Rebuilds the TEHCM pressure switches on GM 6L80 and 6L90 valve bodies with new laminate discs, seals and the piston and installer tools.
A GM six-speed that throws pressure switch codes such as P0842, P0847, P0872 or P0877, shifts erratically or drops into limp mode is often suffering from tired switches inside the TEHCM rather than a dead computer. This kit rebuilds those switches on the 6L45, 6L50, 6L80, 6L90 and first-generation 6T70 and 6T75, so a Silverado, Sierra, Tahoe, Yukon, Escalade, Camaro or Corvette owner can repair the module they already have instead of buying and programming a new one. It includes enough laminate discs and seals for one TEHCM, plus the piston, seal plunger, seal installer and laminate installation tool, with printed instructions. It serves as a replacement for the 124740-TL30 tool kit.
The TEHCM is the transmission electro-hydraulic control module bolted to the valve body: the computer, solenoids and a row of fluid pressure switches in one unit. Each switch is hydraulically tied to a clutch regulator valve. Sonnax explains that the switches tell the computer which gear is selected and give it clutch timing feedback, which it uses to track clutch wear and adapt shift timing. The switches are normally closed. When oil pressure reaches one, it pushes a thin laminate film down against a piston and disc and separates the contacts. If the film waffles, delaminates or the seal leaks, debris gets into the contact area and the switch reports the wrong state.
Read the codes and watch the pressure switch states on a scan tool that shows them live. A switch that never changes state, or changes in the wrong gear, points at the switch. Check the TEHCM connector and fluid level first, and rule out low line pressure, because a switch that never sees pressure will also set a code. Our 6L80 Escalade shift problems guide explains why so many trucks end up with a TEHCM they did not need, and the 6L80 Camaro shift problems guide covers the line pressure test and adapt reset to run before any parts go in.
Listed for the GM 6L45, 6L50, 6L80 and 6L90, and the Gen 1 6T70 and 6T75 front-drive transaxles. On the 6L80 that covers 2006-up Chevrolet, GMC and Cadillac trucks and SUVs plus the Camaro and Corvette. Sonnax notes that the 6T70 series dropped these switches in its later redesign, and that the later parts do not interchange, so a Gen 2 6T unit does not take this kit. If you are not sure which TEHCM you have, compare the switch layout on your unit to the kit before ordering, or send us your year and VIN. Matching 6L80 parts are on our 6L80 transmission page.
Drain the pan and drop the filter, then remove the TEHCM from the valve body; keep the bench clean, because dirt is what killed the old switches. Take off the switch retainer plate and remove the old laminates and seals. Clean the bores with solvent and dry them. Seat each new seal with the installer and plunger, lay each new laminate in place with the laminate tool, and reinstall the plate and module to the torque in your service manual. A fresh 6L80 filter and gasket kit belongs on the same job, and refill with Dexron VI. Clear codes, confirm the switch states read correctly in each range, then run the adapt relearn. If debris was the cause, look upstream for valve body wear; a 6L80E valve body upgrade kit addresses worn regulator circuits.
| Fits | GM 6L45, 6L50, 6L80, 6L90, Gen 1 6T70 and 6T75 |
| Replaces | 124740-TL30 |
| Includes | Laminate discs, seals, piston, seal plunger, seal installer, laminate installation tool, instructions |
| Material | Rubber seals, aluminum and stainless steel tools |
| Weight | 14.1 oz |
If a worn laminate or leaking seal in a TEHCM pressure switch is setting the code, rebuilding the switches fixes the cause. Rule out wiring, fluid level and low line pressure first.
The kit includes enough laminate discs and seals to rebuild one TEHCM, plus the installation tools, which you can reuse.
It fits the first-generation 6T70 and 6T75. Later redesigned 6T units dropped these pressure switches and do not use this kit.
No. You are keeping the same module and calibration. Clear codes, verify the switch states and run the transmission adapt relearn.
Dexron VI. Top off or refill after reinstalling the TEHCM and pan, then check the level hot following the service procedure.
