Powers and talks to a GM T87A transmission control module on the bench so you can flash, test and read data off the vehicle.
The T87A is the transmission control module General Motors runs on its 8-speed and 10-speed rear-drive automatics, and it is a module you often have to deal with on the bench rather than in the truck. This harness terminates the TCM's vehicle connectors and breaks them out into a standalone loom so you can put power, ground and a CAN pair on the module by itself. It also fits the earlier T87 and the T93 control modules used across the same family.
On the bench you feed the harness from a regulated 12-volt supply, land the CAN high and CAN low leads on a J2534 pass-thru or a scan tool, and the module wakes up and reports. That is what you need to flash a replacement TCM to the VIN and calibration before it ever goes in the vehicle, to prove a used module actually boots and communicates before you buy it or install it, and to sort out whether a no-communication complaint is the module itself or the truck's harness and connectors. Swap builders use the same setup to bring up a 10L80 or 10L90 standalone outside of a donor chassis.
Fitment covers the GM 8L45 and 8L90 (Colorado, Canyon, Camaro, CTS, ATS, Silverado 1500, Sierra 1500, Corvette, Escalade), the 10L80 and 10L90 (Silverado 1500, Sierra 1500, Tahoe, Yukon, Escalade, Camaro ZL1), and the Allison-badged 10L1000 behind the 6.6L L5P Duramax in 2020-up 2500HD and 3500HD trucks. The connectors are pre-terminated, so there is no pinning or splicing to do before you can use it.
What ships is the harness only. You supply the bench power supply and the J2534 interface or scan tool. Note that a bench harness lets you talk to the module; the actual programming still depends on your tool and your subscription or software.
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