Meaning of TCCMODE

[LS1_Dragster]

What does the following commands mean exactly:

TCCMODE PID

AppEn = ?
App = ?

I'm getting real harsh shifts on the 1-2 so I logged TCCMODE and 'AppEn' is on just prior to the 1-2 shift and stays on through the 2-3 shift then goes to 'App' then to 'lock'.

What exactly is being commanded when it's stating 'AppEn'.

'App' obviously is in the apply stage and then goes into the locked stage but I don't know what 'AppEn' is accomplishing.

I'm starting to think the converter is locking during 2nd gear, either by a command or a hardware failure.

[mr.prick]

Status parameter {GM.TCCMODE}
TCC Mode
(Enumerated PID)
Value Caption Description
0 Off TCC Off
1 Rel TCC Releasing
2 App TCC Applying
3 AppEn TCC Apply Enabled
4 Lock TCC Locked
5 Coast TCC Coast
6 Slew TCC Slewed

Right click the PID for more info.
Unfortunately not all PIDs offer "more info"

[LS1_Dragster]

Thanks, but you just stated the obvious! I can and did read that but I'm after the meaning and what exactly is it doing compared to just the App.

Why does it have AppEn from the 1-2 shift, through 2nd past the 2-3 shift then it goes to App then lock, is it actually doing anything to the trans during that stage or is it just there and not doing anything?

Lee

[joecar]

Apply Enable is where the TCC pressure ramped up (via TCC PWM) part way, but not all the way to Locked;

Apply Enable seems to occur between Off and Applying, and sometimes appears to be optional;

The sequence seems to be either of:
Off->Apply Enable->Applying->Locked
Off->Applying->Locked

Applying does not take the TCC all the way to Locked;

Slew or Slewing may be the ramping up/down of TCC pressure over time (but not during Locked);

Coast or Coasting may be where the TCC is unlocked (different than Releasing) and the pressure ramped down part way, but not all the way to Off;

Releasing takes the TCC all the way to Off;


The GM Service Manuals and Hydra-Matic Technician Guides don't refer to those states at all... showpost.php?p=39479&postcount=5

Log TCCMODE, TCCDC, TSTATE00, 03, 09, 10, 12 to get a clearer idea of what the PCM is doing...

For the TCC to be locked, the TCC Enable solenoid has to be on and the TCC PWM solenoid has to be above 95%.

Apply Enable may mean that the TCC Enable solenoid is on and the TCC PWM solenoid is somewhere between 10% and 90%.


Edit: corrections after reviewing my old logs.

[LS1_Dragster]

Mines a little different.

Mine goes AppEn then App then Lock.

If I understand this correctly, the system prepares itself to apply fluid once 2nd gear is enabled (AppEn) now the TCC solenoid is bleeding off this pressure but once the TCC solenoid is energized it no longer bleeds of this pressure (App) then shortly after it's now locked under full pressure.

Is it possible to have the fluid from the AppEn actually start to engage the lockup IF the TCC solenoid is partially failed or stuck in a way so it lets it build pressure to engage the clutch but still not trip a code?

Attached is a screen shot of just normal driving, you can see the VSS jump at the 1-2 shift because it barks the tires, this is even more evident at WOT. Also notice how it pulls timing big time in 2nd gear until it shifts into 3rd. I have no idea where it's getting this timing figure from because I changed the timing in the 'engine protection mode' B5912 to 26 degrees.

Also notice how the TCCSLIP ramps down from dead stop and keeps ramping down even during the 1-2 and 2-3 shifts. This appears to be odd since I have a 2500RPM stall converter, the slip should increase or ramp up after each gear change but less RPM's then the shift before (trans speed is catching up to the engine speed)

Now look at the screen shot from my firebird and watch how the TCCSLIP ramps down from a start but ramps back up after each shift, this to me is exactly how my Yukon should look but with less slip since the firebirds converter is a 3500 stall.

I think I have a defective or clogged TCC solenoid.....

Lee

[LS1_Dragster]

BTW, I only have TSTATE00, 01, 33-37, 39-40, 42 and 45

[joecar]

BTW, I dont see TSTATE09, 10 or 12, I do have TSTATE00 thru 08 also 33-37, 39-40, 42 and 45

You mean in V2 BBL...?

I notified Paul regarding that (those pids either will not display in the scantool since the scantool has no interpretation for TSTATE 33-45).

You would have to log those using the scantool/laptop until they are fixed in BBL.

[LS1_Dragster]

correct, I will have to drag the laptop with the next run then.

[joecar]

Mines a little different.

Mine goes AppEn then App then Lock.
...

Yeah, you're right, I looked at my old logs and edited (blue ink) post #4 accordingly...

[joecar]

Your Firebird log shows the TC allowing the engine rpm to "extend" rather than drop down on take up of shifted gear.

Also note that AppEn means that the TCC may be being partially applied (to control the TCC apply "feel")... see attached diagram and see this description: showpost.php?p=39479&postcount=5