Ok Gang...I've got a for sure way to diagnose torque converter lock up issues where it lock and unlocks at about 45-50 MPH. I had a gent call me yesterday with this problem and he's replace both batteries, alternator and the APPS sensor. Attempted all the different wiring issues (adding ground, tinfoil etc.) nothing worked. Like I told him the truck ran 11 years without all this stuff and doesn't require any wiring change to make it work. What it needs is the damaged part to be replaced. So he's returned the wiring back to stock setup.Now I told him to unhook the alternator fuse and take it for a ride... Guess what... No problems! Even though he replaced the alternator it has a damaged diode in it and it bleeding AC noise into the electrical system.So before doing any wiring mods, tinfoil, adding grounds, adding filter... PLEASE! Bench test your alternator! This is the second time I've suggested this and both time resolved the torque converter lock up issue.

He is still missing the AC noise from the alternator.  

The truck didn't have the issue when it left the factory, something on the truck is broken....fix the broken part.

Ive been dealing with this issue for a long time, VDC 14.1 VAC .001-.002 took the alt yesterday to get it rebuilt with new diodes and brush. Put the alt in today took it for a drive it did it once really quick or so I think it did.  I was also getting a code when I did the key cycle of P0720 and P0743 why those came up I have no clue. Gonna go out now for a long drive and shut the truck down a few times along the drive to see if I can get it to act up again, if it does the truck is for sale Ive put more in the truck than what I paid and Im bout done.

Those codes are both point to a sensor issue in the trans.

 

Have you replaced the VSS on the trans?  ( its so stupid cheap you should anyways) and the lockup solenoid. 

 

 

brand new ATS stage 4 and I was dealing with this issue prior to the tranny swap. I had cleaned all the grounds and I mean all the grounds and it quit for about 6 months. speed sensor has been replaced twice. Only thing I could do next is replace all the pigtails to the tranny connections.

New Tranny has less than 1000 miles on it.

did they replace the solenoids?  

 

Tranny is a complete brand new build, they even sent me a brand new valve body and sensors to replace and they sent me their "band aid" fix like the BD fix. 

Did the band aid do anything?

 

How are you battery cables looking?  You said after you cleaned EVERY ground on the truck the issue went away for a bit?  That really sticks out for me.

17 minutes ago, Me78569 said:

Did the band aid do anything?

 

How are you battery cables looking?  You said after you cleaned EVERY ground on the truck the issue went away for a bit?  That really sticks out for me.

bandaid has done nothing. I took it for a ten mile or so test drive after I put the alt back on and it hiccuped really quick I just check the key codes and the P0720 has popped up again. I know it can't be the sensor Ive been thru 3 of them and they all still work brand new out of the box. Pigtails might be my next choice or new battery cables all around but again just more money thrown into this thing. 

I would start ohming out wires from the trans to the PCM.  

 

It should be pretty easy to tell if you need new cables.  How do they look?  still tight? any corrosion? 

2 minutes ago, Me78569 said:

I would start ohming out wires from the trans to the PCM.  

 

It should be pretty easy to tell if you need new cables.  How do they look?  still tight? any corrosion? 

they looked good when I did the swap and since then I pulled it completely out and checked each wire for exposure and connections with electrical grease. I mean it could be a pin but I looked at all the connections and you can see plain as day the pins are intact in all the connections, but as many times Ive unhooked and reconnected it could be possible to have a loose pin. Im at a loss now and completely bored now.

the only GOOD thing about the truck is, no truck payment.

I understand the frustration.  

 

I have had a clunk in the front of my truck for as long as I have owned it.  I have replaced every piece of suspension under the truck and it is still there.  I can't figure it out....so I ignore it.

 

How do your battery cables look?  

17 minutes ago, Me78569 said:

I understand the frustration.  

 

I have had a clunk in the front of my truck for as long as I have owned it.  I have replaced every piece of suspension under the truck and it is still there.  I can't figure it out....so I ignore it.

 

How do your battery cables look?  

they "look" perfect always clean and always lubed up. Im about to do a continuity on all the neg cables now 

well good luck man.  

Just out of curiosity, what's the history of the truck? Have you owned since new? Has the previous owner done anything hard or anything to put extra strain? It seems to weird to me that some trucks never have issues and others have these 'ghost' problems. Just trying to come up with some sort of correlation.

Why not put a manual torque convertor lock-up switch until the problem can be resolved, if ever. I'm not having any problem with my trans now but I do have a lock-up switch, I use when towing, with automatic disengagement when the brake peddle is depressed.  It works great 

Brake light switch possibly on the outs?  

 

Trying to think of things that can cause unlocking.

Im the second owner bought it from a 73 yr old man and had 90,000 miles on it well taken care of and he documented everything. I Bought it in 2007 ish and it started doing this about 1-2 yrs later. what you see in my sig is the only thing I've done to. The ATS came with a lockup controller. Recently replaced the VP with a blue chip. 

24 minutes ago, Me78569 said:

Brake light switch possibly on the outs?  

 

Trying to think of things that can cause unlocking.

haven't really checked that but I just got back from a long drive and its doing it more than ever now with P0720 code output speed sensor. replaced it 3 times already so Im gonna assume the plug end is bad somewhere.

Edited February 17, 20169 yr by Carl Steven Clendenning

yea thats a safe bet.

 

maybe ground the wire in question on one end and use a multimeter to try and find a break.

damn, sorry to hear that you're dealing with all this. Always bums me out to hear people having hard to find issues on these trucks

7 minutes ago, notlimah said:

damn, sorry to hear that you're dealing with all this. Always bums me out to hear people having hard to find issues on these trucks

Thanks, I'm giving it one more shot to figure this out, if not I'm selling it.