2009 4L60e with 2007 T42 TCU issues

[513Motorsports]

I am running an E38 from a 2008 Yukon OS1250216 and a T42 computer and harness from what I believe to be a 2007 Silverado OS24239927. I had an older 4L60e in it that lost 3rd and 4th gear (possibly from wrong tune settings?). I just picked up another 4L60e from a 2009 Silverado and installed it.

The problem is that the trans is going into 2nd gear only. I believe it has communications, as the scanner tool showed trans temp and gear selector position. I can't even get it to take a command for a different gear or lock the TCC with Scanner. Is it possible that I need a T42 from a newer vehicle with this trans? If so would I have to add the additional wires and repin my TCU connection?

Thanks,
Joe

[513Motorsports]

I'm thinking I need 2009 T42 OS 24243356. Can I change the OS of my T42 or do I have to buy a new one? I see that in 2009 they made some changes to the 4L60 by removing the 3-2 solenoid and making the PNSS internal to the trans.

[513Motorsports]

Here is my current tune.

[ScarabEpic22]

In 09, GM changed the 4L60/65/70E transmission. No more 3-2 solenoid, different PRNDL switch, and a few small things. Basically, you need to use the exact settings from an 09+ 4L60/65/70E tune to run that transmission. First, make sure the TCM has the matching TCM OS for the ECM OS. I.E. make sure the TCM OS works with your 08 Yukon ECM OS. From there, you need to copy all the differences from an 09+ T42 4L60/65/70E tune to your file. There are also some wiring changes, you'll need to track those down as well.

Check out this thread for more info: https://www.hptuners.com/forum/showt...d-17-pin-4L60E

[513Motorsports]

Thanks for the reply. The TCU that I am running is the same one that I was running before with the older trans that worked. I checked the pin out trans to T42. I still have the external PNSS hooked up and working. This seems that it should do the same thing as the internal one without having to repin the trans connector. It looks like Pin N is different, but I should be able to drop that out of the T42 plug and ground it since it looks to be the ground source for the Park/Neutral signal pass back for the internal PNSS. I loaded all settings in from a A4 2009 Silverado and cross checked them against an A4 2010 Silverado. It still does the same thing. I read the link you posted. Here is what I found interesting. There was a place where it mentioned removing the 3-2 solenoid in the program: Trans -> Auto Shift Properties -> General -> General -> Downshift 3-2 Solenoid: Disable. I overlooked that last night. What is interesting is that is still enabled on the 2009 and 2010 tunes that I downloaded. I'll try to disable that and see if it helps. I also have a TCU that is from a 2009-2013 Silverado coming that is my plan B. Thanks for the input. I'll keep updating as I get more info.

[513Motorsports]

I dropped pin 42 out of the TCU harness plug, plugged in the new TCU (OS24243356), disabled the Downshift 3-2 solenoid and tested it on the lift. Everything appears to be working. I have a mechanical pressure gauge installed as well to try to figure out what may have caused the last trans failure. Pressures look good and respond to throttle position. Gear position indicators work and I can command the trans with HPTuners Scanner Tool. Now that all works, I may try a couple of other combinations to see what else works so I can report back for others that may have a similar issue.

Erik,
Thanks again for taking the time to reply.

Joe

[ScarabEpic22]

Glad you got it working Joe!