Converter or ECM problem?

[jbird007]

Hello, I'm looking for some help, I have a 2008 Duramax Suburban (2008 LMM powertrain) and my converter unlocks as soon as I lift - no matter the condition, even in T/H. When we finished the project the trans would not downshift into 1st until the vehicle was completely stopped for 2-3 seconds. Eric over at Duraburb swapped the A40 with an A50 and the 1st gear issue has been resolved, however, the converter still unlocks. It's not a mechanical problem as I can command the TCC solenoid using the DVT EFI controls and it stays locked. I've checked the transfer case, all sensors, and replaced the brake pedal switch. I have researched this extensively to no avail. Does anyone have any suggestions?

Thanks in advance,
Jason

 

[Harbin_22]

Does this happen at WOT or any throttle position when you let off

 

[GSXRTURBO1]

Sounds like the VSS signal isn't being processed; either the VSS itself or the wiring to/from

 

[Bonestock]

Check logs on turbine slip rpm. If you have more than 600 rpm slip the converter will not lock. You can adjust slip inhibit range from 600 up to 1200 and see if this fixes your problem.

 

[jbird007]

Does this happen at WOT or any throttle position when you let off

Any position.

Sounds like the VSS signal isn't being processed; either the VSS itself or the wiring to/from

I agree, but all data shows VSS signal ok.

Check logs on turbine slip rpm. If you have more than 600 rpm slip the converter will not lock. You can adjust slip inhibit range from 600 up to 1200 and see if this fixes your problem.

Not a problem locking - unlocking is the problem.


LMM locks converter via canbus I think thats where the problem lies. I have a U0117 PTO code but the vehicle doesn't have a PTO.

 

[duratothemax]

LMM locks converter via canbus

uh what are you talking about?

 

[Mike L.]

You still have a PTO switch which could be bad.

 

[jbird007]

uh what are you talking about?

I'm so burned out on this thing I'm talking in circles. What I mean is I have checked 100% of the wiring from the brake switch, ECM, BCM, etc.. Something is commanding it to unlock - I've logged/monitored every PID with EFI. I'm guessing at this point it has to be the data wire since that commands TCC lock in an LMM. Am I wrong? DVT TCC lock works fine - no slip - no unlock. The cruise works, although the slightest decrease in grade (0%TP) makes the converter unlock. I'll try anything...

You still have a PTO switch which could be bad.

Where is the PTO switch location?

Thanks!

 

[Mike L.]

Under center of dash.

 

[jbird007]

Under center of dash.

Well that might be a problem considering this is a suburban? Would it have even had one? Came with 6.0 and 6L80E with tap shift.

 

[duratothemax]

I'm guessing at this point it has to be the data wire since that commands TCC lock in an LMM.

Find me this "data wire that commands lockup" and Ill show you where the button is that makes an LMM's wings pop out and go flying.

 

[jbird007]

Find me this "data wire that commands lockup" and Ill show you where the button is that makes an LMM's wings pop out and go flying.

Thanks for the help! It's always nice to obtain assistance from humble members. I never claimed I knew everything, if I'm wrong about the "data" wire then I'm wrong - it won't be the last time. That's why I came here for help. A trustworthy wiring engineer informed me that that the TCC had a dedicated lockup wire that ran through the under hood fuse center in LBZ and earlier generations, that wire doesn't exist on an LMM and commands to the TCC are sent via can bus. If he was wrong I'm sure you can get him condemned to the gallows in a public place of your choosing..

 

[SmokeShow]

Find me this "data wire that commands lockup" and Ill show you where the button is that makes an LMM's wings pop out and go flying.

Are you going to attempt to help this guy or continue posting smartass comments?

Why are you like that? You have the knowledge to help him, yet instead, you throw jabs. Its nonsense. Either offer some help or hell, offer YOUR HIRED SERVICES if you're not willing to give away the help on a forum (which can be understandable given your investment into learning all of these in's and outs and its your business). If you won't do either of those, why are you even bothering to post? You're being anything but helpful so far.


Just my $0.02 :thumb:

 

[Mike L.]

Seems everyone wants to be handled with kid glove now a days. Everything needs to be politically correct. Too many people get butt hurt too easy.
Ben is Ben. He treats me the same way when we talk and I treat him the same. He means no dis respect. :thumb:

 

[jbird007]

Seems everyone wants to be handled with kid glove now a days. Everything needs to be politically correct. Too many people get butt hurt too easy.
Ben is Ben. He treats me the same way when we talk and I treat him the same. He means no dis respect. :thumb:

I'm a big boy, no disrespect taken. I'm not asking for anything for free - I'll gladly reimburse someone for their time. I have a problem and I'm looking for a solution, no emotion involved.

 

[duratothemax]

Sorry, I didnt mean to come off like that....I apologize...I think I was up late the night before working and Im not the best morning person.

I would put the A40 TCM back in there...are there any codes at all?? Speed sensors all check out ok?

Ben

 

[jbird007]

Sorry, I didnt mean to come off like that....I apologize...I think I was up late the night before working and Im not the best morning person.

I would put the A40 TCM back in there...are there any codes at all?? Speed sensors all check out ok?

Ben

I'll put the A40 back in. With the A40 it doesn't downshift into 1st until I've been stopped for 2+ seconds. Do you have a list of speedo PIDS I can try? The PIDS I tried were all ok. I transplanted a transfer case - is there a speed sensor on the T-case?

 

[Mike L.]

TCM will not command a downshift to 1st till the turbine speed sensor reads 0 . You might want to check that with a scanner.

 

[jbird007]

TCM will not command a downshift to 1st till the turbine speed sensor reads 0 . You might want to check that with a scanner.

Just logged turbine speed and it looked good, no funky readings. Returned to 0 when stopped in gear. I'll switch back to the A40 and check it.

 

[JustAWhiteLMM]

Just a dummy idea, I had one of my old trucks develop that same tc unlocking problem. Turned out to be the brake light switch.. was not an Allison trans, but don't all tc's unlock when you hit the binders?