Though largely superseded by modern apps and GDS2 software , "GM Mode 22 Scan Tool by Terry" remains a nostalgic name for anyone who spent their weekends in a garage with a bulky laptop and a dream of fixing their own Chevy or Buick.
Unlike modern generic scan tools that use a standard J1850 or CAN bus, Terry’s tool sends a specific to the ECM. The ECM responds by dumping a packet of 32–64 bytes of raw RAM data. Terry’s software then decodes that raw hex data into human-readable values.
The GM Mode 22 scan tool performed well during testing, with reliable connections and accurate data readings. gm mode 22 scan tool by terry
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.”
Released entirely free of charge, the last known stable version is 1.5, which the developer created to obtain both standard and extended Parameter Identifiers (PIDs) from a vehicle's computer. Despite a modest file size of just 1.49 MB, the software represented a significant leap in accessibility for DIY mechanics. Though largely superseded by modern apps and GDS2
Mode $22 allows a scan tool to request specific data parameters (PIDs) directly from individual electronic control modules (ECUs). This includes data from the: Powertrain Control Module (PCM) Transmission Control Module (TCM) Body Control Module (BCM) Electronic Brake Control Module (EBCM/ABS)
One of the tool's strongest points is its ability to graph and display (Block Learn Memory) and INT (Integrator) values. These numbers tell you if the engine is running rich or lean and, more importantly, why the computer thinks it is. This is invaluable for diagnosing vacuum leaks, faulty oxygen sensors, or fuel delivery problems. Terry’s software then decodes that raw hex data
This points to electrical interference or a loose OBD2 port pin. Ensure your diagnostic cable is securely fastened and routed away from the vehicle's ignition coils or plug wires.
It bypasses generic restrictions to show exact sensor voltages, raw counts, and fluid temperatures. Key Features of Terry's Tool
: The software is compatible with Windows, OSX, and older mobile operating systems such as PalmOS and Pocket PC.