LMM (NQG) Tune VS Standard

[kidturbo]

As most of you know I prefer the E35B over the E35A ECM for stand alone swaps. And I thought I knew it pretty well, until I started looking to assign some normally unused signal lines for other uses.

That's when I stumbled onto a pinnout difference between two build version under the same LMM 12628594 OS. While checking the wiring harness diagrams, I noticed the (NQG) assignment on Connector X1 pin 57 [Circuit #1694] and pin 82 [Circuit #1695] relating to transfer case and front axle engagement signals. Which in the tune file relates to several desired torque, torque limits, and speed limit defueling tables.

Thinking this might be a good way to have a secondary fueling table without DSP switch, I tried forcing the tune to run these torque tables by powering pin 82 and grounding the 4LO pin 57 in my bench harness setup. Nothing happened.. Nor did it show any changes under State07 Pids, which reports on transfer case status. I soon learned others doing engine swaps had noticed some conflicts here before.

So I Googled (NQG) and realized that GM assignment is for an floor shift transfer case. With that info in hand, I started searching for a stock tune file I knew was from a floor shift truck. Thanks to Mark B for digging me up a stock (NQG) verified tune file to play with. Which gave me a bit better understanding how this pin assignment works.

There is a another unlisted OS or calibration beside 12628594 that EFIlive hasn't identified, or listed at least. When you pull the tune files, both show same OS#, but couple checksums are different. 1st Hint.. While both versions list as OS 12628594, the "Engine Operation" version under the (NQG) optioned truck reports as 1268777. Different from the tune file I currently had loaded. See below.

So I posted a question about it over on EFIlive forum, in hopes we can find a easy designation difference to identify this different files. Along with hopes of adding ability to make the switch inside the tune files.

https://forum.efilive.com/showthread.php?28888-LMM-OS-12628594-(NQG)-Option

 

[kidturbo]

Got the stock floor shift transfer case file loaded, with VATS disabled, DTC related limits removed, and a truncated the {B1160} Pedal Position to Desired Torque in 4WDLO table so I could identify which mode it's running by pushing RPM above XXXX. Loaded it up on the same ECM, and pins 57 & 82 became active.

To experiment I set up EFIlive Ver 8 scan tool, and monitored PIDs under State07 which contains the ECM 4WD PIDS [AWDSIG] and [AWDLOW],, then added RPM, TP, MAINIQ and few others pids to see what changes.
NOTE: State07 pid in Version 7.5 scan tool are labeled incorrectly, but will still show when status changes.
Then I started feeding the ECM RPM with a crank / cam simulator, TP with Camaro foot pedal attached, and some added POTS in place of the most important sensors, This tricks the ECM into believing it's truly controlling an engine, minus all the wear and tear on hard parts..

In the 2 pics below, you can see how the tune pulled fuel and timing when switched to {B1160} 4WDLO table. First one is in 2WD mode, second 4LO active, with no change in RPM, or other engine parameters.. When I dialed the RPM up past 3200, it starts cutting fuel completely as requested torque is ZERO in that part of 4Lo table. So that works as stated in EFIlive docs. And this table could easily be tuned to hold a set torque at XXXX RPM and throttle position XX when ever the pin 57 is grounded. IE, launch control, or in my case, torque limited when an electronically shifted two speed gear box is in low gear..

Found several other tables linked to these pins. One of interest being {H0108} Vehicle Speed Limit in 4WDLo. Which by factory is set to 39mph. So that opens up some other options like the old valet mode, or in my case, don't allow boat to exceed 40mph while in 1st gear. However speed signal input is not straight forward on these units, which I'll dive into shortly..

 

[kidturbo]

Ok here is where things start getting a little tricky. Depending on which Engine Operating ID your running, the related CANbus messages are slightly different. This is because in a truck with dial knob transfer case control, there is an onboard TCCM ECU to specifically handle shifting duties. One responsible for that nasty [Service 4WD System] message.

In the tunes for TCCM equipped trucks, the ECM is "Told" what position the transfer case by a CANbus message. This particular message ID is sent out by the TCCM on the high speed bus with 8 byes of data. But only two bits of that data actually control which torque tables the ECM looks at. Basically ON/OFF switches for the front axle mode, and another bit for the 4LO signal. One other bit I identified as related to if the TCCM is in a good state or not. But that's pretty much all that the ECM cares about.

Now on trucks without a TCCM, the ""ECM"" sends out this same msg ID over canbus to tell the BCM to switch on the 4X4 light in the dash. However the data contained in these packets is slightly different from the TCCM data version. I highjacked a buddies dash knob truck for a few minutes to capture the canbus traffic and isolated those messages for comparison to my bench rig.

So as THEFERMANATOR mentioned in another topic, if you have the wrong tune loaded in a floor shift truck, the 4X4 light won't illuminate on the dash when you engage the case. Nor will the ECM switch into 4WDlo mode, and thus doesn't follow any of the tables related to low range. Basically ignores the pin 57 and 82 input signals completely best I can tell. Doesn't report any changes on State07 pid either.

Something to keep in mind if your dealing in used ECM's. Just because OS # is same doesn't mean the programing is. Kinda like the two tank volumes, or tire size options. But currently no option under EFIlive to change this pin assignment.

The other way this plays out is if you load a (NQG) tune into a truck equipped with a TCCM. Now you have two ECU's both shouting out transfer case related data on the bus. Neither of them correct. 90% certain the ECM won't respond, but need to load up the first tune again to be certain.

Next I'll dive into some VSS "speedometer" related issues. This one has me stumped since both tunes were written for same TCM. When I send a speed pulse to this (NQG) version on the VSS High Signal [X2-45], the speed is shown correctly monitoring the VSS pid. However the raw HS GMLAN data going to BCM will start out sending a valid speed, then after a short period, goes into an error mode and defaults to 325kmh.

And remember those speed limit tables, they stop working also. But EFIlive keeps displaying the speed being fed to pin 45. Send it some specific canbus packets from the TCM and it remains happy... OR better yet, send it a speed signal message over canbus like it gets from TCM, it ignores the VSS pin and EFIlive PID stops reading... Not sure what they hell they were attempting to do here, but it's screwy for sure.

 

[THEFERMANATOR]

I havent done it with e35b, but e35a WILL work fine with a floor shift tune loaded and a push button transfer case provided the hard wired inputs are connected. I've sent out my duraburb file to quite a few that have push button transfer cases, but connected the hard wired inputs, and they get the 4x4 light on in the cluster and there push button switches. There was a thread over at dp where this was discussed on lbz, lly, and lb7's about using both inputs(hard wired and push button) so you got the 4x4 indicator in the cluster.

And one other thing to watch for, I found in my swap with the lb7, once it switched to the 4low fueling limits, it wouldn't fully go back to 2 wheel drive tables until I turned it off, and then back on. Everything showed it not in 4x4, but it limited fueling until I restarted it. Might want to make sure the e35b doesn't do this to you.