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just had this happen and the car would not turn off or go into park. Can reset and goes away only to return. Will be dropping fluid and flushing as well as a recalibration and verifying the parking pawl voltage.
I’m aware of the valve body issues but this is the other issue the parking pawl that our cars can have.
Anyone have any of the diagnostic pathways work aside from pawl replacement or dct replacement ?
I wish I could offer some help, but unfortunately cant. Once again, looks like you will be the trailblazer here. Hoping the issue is debris on the magnet. Can your scanner monitor the park position sensor. I have never looked at that with my scanner. Please keep us posted on what you find.
I wish I could offer some help, but unfortunately cant. Once again, looks like you will be the trailblazer here. Hoping the issue is debris on the magnet. Can your scanner monitor the park position sensor. I have never looked at that with my scanner. Please keep us posted on what you find.
The idea that it is caused by debris collecting on the magnet in the hall effect park pawl position sensor comes from a post about "inside information". And it was stated that later transmission have a shield added for that.Have we seen any confirmation that other than that? A bulletin of some sort? Not saying its inaccurate, but it would be interesting to see if that is the cause in this case.
On a side note, I counted, using the Service Manual, at least 8 other hall effect sensors (shift fork positions, ect) that are inside of the transmission exposed to fluid that would be subject to collection of ferrous debris, it that is really what is happening. The transmission pan, as we know, does have magnets, so some ferrous debris was anticipated.
I wish I could offer some help, but unfortunately cant. Once again, looks like you will be the trailblazer here. Hoping the issue is debris on the magnet. Can your scanner monitor the park position sensor. I have never looked at that with my scanner. Please keep us posted on what you find.
I will find out today. I think it can. Thank you . I do believe it’s likely debris .
The idea that it is caused by debris collecting on the magnet in the hall effect park pawl position sensor comes from a post about "inside information". And it was stated that later transmission have a shield added for that.Have we seen any confirmation that other than that? A bulletin of some sort? Not saying its inaccurate, but it would be interesting to see if that is the cause in this case.
On a side note, I counted, using the Service Manual, at least 8 other hall effect sensors (shift fork positions, ect) that are inside of the transmission exposed to fluid that would be subject to collection of ferrous debris, it that is really what is happening. The transmission pan, as we know, does have magnets, so some ferrous debris was anticipated.
I did read there were changes 23 and up that were supposed to to help alleviate some of this. I wonder if that is part of the internal changes? The parking pawl replacement requires two tools I’m worried I won’t get able to obtain and when I have looked to buy one it’s around 1500-2K before the tools. Used DCT is 6-7K so it makes more financial sense to get a used DCT if for anything but to have mine for backup parts.
Thanks, so update I ordered a MDI 2 diagnostic tool and will be able to program the parking pawl as well as a replacement parking pawl itself. Still considering buying a second DCT to just swap in with improved clutches vs fixing this one as this is the second issue I have had thus far with this DCT. So far flush, fluids , etc have not changed my pawl position of 5.8 mm. Even manipulated the external override to see if it would change readings at baseline and it continues to show 5.8 mm (normal is 4.5 mm ). I will see if techlink can find my born position for my car and compare how far it has " moved" and if it can be programmed to a new position that may not require full replacement of the pawl but I am doubtful.
Sorry to hear that. Hopefully, the MDI will help. I assume your scanner could not perform the necessary functions. Which scanner did you try? Is this the same car you successfully swapped valve bodies a few months ago?
I wish the tollerance could be changed. Its such a stupid issue to replace the whole tranaxle.
A software change would sure be easy.
I wonder if a simulator could be inserted between the transmission plug and the harness. It could modify the position to remain in tolerance. It would have to also intecept and interpret the position commands so that it would know what the position is supposed to be. To maintain safety, it could limit the correction it would apply so that if way out of tolerance it would still trigger the necessary logic.
Attached are the schematics showing what I think are connections for the position sensors, and the connections for the position commands. Everything else could be a pass through.
I wonder if a simulator could be inserted between the transmission plug and the harness. It could modify the position to remain in tolerance. It would have to also intecept and interpret the position commands so that it would know what the position is supposed to be. To maintain safety, it could limit the correction it would apply so that if way out of tolerance it would still trigger the necessary logic.
Attached are the schematics showing what I think are connections for the position sensors, and the connections for the position commands. Everything else could be a pass through.
Spoken like an electrical engineer I assume? Awesome thoughts on this.
Sorry to hear that. Hopefully, the MDI will help. I assume your scanner could not perform the necessary functions. Which scanner did you try? Is this the same car you successfully swapped valve bodies a few months ago?
My launch scanner will do the transmission relearn procedure and most of the things needed for say a DCT swap. The issue here is the parking pawl has a specific number on it that has to be programmed to the TCM. (if this number isnt programmed or is somehow not recorded the DCT has to be pulled again) My scanner wont do this. It requires techlink subscription with GM and a scanner capable of emulating the MDI 2 features and functions ( as I understand it). I ordered the MDI 2 so that I will have access and the ability to do this. My launch tool will do 90 percent of things required but the MDI 2 will allow me to try updates to software for all my modules and essentially be able to do anything a dealership can do. There is a thread on here for a cheaper tool that will emulate the features and functions for like 300 but I didnt see it until I purchased this.
I wonder if a simulator could be inserted between the transmission plug and the harness. It could modify the position to remain in tolerance. It would have to also intecept and interpret the position commands so that it would know what the position is supposed to be. To maintain safety, it could limit the correction it would apply so that if way out of tolerance it would still trigger the necessary logic.
Attached are the schematics showing what I think are connections for the position sensors, and the connections for the position commands. Everything else could be a pass through.
Alex peitz reached out to one of his tremec engineer friends and was told no current option for manipulating the stock programming of the TCM to change the ranges at this time (basically told I will need to replace the parking pawl) . I did not speak to this person so this is all third hand so specifics I do not know nor do I have verification of this information but it makes sense to me. So frustrating knowing there really probably isnt a physical issue here but merely a calibration issue due to misreading electromagnetic sensor. I really appreciate your thoughts on this and taking the time to pull up that diagram. With AI and programming now these emulators I would assume are a lot easier to do than in the past. A friend of mine works in cybersecurity and created a OBD2 dongle that automatically deletes the cat codes using an app on your phone in a couple days. Crazy times we live and also crazy that something like this can essentially brick a DCT.
Spoken like an electrical engineer I assume? Awesome thoughts on this.
Well, I figure if they can build a simulator for the muffler valves, this would be possible too. I pulled up the schematic mainly to see if the connections for sensing and control are direct connections (they are apparently) to be distinguished from a serial or digital data connection which would be harder to simulate. Serial data comms are depicted differently in the schematics.
Don't need an degree in engineering to come up with that idea. But to build it.......hmmm.
My launch scanner will do the transmission relearn procedure and most of the things needed for say a DCT swap. The issue here is the parking pawl has a specific number on it that has to be programmed to the TCM. (if this number isnt programmed or is somehow not recorded the DCT has to be pulled again) My scanner wont do this. It requires techlink subscription with GM and a scanner capable of emulating the MDI 2 features and functions ( as I understand it). I ordered the MDI 2 so that I will have access and the ability to do this. My launch tool will do 90 percent of things required but the MDI 2 will allow me to try updates to software for all my modules and essentially be able to do anything a dealership can do. There is a thread on here for a cheaper tool that will emulate the features and functions for like 300 but I didnt see it until I purchased this.
It seems like if there is a specific number the TCM needs then you'd be able to "fake it out" with a different number that would make it happy (although it may not in fact be operating properly).
I'm going to guess that GM doesn't want to change the threshold due to safety concerns. They fear terribly that the car will say it is in park when it is not. So they err the other way.
What she could do is give it a software update so at least its not stuck in ACC hell. ha. Like set parking brake and lets you turn it off, and try again.
Transmission issues p1787 and p1789
