While professional dealership tools like the GM Tech2 cost thousands of dollars, a developer known simply as released a free, lightweight software utility that could "talk" to GM vehicles using this specialized mode. The Story of a DIY Legend
Mode 22 provides access to specific that generic scanners cannot see. This includes critical transmission data (like fluid temperature and gear slip), individual wheel speed sensors for ABS troubleshooting, fuel trim data for specific engine banks, and oil life monitoring. By targeting Mode 22, Terry’s tool unlocked professional-level insights for the average user. Accessibility and Community Impact
These tools can read fault codes, monitor sensor data, and conduct various tests to identify issues with the engine, transmission, Vehicle Diagnostic Scan Tool By BLUETOOTH... From 1,89
A proprietary, enhanced diagnostic mode defined under SAE J2190.
Using the tool effectively requires precise execution to avoid communication timeouts on the vehicle network. gm mode 22 scan tool by terry
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
A developer and enthusiast named Terry created a custom PC-based software script and interface mapping. It targeted the exact memory addresses and Mode 22 PIDs (Parameter IDs) used by GM vehicles. Often distributed as a lightweight executable, an Excel-based macro tool, or an open-source script, the tool allowed users to pair a basic hardware interface with a laptop to extract professional-grade data. Key Features and Capabilities
Requests current, standardized powertrain live data.
Standard OBD tools update data 2 to 5 times per second. Terry’s tool optimizes the communication baud rate, enabling high-speed logging of specific Mode $22 parameters. This speed is critical for catching intermittent misfires or tracking transient knock during tuning runs. 3. Module-Specific Interrogation While professional dealership tools like the GM Tech2
While "Terry" likely stopped development on this project around 2004, its impact is still felt today. It paved the way for a vibrant community of DIYers who reverse-engineered GM's PIDs, many of which are now compiled in community-maintained lists and CSV files for apps like Torque.
To help you get the most out of your diagnostic setup, tell me a bit more about your current project: What of GM vehicle are you working on?
Connect your compatible OBD-II pass-through device to the vehicle's diagnostic port under the steering column. Launch Terry’s custom software interface on your laptop, mobile device, or dedicated micro-display. Step 2: Protocol Selection
View every analog and digital input the ECM sees: Using the tool effectively requires precise execution to
Mode 22 unlocks manufacturer-specific codes that do not illuminate the Check Engine light but cause drivability issues. Examples include:
Depending on the specific version of the script or software patch you deploy, it generally supports:
Tracks exact, historical misfires before they trigger a Check Engine Light.
The tool is highly compatible with the standard ELM327 Bluetooth interface, which connects your GM vehicle to a Windows laptop or Android device.
Load the specific PID configuration file (.csv or .txt) matching your vehicle's engine architecture (e.g., LS1 V8, 3800 V6, or Duramax Diesel). This populates the software with human-readable labels instead of raw hex codes. Step 4: Live Data Interrogation
The GM Mode 22 scan tool by Terry is a powerful and versatile diagnostic tool designed for General Motors vehicles. Its advanced features, user-friendly interface, and reliable performance make it an excellent choice for DIYers and professionals.