Powers and talks to a GM T87A transmission control module on the bench so you can flash, test and read data off the vehicle.
This is a pre-terminated bench harness for the GM T87A transmission control module, the controller that runs the 10L80 and 10L90 ten-speeds in Silverado, Sierra, Tahoe, Yukon and Escalade, and it also mates with the earlier T87 and the T93. Shops and DIY owners buy it when a replacement TCM has to be programmed before it goes in, when a used module needs to be proven alive before money changes hands, or when a truck has a no-communication code and the question is whether the module or the vehicle wiring is at fault.
The 10L80 shifts clutch to clutch, and the TCM is the part doing the timing. It reads input, output and intermediate speed sensors, commands the linear shift solenoids and the line pressure solenoid, and calculates the ratio it is actually getting against the one it asked for. Transmission Digest points out a detail that catches a lot of installers: every solenoid is flow tested at the factory and its performance data is programmed into the TCM. Replace the TCM, the valve body or a solenoid and the module has to be programmed with the right data, or the transmission will shift badly with no codes at all. A bench harness lets you do that work on a module that is out of the vehicle.
Most 10L80 shift complaints are not the TCM. Solenoid faults, worn valve body bores and clutch wear are far more common; work through 10L80 shift solenoid symptoms and testing and 10L80 valve body symptoms first. A speed sensor that drops out can look like a module failure because the TCM loses its ratio math and defaults; 10L80 speed sensor symptoms shows how to separate them. Suspect the module itself when it will not communicate with a known-good supply and ground on the bench.
The harness is listed for GM T87, T87A and T93 control modules on the 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 10L1000 behind the 6.6L L5P Duramax in 2020-up 2500HD and 3500HD trucks. Before you order, compare the connector on your module with the product photos, because GM used more than one module generation across these years. Send us your year, VIN and the module label if you want it checked. Hard parts for the same transmissions are on the 10L80 parts page.
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Doing this repair right usually means replacing these at the same time. Same transmission, ships together.
GM T87, T87A and T93 transmission control modules, as used with the 8L45, 8L90, 10L80, 10L90 and 10L1000.
No. It powers the module and breaks out the CAN lines. You still need a J2534 pass-thru or scan tool and the software to read or flash it.
A regulated 12 V bench power supply and your interface tool. The harness ships alone.
Yes. The 10L80 TCM stores the flow-test data for each solenoid, so a replacement module must be programmed with the correct calibration and solenoid data.
It can show whether the module powers up and communicates with a clean supply and ground. If it talks on the bench but not in the truck, look at the vehicle wiring and connectors.
No. The connectors come pre-terminated, so it is ready to connect to the module and your power supply.
