LS1 with PCS TCM-2650 and 6L80 - how to write the transmission tune with no VIN

[Lumina VX]

The guy I have been using for tuning says that HP Tuners will not write a new tune if there is no VIN number for the gearbox or engine. When my Commodore VX had the original LS1 and 4L60e combination, HP Tuners would of course see the car's VIN number through the standard OBD port and therefore it was possible to modify engine/ transmission tunes.

Now that I have a seperate OBD port for the transmission, which comes from the TCM-2650, you can connect HPT to that port to read the tune, but the VIN number has to be present in order for any changes to be written. My tuner said there is a custom lead you can buy (maybe from EFI Connection in the USA?) which will allow HPT to write a file to my transmission. My vehicle's original OBD port under the steering column only shows engine data.

I'm hoping I'm making some sense here and welcome any suggestions! My tuner is being a bit 'distant', shall I say, so I'm a bit lost.

Thank you in advance.

[Alvin]

I'm pretty sure HPTuners doesn't care about TCM vin's. I could be completely wrong but i mismatch them all the time in swaps and have never had a licensing or tuning issue

[Lumina VX]

I'm pretty sure HPTuners doesn't care about TCM vin's. I could be completely wrong but i mismatch them all the time in swaps and have never had a licensing or tuning issue

I think it's because the VIN field is completely blank and a VIN number cannot be manually entered?

[TheMechanic]

You could run a jumper from the CAN high and CAN low wires to the DLC. That would get you what you need.

[Lumina VX]

Please excuse me if I'm misunderstanding your suggestion, but do you mean to connect the CAN high and CAN low wires from my TCM-2650/ 6L80 DLC to the car's original DLC under the steering column, so that we just plug HPT into that DLC and it sees the engine and trans as per normal?

[TheMechanic]

Yes. As long as you have two 120 ohm resistors in the circuit (measure them across high and low with battery disconnected should read approx 60 ohms). You will be able to read them both at the same time. ECM/PCM will already have one of the resistors inside so you only need another module in the circuit or one more plain old 120 ohm resistor between high and low

[Lumina VX]

Thank you very much for confirming. I'll check the resistance, as per your instructions, but I reckon I should already have 2 x 120 ohm resistors in the circuit, as I have two seperate DLC? If so, it's just a case of running the jumper wires, which even I can manage! Then, I can read and write via the main DLC.

[TheMechanic]

Thank you very much for confirming. I'll check the resistance, as per your instructions, but I reckon I should already have 2 x 120 ohm resistors in the circuit, as I have two seperate DLC? If so, it's just a case of running the jumper wires, which even I can manage! Then, I can read and write via the main DLC.

No. Only specific modules will carry the 120 ohm resistor. You can as an example on a late model Suburban have 30 modules. ONLY 2 will have the 120 ohm resistor. The first will be the PCM/ECM. The second can be a TCM or a BCM or even just a plain old 120 ohm resistor in a plastic connector that plugs into the GMLAN line. So simply putting those two together does not mean you get the series resistance of 60 (+ -) 5 ohms resistance. You MAY need to do nothing more that put another 120 ohm resistor between the gm hi and low wires 6 and 14 on your DLC

[Lumina VX]

https://1drv.ms/b/s!AvYJGSX0WE3IkETI...zKGsW?e=4Jx3dz

Thanks again, I appreciate your time with me on this. Hopefully the above link works. On the block diagram, it suggests that the dlc is set up with the 120 ohm resistor, but I'll physically check it with my meter.

[gesmith80]

I have a 2001 Silverado with a 2012 6L80 and TCM 2650 installed. My truck's DCL only has the can low pin (pin number 14) and does not have the can high pin (pin number 6). The TCM-2650 has both can low (OBD2 pin 14) and can high (pin 6). How do I wire so I only connect to the trucks OBD2 port and be able to read and write to the truck tune and the transmission's tune?

Will connecting the can low on the truck DLC to the TCM-2650 DLC (pin 14 to pin 14) with two 120 ohm resistors work for me?

Additional details that may help:
- I can read the transmissions tune file and have it saved to my laptop.
- The trans as specific TECHM and a 2008 6L80 tune file that is suppose to be compatible with the TCM-2650.
- Truck's VIN was added to the transmission but shows up blank in HP Tuners.

Thanks in advance!

[TheMechanic]

The total "system" resistance must be ONLY the 60 ohms of the parallel resistance created by the two 120 ohm resistors. Any more or any less than a measured approx 60 ohms and you will not have com. If need be you could use a DPDT switch that would allow you to use the two different CAN comms while still using a single DLC. Not sure if this answered your question though.