E38/ T-42 wiring

Hello all
I?m swaping from a 6l80 to a 4l80 in a 2011 5.3 SCSB.
I got a harness (4l60) an t-42 out of a 08-09 truck.
I?m wiring this in an everything matches up correctly except for the X-109 connector.
08-09 truck had as follow
Tan/blk- A8
Tan-A6
D-blue- B8 also goes to pin-18 ecm X1 Along with TCM- pin 11

My truck x-109 as follow.
Tan/blk- A8
Tan-B8
D-blue- unknown

Dark blue is accessory wake up serial data
Tans are can bus wiring.
I believe but was getting late last night that A6 dose not have any wires on the plugs mate. Will verify.

Anyone have any experience with this? What should be done with said wiring to keep things happy.

Thanks!

Hey Sierra09,

Swapping from a 6L80 to a 4L80 in your 2011 5.3 SCSB is a pretty cool project. The harness and T-42 from an '08-'09 truck should mostly plug and play, but as you've found, the X-109 connector can be a bit tricky due to the wiring differences.

For the dark blue wire (accessory wake up serial data) and the tan wires (CAN bus wiring), here’s how you can address them:

1. **Dark Blue (Accessory Wake Up Serial Data):** Since this wire is crucial for waking up certain modules in the vehicle, you need to ensure it's connected to a circuit that's live when the ignition is in the "Accessory" and "Run" positions. If your '11 truck doesn't have a corresponding pin for the dark blue wire in the X-109 connector, you might need to find another source that's ignition-switched. Often, tapping into another accessory power source that fits the criteria can work, just make sure it’s properly fused.

2. **Tan Wires (CAN Bus Wiring):** The CAN bus is essential for communication between different modules in the vehicle. If the '08-'09 harness has the tan wires located differently (A6 and B8) than your truck, it's critical to ensure that these are connected correctly to maintain communication. Since the '08-'09 setup expects these at specific points for its CAN bus network, your '11 truck needs to mirror this setup as closely as possible.

- For the tan/blk at A8, you're good since both harnesses match.
- For the tan wire that goes to B8 in the '08-'09 and A8 in your truck, you’ll want to ensure it matches the '08-'09 configuration to maintain the integrity of the CAN bus network.

3. **No Wire at A6:** If you find that the '11 harness doesn't have a wire at A6 (where the '08-'09 has the tan wire), and it's essential for the CAN bus or another critical function, you may need to run a new wire to the correct pin on the ECM or to another module as required. Make sure to use automotive-grade wire and follow proper wiring practices to avoid issues.

In essence, ensuring the CAN bus wiring is correctly configured is crucial for the vehicle's various modules to communicate effectively. If after doing these checks and modifications you're still unsure or experiencing issues, it might be worth consulting a wiring diagram specific to both models to confirm the correct wiring paths or reaching out to a professional who specializes in automotive electronics.

This swap sounds cool! Keep us posted on your progress, and don't hesitate to ask if you hit another snag.

Thanks for the reply alex14ss Got everything wired up, when I do a gather info on hp tuners both ecm (e38) an TCM T42 appear. I believe I am running into the t42 an e38 not being able to communicate due to the years. 2011 E38 an a 2008 T42..?? Been reading around the forms an it seem like I may need to do a GM SPS for a vin swap on the T42? Anyone know what I’d need to do this? I also don’t have 4wd anymore that could be an issue as well.
Thanks to anyone that chimes in.
Edit: I don’t have the OS Id on me currently but can get them tonight.

ECM & TCM need to both be either 2008-down or 2009-up. Otherwise they will both talk to the DLC but won't talk to each other.

You can write-entire a T42 using HP Tuners, you will have to license the new file though. It might be cheaper to buy a TCM pre-programmed to a VIN you supply the seller.

Alright, is it possible to flash the 2008 T-42 to communicate with the 11 e38 using the GM SPS? I have a connection to the tool. Not sure the steps needed to complete this if it’s possible.
Thanks

Sure, all T42 service numbers interchange.

These are my os ID numbers.. how dose one figure out what vin I would need that would work to flash through the SPS.
E38 OS-12639835
T-42 OS- 24243356
Would i be able to grab a tune off the repository get the vin and use it for the SPS
Any help with this would be great! Thanks.

Finding a VIN for a post-2009 4L80E is easy, any 2009 Express van 6.0L, those are in the repository. However... whether or not an Express van TCM OS will operate all the factory doodads and gizmos (PRNDL/etc.) in a 2011 pickup truck is unknown. However however... since you can SPS the TCM for free as many times as you want, it's no big deal to try it with an Express VIN and see what works and what doesn't. (when you go grab a sample file to harvest a VIN, look at Engine > Fuel and the injector flow rate table's limit - if it is 63lb it is an early one and it won't work for you, only ones with the 127lb limit are the 'late' versions)

I don't think the 80E was ever an option in any regular pickup with any engine by 2011, it only carried over in the vans.

I am using a 2012 E38 from a Sierra, VIN 3GTP1VE02CG125518, OS 12653249
T42, OS 24243356 to run a 4L80/ 5.3 with a 08/09 truck harness in my Camaro.
The harness had a T42 plug and a 4L60 plug. I repinned the 60 plug to the 80 (use the gen 4 pin arrangement---not the gen 3).
I did a stand alone, so you would have to add the wires that you guys talked about above.

So you're saying a '09-up E38 will work with the '09 Express TCM OS?????///forwardslash :shock: :shock: :shock:

Quote:

---

Originally Posted by blindsquirrel

So you're saying a '09-up E38 will work with the '09 Express TCM OS?????///forwardslash :shock: :shock: :shock:

---

No, I am saying it worked for me.

Alright all. So I got the truck back together. Having a no start issue when the e38 is flashed with an auto file. If I select manual flash file in truck will start from the key. Flashed the t-42 with a 2011 t-42 no start. I?m wondering if I have a communication issue? Or a wiring issue? The gear selector shows gears accordingly. When in manual or auto.
Recap of wiring from 2008 truck harness was pulled from.
x-109? Body control plug under fuse box
Tan/blk- A8
Tan-A6
D-blue- B8 also goes to pin-18 ecm X1 Along with TCM- pin 11

My truck x-109? Body control plug under fuse box as follow.
These can wires are the ones I am unsure about as they did not line up with same location.
Tan/blk- A8
Tan-B8
D-blue- I added 12v ignition.

I can pull the files out of both on a read entire I can flash a change the Os ect. Still end up with a no start.

Any thoughts or diagrams be greatly appreciated

Doing same swap on boosted 13 Tahoe, did you get yours done? Any helpful pointers?

I have some notes from my setup. One was that in the T42 connector was to move pin# 45 to pin hole #26.
Also remove white#14 and tan/black #25----this corresponds with the 4L60 plug being changed to 4L80 setup. Looking at the plug, pin E is 12 volts. Remove white S, Remove tan/blk T, The brown wire is U---move the brown wire from U to S. This will run the 80 without the aftermarket wiring harness plugs. You need an ISS plug so in addition to the above wire changes, remove Orange K and Lt blue V from the plug and connect them to your new ISS plug. If you need a terminal release tool for the T42 plug, part# J-38125-21

Quote:

---

Originally Posted by Sierra09

Alright all. So I got the truck back together. Having a no start issue when the e38 is flashed with an auto file. If I select manual flash file in truck will start from the key. Flashed the t-42 with a 2011 t-42 no start. I?m wondering if I have a communication issue? Or a wiring issue? The gear selector shows gears accordingly. When in manual or auto.
Recap of wiring from 2008 truck harness was pulled from.
x-109? Body control plug under fuse box
Tan/blk- A8
Tan-A6
D-blue- B8 also goes to pin-18 ecm X1 Along with TCM- pin 11

My truck x-109? Body control plug under fuse box as follow.
These can wires are the ones I am unsure about as they did not line up with same location.
Tan/blk- A8
Tan-B8
D-blue- I added 12v ignition.

I can pull the files out of both on a read entire I can flash a change the Os ect. Still end up with a no start.

Any thoughts or diagrams be greatly appreciated

---

Not familiar with your wiring issue but I would put the scan tool on it and see if it says you are in anything other than P/N. That could be your no start. Also a cursory check of any current codes. Might help isolate your problem

I did get it going. When I un pinned the 6l80 harness the 4l80 harness pinned to the exact spot as 6l80. I ran 12v to the dark blue accessory wake up wires.
I ended up just using the t-42 for P/n safety, gear indication and the can bus communication in order to keep all the factory functions happy, like BCM A/c air bags etc as I ended up adding a Holley to control everything. Still use the e38 for dash functions, tach (rpm) oil pressure, coolant temp, alternator charging, cooling fans, a/c.
One thing I did come across is the org/blk wire Pin 1 E38 for P/n safety needs to be (-) instead of being wired as a 12v as the P/n switch diagram shows, if you have access to all data or another wiring source it?s good to reference that incase you get caught in a snag.

Quote:

---

Originally Posted by Sierra09

I did get it going. When I un pinned the 6l80 harness the 4l80 harness pinned to the exact spot as 6l80. I ran 12v to the dark blue accessory wake up wires.
I ended up just using the t-42 for P/n safety, gear indication and the can bus communication in order to keep all the factory functions happy, like BCM A/c air bags etc as I ended up adding a Holley to control everything. Still use the e38 for dash functions, tach (rpm) oil pressure, coolant temp, alternator charging, cooling fans, a/c.
One thing I did come across is the org/blk wire Pin 1 E38 for P/n safety needs to be (-) instead of being wired as a 12v as the P/n switch diagram shows, if you have access to all data or another wiring source it?s good to reference that incase you get caught in a snag.

---

were you able to find a t42 os that would work with your 2011 e38 tune?
im just starting down the path of actually integrating the 4l80 into my 2012 (used to be 6l80)
lots of new information and things to learn to make this happen.

Since 2012 was available with either 6L80 or 4L60, wiring diagrams placed side by side for each should be real easy to figure out. Then adapting 60E to 80E is just like on any other trans swap.

Spare uncut harnesses can also be had off ebay for $200-300 to harvest for parts, if you don't want to change out the whole thing. 4-speeds by 2012 had gotten pretty rare, but any Sierra/Silverado 60E harness from '09-up when they changed to the internal mode/range switch should be almost nearly identical expecially if you're just using it for parts.