Torque Converter Lock / Unlock Issues

[pepsi71ocean]

14 minutes ago, Condition1 said:

I put a new alternator on my truck now there is no lock unlock problems even when running the AC. Sorry it took me so long to reply my son turned 16 and I have been working with him to get his license, he took his drivers test today and passed. Also we took a camping trip to the Smokies, truck did an awesome job. Thanks for the info. 

 

did you do a vDrop test on the ground cables? My truck ate 3 alternators in 9 months when the ground started to go bad.

[deej]

On 8/7/2019 at 10:42 AM, Stormin08 said:

i will be the first...you say HAS NOT UNLOCKED ONCE...does this mean that at speed in 4th, when you let off the throttle it is not unlocking ? then locking upon throttle input ? or just simpling saying it isnt hunting ?

 

personally, i think these trucks are very touchy in this area...but it IS supposed to unlock/lock with lack of throttle / then throttle input.

It's not hunting back and forth a thousand times an hour.  It's finally fixed!

[CLorox]

Realizing I am replying to a thread old enough to be a nice aged single malt scotch... I wanted to share my experiences on the off chance it helps the next guy looking through this thread. 

 

I similarly have lit off the parts cannon trying to address this. I applied the w-t mod, cleaned / replaced grounds, re-crimped a ton of cables  (+1 to the cheapo hydraulic Crimpers you can now get for short money on Amazon). I replaced the OSS, found a completely unrelated MAP sensor short, replaced the alternator (Nation's alt), cleaned alternator grounds /  bolts, made new double strapped battery cables.  Nothing helped.  I have learned a lot, including..... that even with the alternator B+ and field wires disconnected, lockup issues STILL happen.  I can't spot any AC leakage with my multimeter with alternator hooked up or unhooked. My triple disc TC was demonstrating no end of issues at both 2-3 and 3-4. It was the wild west of surging and other erratic shifts and surges between 25 and 60mph (seemed kind of happy around 70/75mph).  NO codes. TPS according to Quadzilla data logs looked fine (not dropping out at all). 

 

Here is what worked to me (with thanks to Scott at Massdiesel.com as I was honestly pooh-poohing adding a noise filter on after doing the w-t mod). Even with the alternator cables disconnected I still encounter noise on the APPS causing lock/unlock. I have no idea where it originates and I'll leave it the brilliant minds here to provide a better explanation as to what voodoo happens with the APPS between the ECM and PCM...  Putting that simple little capacitor/noise filter on pin 23 (orange/dark blue) of C1 at the PCM fixed my issue (at least for today) when connected to the cleaned up PCM ground (with alternator wires disconnected and connected). NOTHING else fixed it or improved it. So maybe it comes back (probably).. But that has to indicate something is going on causing noise that is not the alternator (or blower motor/compressor). 

 

Funny side note. While tracing the issue I also found I had a MAPS short in two places. One in the Quadzilla adapter for the 99 trucks, and another in the harness off the ECM. That was causing simultaneous to the lockup issue, an issue with fueling falling flat on its face while building boost (e.g. the ECM/Quadzilla would see 10psi boost and have it drop instantly to 0psi randomly).That caused even more surging. I am running without the MAP hooked to the Quadzilla while awaiting a replacement cable.. The surging that caused while towing a trailer with moderate engine load was contributing to the TC lock/unlock dance.

 

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2024-10-26.. Final (hopefully) edit.   It has been a few months since I wrote/edited this the first time. I'll leave the original text as I thought it might be beneficial to others in the troubleshooting process. My issue was... likely as everyone always says... not resolved in any meaningful way by that filtering capacitor.   My issue stemmed from at least two confounding variables.  Some time after I wrote this, I experienced a much more significant no-start/stall issue when the engine was even slightly warm.  During the no-start I was also seeing ECM issues including a delayed or non-existent wait-to-start light + lift pump circuit failing to stay running.

 

Suspected root causes:

1) I added a bad ground when doing the W-T mod at the step with the m6 bolt at the back of the gear case.  My connection was somehow loose enough to cause the stall issue, but tight enough to not impact performance consistently. Wiggling that ground while the engine was running I found I could stall the motor... I ended up re-terminating this new ground directly to the drivers side battery. This corrected the issue with stalling. This may not have had anything to do with my original Torque Converter issue , but was likely the source of my stall / no-start issue and may have lead to further ECM death. 

 

2) My ECM ultimately had hardware issues.  Using a micropod DRB iii clone/emulator (highly recommend!) I spotted an erratic issue with a high RPM value that was not originating from the CKP sensor. This was causing a few odd behaviors. 1) random cruise control cutouts (cause according to the drbiii was high rpm). I also saw some odd fluctuating voltage readings on the APPS sensor. I suspect one or both of these items were the real cause of the TC lock/unlock.  I sent the ECM to Auto Computer Specialists and they noted several issues (Comms issues to lift pump, lift pump and app circuit shorted, bad wait to start, 5v reference issue, 9.5v reference issue). They replaced several drivers, circuits, a flash chip, and resoldered the cpu and 50 pin connector. 

 

Correcting these two items appears to have fixed all of my electrical gremlin problems entirely.  During troubleshooting, and as a courtesy to my newly repaired ECM, I also took the opportunity to wire in a relay for the lift pump. This had the side benefit of making pump priming a much more pleasant experience (as I can just jump the relay to prime my pump now and do away with the key-start bump dance). 

 

Happy to have the truck running great. I hope I didn't wear my triple disc TC too badly during the lockup hunting issue.

 

 

 

 

 

Edited October 26 by CLorox