Decided against the $800 TCM 2650 interface to run the 47K mile 6L90E I recently acquired. Instead for a small amount more $, I am going with an E67 PCM for a 2009 Trailblazer SS and a 58x conversion with drive by wire and coil near plug ignition. Seems like a better option to update the engine management and get a new engine harness at the same time.
I found probably the last new GM 2016 L96 6.0L Express van engine harness for $300. Scored one of the last new GM E67s for the Trailblazer as well for about $285. Finally I was able to find the OEM service manuals for my 97 for $48 shipped still sealed in plastic. I also downloaded a ~950 page PDF file from the GM Upfitter site for the 2016 van. I also found the 2009 Trailblazer SS engine wiring diagrams for $6.00 from an online site specializing in harness diagrams. Going to repin the 2016 E78 van harness to use the E67 and rewire my vans current engine harness to accept the trimmed down 2016 harness.
I am going to build a standalone transmission harness for now to run the 4L85E with a T42 TCM for a ~2010 Express van. Get my van wired, running and tuned with the E67 swap. Then when I finish acquiring parts for the 6L90E swap, it will be a simple wiring operation to swap the 6L90E in place of the 4L85E. The T42 TCM runs nearly completely on its own via 2 CAN bus wires to the PCM with the bulk of its connections being to the 4L85E itself. The 6L90E uses a T43 mounted directly on the valve body inside the unit and has an even more simplified wiring setup. I am leaving the T43 connections in the 2016 harness and will merely unpin the 2 CAN bus wires. To put the 6L90E in action, will have to move 2 wires back to the PCM pins after removing the T42 setup.
I thought I was going to have to buy new Molex connector bodies for the E67, but the E78 ones are the exact same. Just have to repin the E78 harness for the E67 PCM and trim out the 2016s body harness and fusebox wiring to marry to my 97s body harness wiring. I will probably repurpose one of the un-used body harness multiple pin connectors and get the matching connector and pins to it to connect my existing harness to the new engine harnsss to allow for easy engine harness removal in the future should future repairs be required.
To make my Gen1 SBC talk GenIV LS is fairly simple. The 58x reluctor wheel is an off the shelf EFI Connection part. The cam sensor setup is an off the shelf GMT900/late model Express 4.3L V6 part consisting of a distributor drive and cam sensor. The flat response knock sensor adapters are also an off the shelf marine part as well as a EFI Connection part. They are either machined studs or bushings that thread into the block drains on the SBC and a pair of $20 LS2 style flat response knock sensor bolts on to them.
The drive by wire accelerator pedal from a later model van bolts right to my firewall. The 4 bolt 90mm LS2 style throttle body bolts to my 3 bolt intake with a normal LS 4 bolt to 3 bolt adapter plate. The LS coils can be mounted remotely and hooked to normal plug wires to run the SBC. I happen to already have a DBW pedal, DBW 4-bolt 90mm throttle body and several sets of LS coils.
It looks like the 6L90E will bolt in using a 98-02 4L60E crossmember for the later 4L60E, a newer 6L90E van driveshaft, trans cooler lines, shift cable, filler/dipstick tube and dipstick will also bolt pretty much right up. I intend to get the newer shifter with tap up, tap down, and tow haul integrated as well as a CAN bus module that integrates the tap shift/tow-haul and reverse light output into a single module. My cruise control switches and VSS outputs for the cluster and ABS are able to be directly wired to the 2009 TBSS computer as well, preserving their functions.
Finally the TBSS computer will also still run my PWM controlled EV fan clutch because it is from a Trailblazer, simple enough. I will use the newer van 02 sensors that match the connectors in the harness. They are under $30 ea and my old 02s could stand to be replaced anyway.
I have found an interesting thing I did not know as well. With the PCM and TCM I plan to run paired together in the CAN databus, HP Tuners will read the E67/T42 or E67/T43 pair for the base tune and allow me to tune both as a matched pair.