4L80e - ECM commanding D4 shift pattern, without a DTC?

[GunmetalGTA]

Car is a 5.3/4L80e. I had it running on someone else's ECM with an HPTuners custom OS. No idea what that tune looked like, but the transmission worked like it should.

I swapped the ECM to a fresh one so I could start working on the tune. I loaded up a 12212156 OS, segment swapped in the 4L80e Express Van transmission calibration and diagnostics, then did the COS3 upgrade. From there I did my best to put together a base tune, and tried to do some driving.

My transmission is commanding D4 shift pattern regardless of my shifter position. I know this can happen when P1810 is set, but I have no codes. (Well, I had P0452 because I don't have the EVAP in place, but that shouldn't change the shift pattern, right?)

Changes to the transmission cal:
WOT shift rpm's raised to 5800
Torque Reduction Tables zero'd out
Abuse Mode disabled

I can command any gear with the scan tool, just not with the shifter.

Any ideas on what could be causing this issue? Are there other conditions where the ECM would command a D4 shift pattern without setting a code?

Thanks in advance.

[joecar]

Try this: go back to the 12212156 + 4L80E seg-swap tune, does trans behave correctly with this...?


Post your 02020003/COS3 tune file here.

[GunmetalGTA]

I would have to source a 1 bar MAP to do that wouldn't I? Maybe I can just idle it to check commanded gear or TFP switch status...

[joecar]

Just try it gently, i.e. drive it round the block, see if it behave properly.


Are you saying that you only have D4, and when you put it in D3 you still get 1-2-3-4...?

[GunmetalGTA]

Exactly. I guess it would only take about 15mph to get a 1>2 shift to figure out if that's the issue. I'll see what I can do and report back.

[GunmetalGTA]

Well I started with the original segment swapped tunes, and GM.TFPSW reads the correct shifter position. It shifts up when it is supposed to hold 1st. When it shifts, GM.GEAR reads 2, GM.TFPSW reads D1... I will revert the transmission parameters back to stock and try again.

[joecar]

Is your harness wired correctly...?

I don't see the pid GM.TFPSW, but I see GM.TFPSWS... I'm not sure if this is the correct pid... try this pid: GM.PRND

[joecar]

Post some logs.

[GunmetalGTA]

When you add GM.PRNDSW, you get GM.TFPSW as well as GM.PNPSW (an in-gear flag that never changes in my case).

Looks like I messed something up with my segment swap. I re-did the segment swap to my original base tune, flashed it in and it worked fine. Next I'll do the COS3 upgrade and see where that gets me.

Segment swaps change more data than just the tables that are available for editing, correct?

[joecar]

Yes, the segment swap changes hidden data/structure/code.

[joecar]

Glad you got the segment swap working, let us know how the COS upgrade turns out.

[GunmetalGTA]

I ended up doing the COS upgrade on the "confirmed good" segment swap, then did the segment swap again into the tune I started with. It works like it should! Now I can get back to actually tuning it! Thanks for your help.

[joecar]

Good job :cheers:

Let us know how your tuning goes.