To use the GM Mode 22 Scan Tool by Terry, you need proper hardware. The tool is software; the interface is what matters.
Do not use “All Data.” Hand-pick:
If you’ve spent any time under the hood of a late-90s to mid-2000s General Motors vehicle, you’ve likely run into the limitations of generic OBD-II scanners. They’ll give you a check engine light code, but they won’t tell you why a 4L60E transmission is slipping or why the ABS light triggers on a bumpy road. gm mode 22 scan tool by terry
Early versions were DOS or early Windows based, but more refined versions (often packaged as "TTS DataMaster" or similar, with Terry’s foundational logic) include the ability to to a file and play it back. This allows you to drive the car, record a stumble or misfire, and then review the data frame-by-frame later.
Car manufacturers build highly specific, proprietary diagnostic modes into their ECUs for assembly line testing and dealership service bays. For General Motors, this is (often written as Mode 22 or Mode $22). To use the GM Mode 22 Scan Tool
Start the engine and initiate the log. When troubleshooting performance issues, keep a close eye on the relationship between variables. For example, if you notice a sudden drop in spark advance, you can immediately check the Mode $22 knock sensor counters to see exactly which cylinder is detecting detonation. Why Terry’s Tool is Essential for the GM Community
Once you have the software and cable, follow this guide: They’ll give you a check engine light code,
While finding a working version on modern hardware is a challenge, and its functionality is far surpassed by today's apps, its core mission lives on. It remains a beloved piece of history for the GM enthusiasts who used it to turn their laptops into powerful diagnostic hubs, effectively writing a new chapter in the story of DIY car repair.
To use the GM Mode 22 Scan Tool by Terry, you need three components:
| 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 |
It is designed to work with affordable interfaces (like the OBDLink MX+ or specialized USB-to-OBD cables), making professional-level data accessible for the price of a few tanks of gas. Why You Need It for Tuning and Troubleshooting