View Full Version : A40 in "Engine in Default Mode Shift Pattern"

November 14th, 2017, 06:15 AM
We have a 2WD 2006 LBZ that we are building into a race truck and are having issues with the transmission shifting when it wants to regardless of how I tune it. It will not do a 2nd gear launch and will shift way too early on other gears. I have setup the tables I can see in EFI Live to the same value accross the board - all modes and all thottle positions, and the WOT tables.
1-2: 0mph, 0RPM
2-3: 63mph, 4800RPM
3-4: 86mph, 4800RPM
4-5: 115mph, 4800RPM
5-6: 318mph, 8000RPM

Yet the truck will shift through the gears like the TCM is not even tuned and be in 6th by 60mph. So I dug deeper and started looking at the PID TSTATE17, which shows you what shift mode you are in; and TSTATE61 which shows you if 4Lo input is active or not. Grounding pin 42 will not show that 4Lo is active like it should. And the only mode that will show yes under TSTATE17 is TSTATE17-SPLIMP "Engine in Default Mode Shift Pattern". On another 2WD LBZ you can toggle between TSTATE17-SPNORM and TSTATE-SPTH saying yes by turning TH on and off. On this truck I tried to remove the pin 54 for the trans fluid temp input and it showed -40* and went to TSTATE17-SPCOLD showing yes, which we also can't see or tune through EFI Live; but I got excited that I may be able to force it into a shift mode that we can tune, so I grounded pin 54 and it showed 320*, but went back to TSTATE-SPLIMP, instead of TSTATE-SPHOT "Hot Mode Pattern". It is not in a normal "limp mode" as far as getting stuck in a certain gear, it shifts perfect and smooth, just not at the set points in the tables that are tunable with EFI Live. There are no TCM codes, and no ECM codes that are turning on the CEL. There are background codes that are disabled like P0103 (MAF is deleted), P0405, etc. - but no active codes. I have made sure that the ECM file the tuning is based on is the correct stock file for the truck, with the correct Speedo and System segments; I have tried 2 different TCMs with 2 different operating systems.

So I need to figure out what can cause it to go into "Engine in Default Mode Shift Pattern" so that I can get it to stop doing so; force it out of that mode and into a mode that can be tuned (Normal, Tow/Haul, 4Lo, or Hot), or get access to the tables for either that mode or cold mode. Out of the 7 shift modes we can program 4 and of course the only 2 I can get this truck to go into are ones we can't tune.

November 14th, 2017, 10:47 AM
If I turn the key back to accessory position, then back to run it will show normal mode for a split second, if I hit T/H during that time it will switch to showing TH mode, but then it goes back to default shift mode.

Also I get a U0100 code from the TCM. Some diagnostics on that code are to check resistance between pin 6 and pin 14 in the OBD II for 60 ohms resistance, which I have with the key off, and I can communicate with the ECM and TCM through OBD II. Also the TCM is showing throttle and torque values from the ECM - so they are communicating with each other.

November 14th, 2017, 05:56 PM
I hate when I find old threads that were never answered when I am looking for the same answer, so won't leave you hanging:

I found the issue tonight doing some testing on another truck. Truck showed normal mode, running or KOEO (Key on engine off), and could be toggled to TH mode. I went out and unplugged the MAF sensor (which is deleted on the truck that was having an issue), and even without a check engine light it put it right into the TSTATE17-SPLIMP "Engine in Default Mode Shift Pattern" and TH button went unresponsive (light works, but nothing on TCM changes). Plug it back in and it goes straight back to normal or TH mode. I'll be wiring a MAF sensor up in the morning and hopefully at the track tomorrow night taking the record for the fastest stock bottom end back.

November 14th, 2017, 11:17 PM
Glad you found the problem and thanks for not leaving the thread un answered. I too hate that.