6L90 won’t shift into 4th after rebuild

The TCM is locking you/scan tool out of 4th, 5th, & 6th because there is no output speed signal. (The TCM will not let you take off from a stop in a higher gear than 3rd)

4th command would look like this (with the scan data provided)....
PC2....No
PC3....Yes 4-5-6 Clutch
PC4....No
PC5....Yes 1-2-3-4 Clutch

As you can see in the video, The TCM is still commanding 3rd even though you commanded 4th, 5th, & 6th.

3rd.....
PC2...Yes 3-5-R Clutch
PC3...No
PC4...No
PC5...Yes 1-2-3-4 Clutch

Pull the pan & connect the speed sensor harness.
 
clinebarger said:
The TCM is locking you/scan tool out of 4th, 5th, & 6th because there is no output speed signal. (The TCM will not let you take off from a stop in a higher gear than 3rd)

4th command would look like this (with the scan data provided)....
PC2....No
PC3....Yes 4-5-6 Clutch
PC4....No
PC5....Yes 1-2-3-4 Clutch

As you can see in the video, The TCM is still commanding 3rd even though you commanded 4th, 5th, & 6th.

3rd.....
PC2...Yes 3-5-R Clutch
PC3...No
PC4...No
PC5...Yes 1-2-3-4 Clutch

Pull the pan & connect the speed sensor harness.
Click to expand...
Today’s title - “Should I have bought 2 of everything?”

 
clinebarger said:
DTC's?
Click to expand...
No codes. Quick breakdown, still just rolling on jackstands:

Last night -initially had Reverse and could shift through 1,2,3 but nothing would change when I commanded 4. Once the fluid heated up (I got around 90) I lost Reverse and it seemed stuck in one gear (felt like 3rd).

Today - again had Reverse and 1-3 when cold. Still no solenoid or physical change when commanded into 4th. (I misspoke in the video, not ALL gears). When the fluid got to around 70 Reverse began having the wheels spin forwards. Finally when it go up past 80 degrees Reverse was gone entirely and again it felt stuck in one gear, again seemed like third.

Is this a TECHM issue or a Valve Body issue? Did I screw something up when doing the Sonnax Zip Kit? Or could the initial failure have wrecked the VB and I need a new one?

 
So I still don’t know what’s going on, but I was lookin at the the 6L80 ATSG solenoid activation chart (the bottom one in the picture) as well as the one in the Sonnax Zip Kit instructions (top in the picture) and going off my assumption that it feels stuck in 3rd when warmed up, I noticed a disconnect between the two. The Sonnax chart shows Shift Solenoid 2, CPC #5, and CPC #2 all commanded “On” in 3rd. However, the ATSG chart shows Shift Solenoid 2, CPC #5, and CPC #3 (what my scan tool showed) all commanded on in 3rd.

Am I reading something wrong or are these mistakes?


IMG_7624.webp
 
Read the foot notes, ATSG has the Normally High PC Solenoids operating inverse of the Normally Low PC Solenoids which is technically correct but causes confusion.
 
You're 100% sure the TEHCM got programmed?, Sonnax TEHCM's come with a calibration that is for cleaning & testing only.
If you happened to get one with a compatible Operating System.....It will act really wacky & not set DTC's.
 
clinebarger said:
You're 100% sure the TEHCM got programmed?, Sonnax TEHCM's come with a calibration that is for cleaning & testing only.
If you happened to get one with a compatible Operating System.....It will act really wacky & not set DTC's.
Click to expand...
I’m really not sure how I could have messed it up. I used a GM MDI and bought access to SPS through Techline Connect. Then I went in and selected TCM and hit program, and it showed that it took the calibration number.

Also, even if it didn’t I still couldn’t shift up into 4th with my old TECHM. Unless that was an internal problem that I have since corrected.

I can film the programming process if it would help.
 
Nate-B said:
I’m really not sure how I could have messed it up. I used a GM MDI and bought access to SPS through Techline Connect. Then I went in and selected TCM and hit program, and it showed that it took the calibration number.

Also, even if it didn’t I still couldn’t shift up into 4th with my old TECHM. Unless that was an internal problem that I have since corrected.

I can film the programming process if it would help.
Click to expand...
I guess I can always try throwing the old TECHM back in and see what happens or if anything changes symptom wise.
 
Nate-B said:
I’m really not sure how I could have messed it up. I used a GM MDI and bought access to SPS through Techline Connect. Then I went in and selected TCM and hit program, and it showed that it took the calibration number.

Also, even if it didn’t I still couldn’t shift up into 4th with my old TECHM. Unless that was an internal problem that I have since corrected.

I can film the programming process if it would help.
Click to expand...

Sounds good!

The reason I questioned the programming is it appeared to take off in 4th (Or 3rd depending on how the scan tool is displaying PCS states) in the last video.

I use HP-Tuners for in-depth diagnostics on these & I find using "Clutch Pressure Command (PSI)" to be a more fool proof way of discerning PCS states.
The Solenoids are fed with AFL pressure, Max AFL pressure is @ 100psi.


PCS #5 Clutch Pressure Command of 100psi means the 1-2-3-4 Clutch is commanded on for example.

In the first test drive video you posted, On stands, No ISS/VSS?.....You had 1st gear.
SS1 ON
SS2 ON

PCS2 OFF
PCS3 ON.......This is Low/Reverse Clutch Apply when SS1 is ON, NOT 4-5-6 Clutch Apply!
PCS4 OFF
PCS5 ON.......1-2-3-4 Clutch
zrGM16R.png

3LeyXdS.png
 
In your last video....

SS1 is OFF & SS2 in ON, Meaning PCS#3 is applying the 4-5-6 Clutch.

PCS2 OFF
PCS3 ON
PCS4 OFF
PCS5 ON

Looks like it stayed in 4th gear the whole time.

Uu1kbPs.png
 
At face value....The unit is doing what it's commanded to do, But why would it be locked in 4th with no DTC's?

I'll try to get a good data capture with my Autel Elite tomorrow on my L96/6L90 swapped Silverado for some reference as your OTOFIX appears to be Autel based.
 
As you can see, Taking off from a stop.....The L/R Clutch is applied until about 3-4 MPH...Then PCS3 & SS1 is commanded OFF.
This is done to provide extra support to the L/R Sprag.
yKLOjt8.png




This is 1st after the L/R Clutch is disengaged.....
xFHDFJ2.png




2nd Gear....
wAewGAM.png




3rd Gear....
U694Xkl.png




4th Gear....
Jh25nUy.png
 
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