6L80 / 6L90 TEHCM Guide: Common Failures, Tag IDs, and Year Differences

The 6L80 and 6L90 TEHCM (Transmission Electro-Hydraulic Control Module) is the brains and hydraulics of your GM six-speed automatic. It’s responsible for shift logic, line pressure control, and torque converter lockup—and when it fails, the results can range from harsh shifts to limp mode. This guide breaks down common issues, year differences, and how to identify your TEHCM by its Tag ID.

Quick links: Shop 6L80 / 6L90 TEHCMs • Monster TEHCM Finder Tool • Contact Tech Support

What the TEHCM Does

GM combined the valve body, solenoids, pressure switches, and TCM into a single unit known as the TEHCM. It mounts directly to the valve body inside the pan and uses a pressure manifold to regulate clutch apply and line pressure. This integration makes the transmission smarter but also introduces unique failure points if fluid quality or electronics degrade.

Common 6L80 / 6L90 TEHCM Failures

• Pressure Switch Failure: The internal switch membranes crack, causing erratic shift timing and codes like P0877 or P2715.
• TCC Slip or No Lockup: Common on 2006–2010 units where converter apply solenoids stick or command logic fails under heat.
• Limp Mode / Hard Shifts: Usually due to loss of pressure sensor feedback (P0796, P0777). Often mistaken for mechanical issues.
• Internal Short or Fluid Intrusion: Circuit board contamination from ATF causes permanent failure of the module or corrupted data.
• Incorrect Programming: Installing the wrong year or tag ID TEHCM can result in no crank or no gear engagement.

Year & Tag ID Differences (Quick Reference)

GM revised the 6L80/6L90 TEHCM several times between 2006 and 2020. Tag IDs identify both hardware and software versions. Installing the wrong one can cause a no-start or limp mode condition. Below is a simplified breakdown based on our Monster TEHCM Finder data:

How to Identify Your TEHCM

• Remove the transmission pan and locate the silver ID sticker on the TEHCM assembly.
• The Tag ID (e.g., 24256861) will be printed near the barcode.
• Match your Tag ID and year using our TEHCM Finder Tool before ordering.
• Check connector style — early versions use black 20-pin, later models use grey 20-pin sealed connectors.

Installation & Programming Tips

1. Always reprogram after installation. Use GM SPS2 or Techline Connect to marry the module to your VIN.
2. Perform a “Fast Learn” or “Reset Adapts” after reflash to ensure proper shift adaption.
3. Flush or replace the cooler to remove debris from pressure switch failure.
4. Use DEXRON VI only. Contaminated fluid shortens sensor life and corrupts internal circuits.

FAQ

Do I have to program a new TEHCM?
Yes — the TEHCM must be programmed to your vehicle VIN before the transmission will start or shift.

Can I swap TEHCMs between years?
No. The calibration and logic vary by Tag ID and year — mismatching them causes immediate limp mode.

Why do I have multiple solenoid and pressure codes?
That’s a classic internal circuit failure. The fix is replacing the TEHCM, not the valve body.

What fluid should I use?
Only DEXRON-VI full synthetic — it’s the only approved fluid for proper solenoid function and thermal control.

Helpful Links

• Monster 6L80E / 6L90E TEHCM Finder
• Shop TEHCMs
• ACDelco Techline Connect — official GM programming
• HP Tuners — advanced calibration and diagnostics