generated from CANbus data supplied by the TCM, or we can read in the VR pulse signals, invert to Hall, and grab a signal there to Convert to the 100k per mile or whatever the ECM wants to see. Not a biggie, just more bench testing. Also belive Ross added the ability to pick which type of VSS your ECM wishes to use, in a recent release.

 

[Baddiode]

That is exactly what I was thinkg a few days back when I posted about verifying the VSS pins on the 17+ gassers. They ran it to the ECM same as many older ECM's had.. IE the E35A/B, E38, LLY... And if the physical pins or CANbus is used, is a single bit in the bin file... Thanks so much. Answers that question. LOL

Post up that diagram when you get a min please. Also check the 10 LMM trucks. I was thinking it was T' in harness, and might also explain why I was not seeing a VSS on the E35B ECM. Yet I was seeing it on the TCM data when emulating a signal.

If so, the VR to hall inverter is gonna be the best solution, as it covers both requirements across the years.

I just dug through any 2010 lmm wiring and pinouts and cant find anything showing the vss on the tailshaft going to anything other than the tcm. There is a vss wire coming from the ecm to the ebcm for traction control use and isnt in the schematics on the non traction control trucks. There is a VSS high input on the ecm x2 plug at pin 45 but the only place i can find that wiring is on a kodiac with a manual transmission, which makes sense as that wouldnt have a tcm to relay vehicle speed. Maybe if the ecm doesnt think the engine is running it simply is ignoring the canbus message for speed from the tcm and only using wheel speed data from the ebcm? I do know if the tcm goes out on these trucks while going down the road, the ipc will still show speed but i would assume thats coming from the ebcm since the vss only appears to the connected to the tcm. If i go back further i do see where the vss runs to the older lly trucks ecm but those also had a completely different tcm then the A40/50/T14 and looks like the ecm is relaying the vss to the tcm and not the other way around in those years. Also here are the 2017 3 speed sensors in the 8 speed trans and the component view showing they are inside the transmission itself.

Have to correct myself here so it isnt the early lly that has vss to the ecm from the vss on the tailshaft it is the lb7. But now that i look back it seems it got discussed anyways i just missed it. It also seems pin 25 on the a40/a50/t14 module is a vss relay, sending a single feed vss pulse "replicated TOS:transmission output speed" that is just a copy of the vss high input instead of just sending it over the canbus unless its in case the tcm fails which makes me think maybe pins 25 and 60 are just internally connected and the ecm doesnt need to supply ground reference since its already given by the tcm. Takes away my idea that maybe the ecm uses the ebcm for speed in a tcm failure. @kidturbo im not sure what you are referring to with Ross adding the ability to pick VSS type for ECM? What am i missing here?

 

[Cougar281]

Yet all of those ECM's have VSS High and Low do they not?

Been a while, but I refuse to cheat myself by looking up the actual schematics... Yet I totally agree on the VSS Hi being the active input on all.. LOL

They do... HOWEVER, in the Automatic/Allison configuration, according to the wiring diagrams, the VSS input pins connect to the TCM. They only go to the sensor in a manual trans config.

 

[Baddiode]

They do... HOWEVER, in the Automatic/Allison configuration, according to the wiring diagrams, the VSS input pins connect to the TCM. They only go to the sensor in a manual trans config.

That was exactly what I was seeing. Which pretty much tells you that the replicated speed from the tcm is the same 40 pulse per revolution signal that the sensor is sending. In fact I looked at manual trans ecm tune and it is still set to 40 pulse per revolution on the speedometer table and the low reference pin on the ecm just isn’t connected on an Allison truck where it’s connected to the vss on a manual truck. So at least we know nothing changes the tcm just passes the vss signal on through to the ecm. Now here is a funny thing though…… so on my 2010 after being awake all night listening to the wind I was able to find a vss flow sheet on SI. On my 2010 the vss flow goes VSS—tcm—ecm—ebcm—navigation system/radio. So it gets passed through 3 modules before landing at its destination of the radio for sound speed control smh. Seems overkill for what could be a single canbus line for vehicle speed. Talk about dropping the ball then kicking it every time you try to pick it up

 

[Cougar281]

Well, like you kind of said, it's like they designed it around a manual truck and then were like 'oops... this needs to work right with a TCM for an auto trans there...' and that's what they came up with. They could have had the VSS go to the ECM and then the ECM spits that data out on the CANBUS, but maybe the Allison coding was like 'nope, not doing that' so they had to adjust. OR... back in the 2005 and back days, the ECM was actually a PCM that controlled the trans and the engine for the gassers, where the VSS did go to the PCM, but the Duramax was always an ECM/TCM combo right from the start.

 

[Baddiode]

Well, like you kind of said, it's like they designed it around a manual truck and then were like 'oops... this needs to work right with a TCM for an auto trans there...' and that's what they came up with. They could have had the VSS go to the ECM and then the ECM spits that data out on the CANBUS, but maybe the Allison coding was like 'nope, not doing that' so they had to adjust. OR... back in the 2005 and back days, the ECM was actually a PCM that controlled the trans and the engine for the gassers, where the VSS did go to the PCM, but the Duramax was always an ECM/TCM combo right from the start.

Right because Allison had their own transmission control module and gm had to make it work with their pcm. I think that’s where gm first realized how much more efficient the ocm was when it only had one task and not 2. But aside from that from what I found it seems there could be a very simple solution. Jump the vss over to the ecm like the manual trucks are hooked up and just tap the signal with a converter to convert signal for the t87. Could simply connect the vss high to the TOS wire and run a single ground reference wire from the ecm. Seems like that would fix the vss problem if we can grab and convert the signal.

 

[kidturbo]

Great work guys. Glad we can finally get this ironed out, so I have someone to ask next time I forget where we left all these answers...


If ya search VSS on here, or the EFI forum, you'll find where I hit on each of these ECM options over the years. Going back to first hooking up a VSS pulse into the OG LLY boat. When moving to the LBZ/LMM's stand alone, it was all about finding a Std Transmission OS so the ECM would read the 40 pulse raw, and not just speed over CANbus. Then as other swappers started hitting on this problem, Ross took interest and started digging into the OS models to find the switches. And according to this latest release E38 Speedo Options, we also have multiple CAN tagged options too.. Who wants to clarify these, as I don't reconize the Early/Late terms he's using, but gaurantee they are relevant also..

 

[Baddiode]

Great work guys. Glad we can finally get this ironed out, so I have someone to ask next time I forget where we left all these answers...


If ya search VSS on here, or the EFI forum, you'll find where I hit on each of these ECM options over the years. Going back to first hooking up a VSS pulse into the OG LLY boat. When moving to the LBZ/LMM's stand alone, it was all about finding a Std Transmission OS so the ECM would read the 40 pulse raw, and not just speed over CANbus. Then as other swappers started hitting on this problem, Ross took interest and started digging into the OS models to find the switches. And according to this latest release E38 Speedo Options, we also have multiple CAN tagged options too.. Who wants to clarify these, as I don't reconize the Early/Late terms he's using, but gaurantee they are relevant also..

View attachment 120835

If I recall right the early up through 07 or 08 had an early hybrid type canbus but the 09 for sure had the same can bus as the 07.5-up trucks. Have to look up years but I know that a 2009 Chevy express van has the e38 and new canbus I will do some digging and see what it shows when I bring up different tunes I have. I have a few express van tunes

 

[kidturbo]

I pulled up my running LMM config, and while EFI update has the switches for the E38, I don't see it in the E35B release. However somewhere I have a CAX file saved to change between CANbus and VSS Hi as the input options. Not really relevant for this endeavor, but at least we know it's in the mix. But I did find this comment in his options to be relevant.

Minimum vehicle speed before the ECM will obey a GMLAN request (from BCM etc) to limit vehicle speed.

 

[Baddiode]

I pulled up my running LMM config, and while EFI update has the switches for the E38, I don't see it in the E35B release. However somewhere I have a CAX file saved to change between CANbus and VSS Hi as the input options. Not really relevant for this endeavor, but at least we know it's in the mix. But I did find this comment in his options to be relevant.

Minimum vehicle speed before the ECM will obey a GMLAN request (from BCM etc) to limit vehicle speed.

View attachment 120839

If we can turn on canbus vss on the lmm would that not receive vss from the t87 tcm then since with the duramax calibration in the t87 it is sending out a canbus vss to the ecm? The 15.5 duramax lml has the vss tail shaft sensor connected to the tcm unlike the gas where it goes to the ecm. The duramax calibration sends vss via canbus to the ecm so if we could enable the 35b lmm to receive vss via canbus would it not work?

 

[kidturbo]

LMM is GMLAN only by default. I'm 99% positive of this on the light duty trucks at least.

Sent from my SM-S901U using Tapatalk

 

[kidturbo]

Follow up to last, as was walking and typing..

By default I'm pretty certain that the LMM ECM uses only the CANbus data for all relevant tables. I can verify this on the bench in a few. But right now the tune I have loaded on bench unit is one of my all cax'd out stand alone versions from boat testing.

I've previously fed the ECM an emulated PWM style VSS and it while it would register a speed, the limiters would not respond in the tune. IE 4x4 Low Tables. Yet when I hooked up a T42 to datalog with, I triggered the default 158kmh limits at around 60mph becasue my driveshaft speed was exceeding the 40 x 3.72 x tire size caulation in the running ECM tune. That's why I know reads the pulse per rev output shaft sent over CAN, and doesn't rely on an actual Vehicle Speed being calcualted by our TCM ratios. ECM wants it's own Pulses..

Now to wire it all up, and try with and without feeding the ECM a PWM, or Hall Effect signal on that VSS line... Gonna have to go find that 2012 thread and see what the LLY prefered.

 

[kidturbo]

Found my notes on this topic. Stuck em somewhere I couldn't lose em.

LMM OS 12628594 (NQG) Option

Hi All, looking for some better details about this Engine Operation version 12628777. It's from a floor shift transfer case truck, and changes the operation of pins X-1 57 & 82 . Been playing with both versions, and the difference is how the ECM selects Torque Reference Tables under A, B, and...

forum.efilive.com

Last post seems to be where I stopped, Squirrel...

 

[Baddiode]

Found my notes on this topic. Stuck em somewhere I couldn't lose em.

LMM OS 12628594 (NQG) Option

Hi All, looking for some better details about this Engine Operation version 12628777. It's from a floor shift transfer case truck, and changes the operation of pins X-1 57 & 82 . Been playing with both versions, and the difference is how the ECM selects Torque Reference Tables under A, B, and...

forum.efilive.com

Last post seems to be where I stopped, Squirrel...

That dang squirrel gets me sometimes too. So are you saying that the lmm ecm wants the vss pulses but uses it on a limited basis but uses can vss data? Sorry I think I may have misunderstood what you were saying. I’ve had some time to look at different tunes today and see where with the t43 6 speed you can actually switch between canbus and tos output which I have pinned the plug at the trans and used it with tos active on a 6l80 swap into a 2006 ls1b Sierra 6.0. I have to think that maybe one of the unused pins on the t87 is possibly able to be enabled as a tos output but so far have not been able to find any vehicles with the t87 and tos unfortunately but still digging hoping i find one.

 

[kidturbo]

I'm thinking the TOS is "Depreciated" as they like to tag it in some other protocols. The LMM uses the TOS as some possible reference to the high speed GMLAN messages it's getting from the TCM.

I just finished verifying some canbus related hacks to the gasser OS. Now going to get the input/output emulator up and running on that OS first. Then will reload the Allison OS and along with my E35B runing where we can sort this VSS line or CANbus question on at least 1 OS version.

 

[Baddiode]

I'm thinking the TOS is "Depreciated" as they like to tag it in some other protocols. The LMM uses the TOS as some possible reference to the high speed GMLAN messages it's getting from the TCM.

I just finished verifying some canbus related hacks to the gasser OS. Now going to get the input/output emulator up and running on that OS first. Then will reload the Allison OS and along with my E35B runing where we can sort this VSS line or CANbus question on at least 1 OS version.

That makes more sense.
I just got to a point I was a little tired of searches and schematics and decided to plug my hptuners into the t87 and found out that unlike efi, hp actually has all the dtc populated. Otherwise didn’t see anything there that isn’t in efi. So with that at least if we can get things to communicate and still get an unexplained fault I can always set it to not report said code especially say the pressure control solenoid that my 2010 doesn’t have.

 

[Cougar281]

So something I noticed on the pinout chart I made to figure out what pin on the A40/A50/T14 needs to go to what pin on the T87 that may be a problem or may not - I think what is the line pressure control solenoid on pin 2 of the T87, which the LMLs got but the LBZ/LMM didn't have, I listed as going to pin 74 on the A40/A50, which is the 'mainline pressure solenoid control', which I'm 98% certain is the 'G' solenoid, which we don't actually need. In the calibration for the '15 LML, there are D5179-D5182, which are for 'Mod Main Pressure (G-Sol)'... Since we don't actually need the G Solenoid, and don't have the mainline pressure solenoid, I wonder if connecting it that way and setting the values to that which will prevent it from ever being allowed to be enabled?

 

[kidturbo]

If I can ever get my hands on a LML year valve body for the bench, I could add some type of input on that. But for now, we gonna have to go with your best guesstimate..

 

[kidturbo]

Ok so I loaded the Allison tune back into the T87 and connected to my E35B on the bench. Running the same tune file with speed limit disabled. I set the Engine Emulator RPM up around 2500R, and ran the Output Speed Sensor emulator all the way up to 8000Rpm. Noted zero change to fueling data.

Then I loaded a tune file with factory speed limiters and repeated the tests. This time as I exceeded the 3000RPM on output shaft, the ECM pulled all fueling, and injectors stopped firing. See the pics below So that tells us the ECM uses output pulse via GMLAN data for our speed related tables. However, if you look at the logs below, the VSS signal as logged by the ECM is always 0..

Now I'm going to dig out the ECM VSS wire and add it to our 40 pulse signal. I'll bet it reads a speed... Is it important? Yet to be seen..

Below 158km/h



Above 158km/h

 

[kidturbo]

Ok kids I just ran out of Caffeine, but solved it. And luck have it, with results in our LMM/LBZ favor...

I reset the speed limit in the LMM ECM to 80km/h. Which should reflect as fuel cut at a much lower output shaft rpm. Tested it, and now cuts the fuel around 2000rpm. Which verifies the ECM speed limit tables are actually using the VSS raw pulse data supplied by TCM over GMLAN.


Next I wanted to test the VSS High signal wire to the J2 45 pin on the ECM. So I connected it to our Arduino emulator that supplying the 5v pulse to our TCM inputs. I left the TCM off, and the ECM picked up the 40 pulse correctly as a 5v square wave.. GOOD SIGN..

So with our engine spinning 1250rpm, and fuel injectors hammering away in the background, I spun the output shaft speed up to what read 200km/h. And guess what, no fuel cut via VSS single wire only.. It's not interested in the pin 45 signal.. Also a good sign.



Last I connected powered up the TCM, and the emulator is now feeding 40 pulse per rev signal to the TCM turbine speed line, output speed line, and the TOS / VSS High pin on our LMM ECM. Some freaking way, everyone is happy receiving a emulated 5v pulse, AND the CANbus and TOS speeds all match up in the data.. Super news...

So I cranked the speedo POTs up, and soon as output shaft RPM hit 2000, the ECM VSS singal crossed 80kmh, and the ECM cut the fuel. The lack of pecking in my ears confirmed the data below.



Everybody happy with the same 40 pulse per rev 5v Square wave. So we can easily Tee off our Hall converted T87 output sensor signal line, and fill that TOS hole in the old connector @Cougar281..