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
Among the DIY community, one specific utility has been a long-standing recommendation: the . What is GM Mode 22?
Many modern users have migrated to because it supports the same Mode 22 data stream but adds a modern interface, better graphing, and the ability to tune the PROM (EPROM) chips. However, purists still keep a copy of Terry’s original lightweight DOS tool on a bootable USB drive. gm mode 22 scan tool by terry
To appreciate Terry's scan tool, you must first understand the architecture of onboard diagnostics (OBD).
By mastering the Mode $22 protocol through Terry’s accessible tool, you save hours of diagnostic guesswork, protect your engine from dangerous tuning conditions, and gain a profound understanding of how General Motors powertrain control systems operate in the real world. These tools can read fault codes, monitor sensor
| Tool | Protocol | Price | Best For | |------|----------|-------|-----------| | | ALDL Mode 22 | Free | Budget, simple diagnostics | | Scan9495 | ALDL Mode 22 | $30 shareware | LT1/LT4 specific (94-95) | | TunerPro RT | ALDL + OBD-II | Free (donation) | Advanced tuning & logging | | ALDLLogger | ALDL Mode 22 | Free | Mac/Linux users | | Tech 1 w/ GM cartridge | All GM modes | $500+ used | Professional restoration |
The GM Mode 22 Scan Tool by Terry: Ultimate Guide to Advanced GM Diagnostics Many modern users have migrated to because it
Terry was a community programmer who recognized that professional tools like the Tech 1 or Vetronix Mastertech were expensive, rare, and locked to dealer use. He developed a software-based solution—often distributed as a freeware/shareware Windows application—that, when paired with a simple serial or USB-to-ALDL cable, could perform miracles. His tool demystified the $EE, $8D, $42, and $58 masks used in GM vehicles from the mid-80s to the mid-90s.
Plug your USB ALDL cable into the port. Pins A and B (top two rightmost pins) are typically the ground and data lines, but quality cables auto-detect.
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
Requests current, standardized powertrain live data.