Turboalky

http://blog.obdii365.com/2024/01/22/launch-x431-chevrolet-corvette-hydraulic-system-flush/

Interesting read
Launch x431CRP919E

Andybump

https://www.corvetteforum.com/forums...y&p=1607936182

There are two things I notice about it. First, the article does not say anything about only being able to run it on later models. There have been statements on the forum that software necessary for the HSF resides in the TCM in later models, but not earlier ones. And supposedly the GM tool can run it on the earlier models. Aftermarket tools supposedly not. Edit- oop, as pointed out in the next post - it does mention that.

The second one is how it mentions the "7 individual procedures" and how they were on the tool but were removed and "replaced by" the HSF procedure. It is an assumption (one I have also speculated about) the HSF performs those 7 procedures. What is interesting to me about that is that each of those seven procedures were a "transmission service cleaning procedure" and each addressed one or more specific valves in the system. And in the early service manual they are not called out together - if a particular DTC is set - and after some diagnostics - it call on a specific cleaning procedure (I don't have a later manual). So it would appear that the cleaning procedures do things to free up debris from specific valves. To me, if the HSF is actually performing those cleaning procedures in a specific sequence, this seems a lot more involved than what Josh Holder said when he seemed to say all the HSF does is just cycle "more" fluid through the transmission. Here is his statement, and I have attached the list of the 7 individual procedures. Hmmm.

"The hydraulic system flush does kind’a the way its described. It forces transmission fluid through the fine filter that you replace. So, at a dealership they can hook up the dealer service tool to the and run a routine that will tell the trans control module to do this fluid filter flush. And because the car is already hoisted on the rack, the technician’s already got the panels off, there’s some other work he’s doing, this kinda happens in parallel in the background. So we’re doing it at a dealer visit because we can. And we can take the last bit whatever contamination might be in the oil and get it into the filter before the technician replaces it. Do it yourselfers have become nervous that hey now I can’t do it myself, I don’t have a service tool, I can’t force this routine. You don’t have to do the routine. Like I said we do it because we can, but the fine filtering routine happens during normal driving anyway. In fact, when you’re driving steady state like say down the highway, we run a routine in the transmission that will force more of that fluid through the fine filter. So normal driving is doing this. If you are a do-it-yourselfer, you don’t want anyone else touching your car, you can change the trans filter without running this routine."

Turboalky

It does state lower in the write up that only the '23 and '24 have the code written in the software.
I have a '23 and want to do my own DCT filter change early when I do my first oil change.
Thanks for all the great info

Andybump

I missed that. I'll fix my post. Thanks!

jthornton

So I'm wondering if this is only in the 2023's with the improved DCT that doesn't need a track fill?


JT

Turboalky

Not positive but from what l have read all '23's and up have the software written in the TCU.
Case change was only late 23 vin #'s

Andybump

Interestingly, the 7 individual cleaning procedures have been in even the very early 2020 Service Manuals (and may have been removed when the HSF was added - I don't have a later version). If I follow correctly, the 7 individual procedures could be executed on the 2020-2022 vehicles with an aftermarket tool. Is that correct?

I think it is still a mystery - and assumption - that the HSF just executed the 7 cleaning procedures in a certain sequence - perhaps the order is not even important. But there is a bulletin that asks the tech to perform one or more of the cleaning procedures, followed by the HSF. Here is some history on that.

From what I have found, the HSF may have first appeared in a bulletin 21-NA-033. The first version of this was released in Feb 12, 2021. I cannot find the original Feb 2021 version, but it is discussed in a TechLink article dated Mid February 2021. That version discusses "Multiple Transmission DTCs Set" and the procedure says to execute one or more of the 7 transmission cleaning services that correspond with the DTCs set. Not all cleaning procedures listed need to be performed, it says. If that fails, it says replace one of the valve bodies. The Hydraulic System Flush does NOT appear in that discussion in Feb 2021. Here is the link to that one:

https://gm-techlink.com/wp-content/u...ruary_2021.pdf

The next version of this bulletin was released in June of 2021 (I can tell this from the summary of the release dates at the end of the bulletin dated Dec 15 2021). It says that version "Added a Note at beginning of Service Procedure and new GDS information to steps 8 and 9." Steps 8 and 9 in the Dec version now include the Hydraulic System Flush, to be performed AFTER completion of on or more of the individual 7 cleaning procedures. To be clear, it has the tech perform on or more the cleaning procedures first, followed by the HSF. There is NO step between them to first check to see if the problem is fixed. That check now comes after the HSF.

I can't find the June version, but here is a link to the December 2021 version that has the HSF added.

https://static.nhtsa.gov/odi/tsbs/20...12566-9999.pdf

From what I can tell the last version of the bulletin was issued in Nov 2022. This version deleted the entire procedure. I think, but cannot prove, that this is because procedures were added to or updated in the Service Manual(s) making the bulletin obsolete. I think this because this last version now directs the tech directly to the service manual if any of the p-codes are set. Here is the link to that "last" version:

https://static.nhtsa.gov/odi/tsbs/20...27053-0001.pdf

This is an interesting example of how service procedures can evolve and result in confusion for techs working on your car.