Gm Mode 22 Scan Tool By Terry |best| – Reliable

| PID Hex | Description | Why It Matters | | --- | --- | --- | | 0x1654 | Transmission Turbine Shaft Speed | Detects TCC slip or internal clutch failure | | 0x1655 | Transmission Output Shaft Speed | Calculate true gear ratio | | 0x1668 | Line Pressure (PSI) | Low pressure = worn pump or cross leaks | | 0x16B0 | Knock Retard (degrees) | False knock from loose converters vs real detonation | | 0x16C1 | Left & Right Fuel Trim Cell | Long-term cell correction (not seen in Mode 01) | | 0x16D3 | EGR Position Sensor (actual vs commanded) | Sticky EGR valves |

Its primary appeal is its ability to use Mode 22 to pull both standard and GM-specific PIDs. In its era, this was a significant advantage over basic code readers. By combining an ELM327 adapter with Terry's software, a DIY mechanic could access a level of vehicle data that would otherwise require a professional-grade, and much more expensive, scan tool.

Tailored for a quick overview of critical engine systems. Understanding OBD-II Mode 22: Enhanced Data

The software's standout feature was its use of GM's "Mode 22" diagnostic protocol. Unlike the standard OBD-II Mode 01, which provides generic, universally mandated data, Mode 22 unlocked access to GM's extended Parameter IDs (PIDs)—data points that are much more manufacturer-specific. This is what made it so valuable to GM owners. gm mode 22 scan tool by terry

What are you trying to track down? What OBD-II hardware adapter do you plan to use?

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

Since Terry’s original software was distributed via BBS (bulletin board systems) and early websites in the 1990s, it lives on through the GM tuning community. You can often find the executable and required cable schematics on: | PID Hex | Description | Why It

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

Terry’s Mode $22 tool usually operates via common hobbyist interfaces:

Here’s everything you need to know about using GM Mode 22 effectively. Tailored for a quick overview of critical engine systems

To utilize the GM Mode 22 Scan Tool by Terry, you need a functional diagnostic setup consisting of software, an interface converter, and a compatible vehicle. 1. Hardware Interface (The Adapter)

: Distributed as a free software utility for Windows-based PCs, making it a budget-friendly option for DIY enthusiasts.

Terry's software leverages Mode 22 to give you functioning live data that many generic code readers of the era simply could not access.

To understand the tool, you must understand the protocol. OBD2 systems support ten modes of operation, ranging from reading codes (Mode 03) to clearing them (Mode 04).