"GM Mode 22 Scan Tool by Terry" is a lightweight, Windows-based terminal application. It acts as a specialized bridge between an ELM327-based interpreter chip and a GM vehicle's data bus (primarily J1850 VPW or early CAN bus configurations). Software Profile : Freeware. Developer : Terry. Platform Support : MS Windows (XP, Vista, 7, 8, 10).

Mode 22 is primarily found on GM vehicles from ~1996 to 2006 (pre-CAN bus transition), covering:

Terry warns about three common traps:

Designed to work with cheap, widely available ELM327 Bluetooth or USB interfaces.

| Tool | Mode 22 Support | Price | Ease of Use | |------|----------------|-------|--------------| | Terry’s Tool | Yes (older GM) | Free | Moderate (requires PC) | | Tech 2 | Full | $500–2000 | High | | Autel MaxiDiag | Partial (some PIDs) | $500+ | High | | Torque Pro + custom PIDs | Limited (requires manual PID entry) | $5 | Medium |

: Due to its small file size (approx. 1.49Mb), it is easy to install and deploy on older hardware. Limitations ELM327 Software - Interfuse LLC.

By taking the time to learn about and use the GM Mode 22 scan tool, you can save money, increase your control over your vehicle's maintenance and repairs, and optimize performance. So don't wait – get started today!

is the most powerful modern equivalent. It uses the same Mode 22 principle but adds a visual dashboard, custom definition files (XDFs), and live checksums. However, many old-school mechanics still reach for Terry’s tool because it requires no configuration—plug and play for most $8D and $EE masks.

The GM Mode 22 Scan Tool by Terry is a legacy, free software utility designed to access manufacturer-specific diagnostic data (Mode 22h PIDs) on older General Motors vehicles. It operates with ELM-based OBD-II interfaces to monitor ECU and TCM parameters, though it lacks support for modern CAN FD protocols and is strictly limited to data retrieval. For a list of free OBD-II software options, including this tool, see Interfuse LLC. OBD-II free software - OBDTester

The "GM Mode 22 Scan Tool by Terry" is more than just a piece of outdated software; it is a digital artifact representing a critical moment in automotive history. It was a direct predecessor to the powerful and user-friendly diagnostic tools we have today, such as the Torque app for Android. This freeware project helped prove that a dedicated hobbyist with an ELM327 adapter could accomplish what was once the exclusive domain of professional mechanics with expensive factory scan tools.

Enter . According to veteran technician Terry, “Mode 22 isn't just another data stream—it's the backdoor into GM’s proprietary brain. If you don't know how to use it, you're diagnosing blind.”