2012 CTS-V 6l90 TCC pressure dump after apply?

[noobers8]

In the valve body.

Is it part of the TCM ?

[TransGo Robert]

It is odd that it happens around the same mph every time though ? light throttle usually. Shifts to 5th tcc locks and I have 6th scheduled to shift at 60mph but it doesn?t until 65 but 60 mph is when the tcc goes from 65psi to 16 psi back up to 58 psi every time? The randomness is what is throwing me off?.. and I do have lock while shift enabled.

By now it has been too long I can't remeber what you are fighting exactly and all that was tried, but what you describe now without having a log to look at to confirm it, sounds like the usual issue with lock-up clutch lining grabbing too much. If this is an aftermarket converter and you have not tried that yet, put a 4 oz bottle of Ford XL-3 frcitions modifier for posi rear end in your transmission and chances are the problem will go away.

[noobers8]

The log is in the start of this post, yes it?s a circle d stage 4 built trans by myself along with a circle d triple disc.

[TransGo Robert]

The log is in the start of this post, yes it?s a circle d stage 4 built trans by myself along with a circle d triple disc.

A whole lot of things can change in 4 months, a log of what it is doing right now would be worth looking at. But from what you described it is doing now and the converter you are using, Either moifying your tune so that it keeps the slip at zero when applied, or adding the additive I mentioned to make it lock less aggressively should take care of the problem.

[noobers8]

here is another log (4 min 3 sec mark)from last night after going back to using the desired pressure table , trying lower apply pressures, widening the apply/release mph spread, disabling adapts, moving desired slip from zero-20-stock and just about every thing else i could think of that would cause a tcc release condition.......

[noobers8]

car is right at the 1000 whp mark ... that modifier wont be an issue on the exedy frictions that i just put in ?

[TransGo Robert]

here is another log (4 min 3 sec mark)from last night after going back to using the desired pressure table , trying lower apply pressures, widening the apply/release mph spread, disabling adapts, moving desired slip from zero-20-stock and just about every thing else i could think of that would cause a tcc release condition.......

Glad I looked at the log, this is not at all what I thought was going on. This is 100% command issue, it is not a problem in the transmission or converter. An input to the computer is glitching causing it to command things wrong. The only singal I can see that looks abnormal is the APP % PID but what you really need there is to record each of the APP sensor output signal in voltage to be able to figure out what is really going on. Every other computer input you logged are stead as steady can be when it is acting up, so it will either be an APP sensors ground issue or it is another input that you did not log. The problem at the 04:06:00.309 minute mark where it drops it out of lock-up completely is obvious as you saw and as I put in a red circle in the first screen shot, but even when it still ends up working ok, the command it bad and keep dropping the TCC pressure for a split second repeatedly between 04:06:23 and 04:06:33 for example. The second screenshot is that part. The clutch ends up remaining applied because the command does not drop for long enough to actually drop the apply pressure significantly, but this is still wrong nonetheless. In both screenshot I have circled the APP % PID signal in light blue, that's either a scanner glitch or the root cause of your problem. At this point, if it was me, I would try to log the less PIDs to get a better sampling rate and log the two actual APP sensor voltage to see if only one is glitching or both. I suspect both (bad ground) or else it should set a correlation code for them but you never know. And of course logging the gear command, TPS, TCC and line pressure command as well as TCC slip.
Cancel.png
Quick drop outs.png

[TransGo Robert]

Oh I forgot to ask, do you still have stock tires (P225/60R18) on this one? If not give me the tire size you have on there, I would like to check something real quick.

[noobers8]

You might be on to something with grounding ?. Last time I pulled the converter, it had welded itself to the crank snout. I chalked it up to crank flex/harmonics . When I log tcc pressure I don?t see the drop outs like you circled but I?m not logging the calced pid either ? Which PID is that ? Or is it a calculation ?

[noobers8]

Oh I forgot to ask, do you still have stock tires (P225/60R18) on this one? If not give me the tire size you have on there, I would like to check something real quick.

I?ll check when I get home but I did the wizard for them. It?s a 28/10.5/19 equivalent

[TransGo Robert]

I?ll check when I get home but I did the wizard for them. It?s a 28/10.5/19 equivalent

Sorry that question was meant for someone else.

[TransGo Robert]

You might be on to something with grounding ?. Last time I pulled the converter, it had welded itself to the crank snout. I chalked it up to crank flex/harmonics . When I log tcc pressure I don?t see the drop outs like you circled but I?m not logging the calced pid either ? Which PID is that ? Or is it a calculation ?

Sorry those are math channel I use on those to know what the real pressure is at the converter clutch and line pressure in the transmsision, I forgot I was using that when I took the screenshots. In my brain being a transmsision guy it is easier to look at this with those values instead of the solenoid pressure output like factory shows. But the drops are there for the regular PIDs as well, just different value. Here's a screenshot with the regular PIDs. The red line graph is the regular TCC pressure PID and the light blue on is for the line pressure solenoid PID. The other two above are math channels I use in my layout.
Regular PIDs.png

[hjtrbo]

The throttle glitch is a scanner oddity. Removing relative throttle position usual makes it go away, or one of the other throttle channels I cant remember exactly. If you want to keep it, look at tps % instead for the log, it doesn't glitch.

[hjtrbo]

Rob would it be ok to get hold of your tcc math?

That tcc pressure drop in the screenshot is real weird. Like its dropping out of 1 mode and into another but its not tracking the set point. Along with Robs checks perhaps look if there is a calibration update on SPS.

[TransGo Robert]

The throttle glitch is a scanner oddity. Removing relative throttle position usual makes it go away, or one of the other throttle channels I cant remember exactly. If you want to keep it, look at tps % instead for the log, it doesn't glitch.

That's what I was afraid off since the noise did go almost completely away when zoom in in closer on the APP % pid. I still would like to see what both APP voltage signal looks like instead of this calculated % PID, surely it must be available in HP Tuner since it is for just about any El Cheapo scanner. I had the TPS selected as well it was the other trace in orange but that's a completely different set of sensors so I would much rather look at the APP sensors voltage outputs.

[TransGo Robert]

Rob would it be ok to get hold of your tcc math?

If the TCC regulator spring is stock, the math is solenoid output pressure multiplied by 1.363636 minus 26.5.

[TransGo Robert]

Like its dropping out of 1 mode and into another but its not tracking the set point.

You lost me there, could you explain to me what you mean by not tracking the set point?

[hjtrbo]

You lost me there, could you explain to me what you mean by not tracking the set point?

Thanks for the math.

My bad, wrong choice of words. If there was some sort of mode change going on, I would have thought it would ramp the pressure as opposed to dropping it like it does. Anyway, very odd behaviour.

[TransGo Robert]

Thanks for the math.

My bad, wrong choice of words. If there was some sort of mode change going on, I would have thought it would ramp the pressure as opposed to dropping it like it does. Anyway, very odd behaviour.

It looks to me like it is just dropping it because it wants to cancel lock-up based on an input that changes but then goes right back up where it was most likely because that input that changes is just glitching except of course for that part when it did cancel lock-up for a while. There is an input somewhere to the computer causing it to change the TCC solenoid command but aside from that APP % of none of the PIDs that were logged so far show any changes when it changes the command.

[noobers8]

well I think Robert hit the nail on the head with the ground comment. for some time now I've had a random Stabil Trak , abs, airbag light that would come and go during 1 key cycle. that paired with the noise on the APP PID made it make sense....i changed intakes about 1.5 years ago and this one came with a shroud that would be installed on the frame rail, to install it you need to remove a ground and use that bolt hole as a mounting point. I removed the paint front both sided of the bracket and applied dielectric grease and reinstalled the bolt through the ground then the bracket and moved on...... this is ultimately the root cause of all my issues. i removed the bracket reinstalled the ground to the frame rail with a stud , then the bracket and went for a test drive ! FIXED

In hind sight i wish i would have logged it with brake position and both APP voltage's but a light bulb went off when you mentioned ground and i went right to it before even test driving again.

https://www.cadillacvnet.com/knowled...t-g110-25.html