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.
| 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 | gm mode 22 scan tool by terry
Standard OBD-II protocols are designed for emissions testing and basic engine data. However, manufacturers like GM and Ford use to transmit more detailed information through the CAN network. Unlike modern generic scan tools that use a
View every analog and digital input the ECM sees: | Tool | Mode 22 Support | Price