If you’re experiencing erratic shifting, a check engine light, or your 2008-2010 HUMMER H3 is stuck in limp mode, a failing Transmission Control Module (TCM) is the most common culprit. As a mechanic with over two decades of experience, I’ve seen how a faulty TCM can sideline even the most rugged vehicles. This isn’t just an annoyance; it’s a reliability issue that can leave you stranded. This OEM-quality T42 TCM, part number 24243921, is the definitive, hassle-free solution to restore your H3’s transmission performance and dependability.
The biggest headache with replacing electronic modules is the mandatory, and often expensive, trip to the dealership for programming. We eliminate that step entirely. We flash this module with the latest GM software and program it directly to your vehicle’s VIN before it ships. When it arrives, it’s a true plug-and-play part. You get a reliable fix that restores precise gear changes, proper torque converter lockup, and clears persistent transmission codes, all without leaving your driveway.
Case Study: The Elusive H3 Limp Mode
A customer brought in their 2009 H3 with an intermittent problem that was driving them crazy. The truck would randomly go into limp mode (stuck in 3rd gear) with a P0700 code, but after a restart, it would sometimes drive fine for days. They’d already replaced a shift solenoid with no luck. After connecting my scan tool and monitoring live data, I noticed the TCM was intermittently losing communication. Instead of a costly diagnostic rabbit hole, we ordered this pre-programmed TCM. The swap took less than 20 minutes, and the problem was solved permanently. It’s a classic example of how a direct-fit, correctly programmed module saves time, money, and frustration.
Is Your HUMMER H3 Showing These Telltale Signs?
A failing TCM doesn’t always mean a complete transmission failure. Often, the signs are electronic. If you’re noticing any of the following, it’s time to inspect your TCM:
- âś” Harsh, banging shifts or delayed gear engagement.
- âś” The vehicle is stuck in a single gear (limp mode) to protect the transmission.
- âś” An illuminated Check Engine Light or Transmission Warning Light.
- âś” Diagnostic Trouble Codes (DTCs) stored, such as P0700 (Transmission Control System Malfunction), P0750, or other solenoid-related faults.
- âś” A sudden drop in fuel economy due to inefficient shifting.
- âś” Complete loss of communication with the module, preventing shifting.
A Straightforward Guide to TCM Installation
Replacing the 2008-2010 HUMMER H3 TCM is a job most DIYers can handle in their own garage. For the H3, the module is conveniently located in the right-hand rear of the engine compartment, making access simple.
- Safety First: Always disconnect the negative terminal on your vehicle’s battery to prevent any electrical shorts and to help reset the system’s adaptive memory.
- Locate the Module: Find the TCM on the RH rear side of the engine bay. It will have several large electrical connectors attached.
- Disconnect and Remove: Carefully unplug the wiring harnesses. They have locking tabs that may need to be pressed or slid to release. Once disconnected, unbolt the module from its mounting bracket.
- Install the New Module: Bolt the new, VIN-programmed TCM into place. Securely plug in the wiring harnesses, ensuring each connector clicks firmly into place.
- Final Steps: Reconnect the battery terminal. While the module is pre-programmed, it’s good practice to use a basic OBD2 scan tool to clear any lingering fault codes from the ECU’s memory. Start the vehicle and test drive to confirm smooth shifting.
Verified Vehicle Compatibility List
This T42 TCM is a direct replacement for a wide range of General Motors vehicles equipped with 4-speed automatic transmissions like the 4L60E and 4L65E. It is interchangeable with part numbers 24252114, 24234503, 24243901, and more. While this page focuses on the 2008-2010 HUMMER H3 TCM, please confirm your vehicle is on the list below.
ALLURE 06-09 Transmission; (lower air cleaner housing)
AVALANCHE 1500 07-08 Transmission; (next to battery)
CANYON 08-12 Transmission; (RH rear engine compartment)
COBALT 06-10 Transmission; (LH strut tower)
COLORADO 08-12 Transmission; (RH rear engine compartment)
DTS 06-11 Transmission; (RH front engine compartment)
ENVOY 06-07 Transmission; (LH engine compartment), (8 cylinder)
ENVOY 08-09 Transmission; (LH engine compartment)
ENVOY XL 06 Transmission; (LH engine compartment), (8 cylinder)
EXPRESS 1500 VAN 06-14 Transmission; (RH engine compartment)
EXPRESS 2500 VAN 06-14 Transmission; (RH engine compartment)
EXPRESS 3500 VAN 06-14 Transmission; (RH engine compartment)
G5 07-10 Transmission; (LH strut tower)
G6 06-10 Transmission; (LH strut tower)
GRAND PRIX 06-08 Transmission; (lower air cleaner housing)
HHR 06-11 Transmission; (LH engine compartment)
HUMMER H3 08-10 Transmission; (RH rear engine compartment)
IMPALA 06-11 Transmission; (lower air cleaner housing)
ION 06-07 Transmission; (behind LH strut tower)
LACROSSE 06-09 Transmission; (lower air cleaner housing)
LUCERNE 06-07 Transmission; (4.6L), (LH engine compartment)
LUCERNE 08-11 Transmission; (LH engine compartment)
MALIBU 06-10 Transmission; (LH frame rail)
MONTE CARLO 06-07 Transmission; (lower air cleaner housing)
SAAB 9-7X 06-09 Transmission; (LH engine compartment)
SAVANA 1500 VAN 06-14 Transmission; (RH engine compartment)
SAVANA 2500 VAN 06-14 Transmission; (RH engine compartment)
SAVANA 3500 VAN 06-14 Transmission; (RH engine compartment)
SIERRA 1500 PICKUP 07 Transmission; (new style, smooth door skin), (next to battery)
SIERRA 1500 PICKUP 08-13 Transmission; (next to battery), w/o hybrid option
SILVERADO 1500 PICKUP 07 Transmission; (new style, smooth door skin), (next to battery)
SILVERADO 1500 PICKUP 08-13 Transmission; (next to battery), w/o hybrid option
SSR 05-06 Transmission; (front LH frame)
SUBURBAN 1500 07-08 Transmission; (next to battery)
TAHOE 07-09 Transmission; (next to battery)
TRAILBLAZER 06-09 Transmission; (LH engine compartment), (8 cylinder models for 06-07)
YUKON 07-09 Transmission; (next to battery)
YUKON XL 1500 07-08 Transmission; (next to battery)
Frequently Asked Questions
Do I need to take this part to a dealer for programming?
Absolutely not. We handle all the programming here before shipping. Just provide your vehicle’s VIN during checkout, and the module will arrive ready for plug-and-play installation.
Is there a core charge for my old TCM?
No, there is no core charge or need to return your old part. This simplifies the process for you, saving you time and return shipping costs.
Will this fix a P0700 trouble code?
A P0700 code is a general fault request from the TCM to the main engine computer. While this module often resolves the underlying issue causing the P0700, you should scan for more specific transmission codes (e.g., P07xx series) to confirm the diagnosis.
What if I have the wrong part number?
This module, 24243921, is a direct replacement for many other GM part numbers. As long as your vehicle is on our compatibility list, this module will function correctly, as it is the correct hardware family (T42) for your H3’s transmission.
What kind of warranty is included?
This Transmission Control Module is backed by our one-year warranty, giving you peace of mind and assurance in the quality and reliability of your repair.