Gm Mode 22 Scan Tool By Terry May 2026

GM Mode 22 Scan Tool by Terry is a free, legacy diagnostic software utility designed for use with ELM327-based hardware interfaces

to access enhanced diagnostic data from General Motors vehicles. Key Features and Capabilities

This tool specializes in proprietary GM diagnostic "Mode 22" requests, which provide deeper insight than standard generic OBD-II modes. Its primary functions include: Enhanced Data Access

: Reads ongoing sensor data and fault codes beyond basic emissions-related info, allowing users to view real-time data while driving. Sensor Monitoring : Displays a variety of parameters including: Engine RPM and Vehicle Speed. Coolant and Intake Air Temperatures. Fuel System Status and Fuel Pressure. Short/Long Term Fuel Trims. Timing Advance and Air Flow Rate. Absolute Throttle Position. Code Management

: Allows users to read and clear diagnostic trouble codes (DTCs) and reset the Check Engine Light (MIL). Technical Details Hardware Requirement

: Typically requires an ELM327 USB or Bluetooth interface to bridge the vehicle's computer and a PC. Software Design

: It was originally distributed as a lightweight, user-friendly program. Installation usually involves simply extracting files to a hard drive folder without a complex installer. Availability

: It is often found in the "downloads" or "free software" sections of OBD diagnostic resource sites

In-Depth Review of GM Mode 22 Scan Tool by Terry

The GM Mode 22 scan tool, developed by Terry, is a software-based diagnostic tool designed to interface with General Motors vehicles. This review aims to provide an exhaustive analysis of the tool's capabilities, features, and performance.

Overview

The GM Mode 22 scan tool is a Windows-based application that allows users to connect to a vehicle's onboard computer (ECU) via a compatible OBD-II interface. The tool provides access to various vehicle parameters, enabling users to diagnose and troubleshoot issues, as well as perform advanced functions.

Key Features

Mode 22 Support: The tool supports Mode 22, also known as "Service $22," which allows users to interact with the vehicle's ECU to perform advanced functions, such as reprogramming and configuring vehicle settings.
Multi-Vehicle Support: The GM Mode 22 scan tool supports a wide range of General Motors vehicles, including Chevrolet, Buick, GMC, and Cadillac models.
Parameter Monitoring: The tool provides real-time monitoring of various vehicle parameters, such as engine speed, coolant temperature, and transmission performance.
Trouble Code Reading: Users can read and clear diagnostic trouble codes (DTCs), allowing for efficient diagnosis and repair of issues.
Advanced Functions: The tool offers advanced features, including the ability to perform vehicle configuration and reprogramming.

User Interface and Experience

The GM Mode 22 scan tool features a user-friendly interface, with a logical and intuitive layout. The main dashboard provides quick access to essential functions, while the menu system allows users to navigate to more advanced features.

Connection Process: The tool's connection process is straightforward, with clear instructions provided for connecting to the vehicle's ECU.
Data Display: The tool displays data in a clear and concise manner, making it easy to interpret and analyze.

Performance and Compatibility

The GM Mode 22 scan tool performed well during testing, with reliable connections and accurate data readings.

Vehicle Compatibility: The tool supports a wide range of General Motors vehicles, including newer models with more advanced ECUs.
Stability and Reliability: The tool demonstrated stability and reliability during testing, with minimal crashes or errors.

Comparison to Other Scan Tools

The GM Mode 22 scan tool stands out from other scan tools on the market due to its: gm mode 22 scan tool by terry

Cost-Effectiveness: The tool offers advanced features at a competitive price point, making it an attractive option for DIYers and professionals.
Specialized Features: The tool's support for Mode 22 and advanced functions sets it apart from more basic scan tools.

Conclusion

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.

Rating: 4.5/5

Recommendation:

The GM Mode 22 scan tool is recommended for:

DIYers and enthusiasts looking for a cost-effective, advanced diagnostic tool
Professional mechanics and technicians working on General Motors vehicles
Anyone seeking a reliable and feature-rich scan tool for troubleshooting and repairing vehicle issues

Limitations:

The tool requires a compatible OBD-II interface and Windows-based computer
Some advanced features may require additional hardware or software

Future Development:

The developer, Terry, has expressed plans to continue updating and improving the GM Mode 22 scan tool. Future updates may include:

Expanded vehicle support
Additional advanced features
Improved user interface and experience

Overall, the GM Mode 22 scan tool by Terry is a valuable resource for anyone working on General Motors vehicles. Its advanced features and reliable performance make it a worthwhile investment for DIYers and professionals alike.

The Terry GM Mode 22 Scan Tool has become a legendary piece of kit for enthusiasts of late-90s and early-2000s General Motors vehicles. Unlike generic code readers that only provide surface-level data, this specialized tool taps into the specific proprietary "Mode 22" diagnostics used by GM. If you are looking to diagnose a misfire, check real-time sensor data, or perform advanced maintenance on a classic LS-based engine or a 3800 Series V6, this tool is often the most cost-effective bridge between a basic scanner and a professional Tech 2.

The core appeal of Terry’s tool is its ability to access PID (Parameter ID) data that most budget scanners simply cannot see. Mode 22 is a specific request mode used by GM controllers to broadcast high-speed, live data. While a standard OBD-II scanner might show you a generic oxygen sensor reading, Terry’s setup allows you to monitor individual cylinder misfire counts, transmission line pressure, and torque converter slip in real-time. This level of granularity is essential for tracking down intermittent issues that don’t always trigger a Check Engine Light.

Setting up the scan tool typically requires a compatible interface cable and a laptop running the specific software developed and refined by the community. It is favored by the DIY crowd because it prioritizes function over form. The interface is lean and designed for performance, ensuring that data lag is minimized—a crucial factor when you are tuning a vehicle or trying to catch a momentary dip in fuel pressure.

One of the standout features often cited by users is the misfire monitor. GM’s Mode 22 data is famous for being incredibly sensitive. By using this tool, a mechanic can see if Cylinder 4 is having a slight "hiccup" even if the engine feels smooth to the touch. This allows for proactive maintenance, like replacing a single failing ignition coil or spark plug wire before it leaves you stranded or damages your catalytic converter.

Furthermore, the tool is a staple for those performing engine swaps. When putting a modern GM drivetrain into an older chassis, communication between the various control modules can be tricky. Terry’s tool helps verify that the PCM is receiving the correct signals from the rest of the vehicle, making it an indispensable part of the "LS swap" toolkit.

In a world where automotive software is increasingly locked behind subscriptions and expensive handheld units, the GM Mode 22 Scan Tool by Terry remains a testament to the power of community-driven diagnostics. It provides professional-grade insights for the price of a few parts, ensuring that older GM vehicles stay on the road and perform at their peak. Whether you are a weekend warrior or a dedicated tuner, having this tool in your garage changes the way you interact with your vehicle's computer.

The GM Mode 22 Scan Tool by Terry is a specialized, often free software utility designed for deep-level diagnostics on General Motors vehicles, typically used in conjunction with low-cost ELM327 OBD2 interfaces. Overview of the Tool

Unlike generic OBD2 scanners that only read "Mode 01" global data, this tool targets Mode 22, a manufacturer-specific diagnostic mode used by GM to provide access to enhanced data parameters (PIDs) not available through standard protocols.

Platform Compatibility: It is frequently bundled with ELM327 USB or Bluetooth diagnostic kits as part of a free software suite. GM Mode 22 Scan Tool by Terry is

Target Audience: It is primarily aimed at DIY enthusiasts and older GM vehicle owners who

Key Capability: It enables users to view proprietary sensor data that generic tools might miss, such as specific transmission temperatures, ABS data, or body control module (BCM) status. Functionality Comparison

While "Terry's" tool is a lightweight utility, it sits between basic code readers and professional factory equipment: OBD II Generic PID Diagnosis - MOTOR Information Systems

Unlock the Full Potential of Your Vehicle with the GM Mode 22 Scan Tool by Terry

Are you tired of throwing money at your vehicle's problems without really knowing what's going on under the hood? Do you want to take control of your car's maintenance and repairs, but don't know where to start? Look no further than the GM Mode 22 scan tool by Terry, a powerful diagnostic tool that's designed specifically for General Motors vehicles.

In this article, we'll take a closer look at the GM Mode 22 scan tool, what it can do, and how it can help you diagnose and fix problems with your vehicle. We'll also explore the benefits of using this tool, and what sets it apart from other scan tools on the market.

What is the GM Mode 22 Scan Tool?

The GM Mode 22 scan tool is a handheld device that's designed to connect to your vehicle's OBD-II port, allowing you to access a wide range of diagnostic information and perform various tests. The tool is specifically designed for General Motors vehicles, including cars, trucks, and SUVs.

The GM Mode 22 scan tool is based on the work of Terry, a well-known DIY enthusiast and mechanic who's been developing and refining his own scan tool solutions for years. The tool is designed to be easy to use, even for those with limited technical expertise, and provides a wealth of information and functionality that's not available with standard OBD-II scan tools.

What Can the GM Mode 22 Scan Tool Do?

The GM Mode 22 scan tool is a highly advanced diagnostic tool that offers a wide range of features and functions. Some of the key capabilities of the tool include:

Mode 22 data streaming: The tool allows you to access and stream data from your vehicle's engine control module (ECM), transmission control module (TCM), and other systems. This data can be used to diagnose problems, monitor system performance, and make adjustments as needed.
Trouble code reading and clearing: The tool can read and clear trouble codes from your vehicle's ECM, TCM, and other systems. This allows you to quickly identify problems and make repairs, and also reset the check engine light.
Live data streaming: The tool provides live data streaming from your vehicle's sensors and systems, allowing you to monitor performance in real-time.
Bi-directional control: The tool offers bi-directional control, allowing you to send commands to your vehicle's systems and monitor the results.
Component testing: The tool allows you to perform component tests, such as testing the fuel pump, ignition system, and other components.

Benefits of Using the GM Mode 22 Scan Tool

There are many benefits to using the GM Mode 22 scan tool, including:

Cost savings: By using the tool to diagnose and repair problems yourself, you can save money on labor costs and avoid expensive trips to the dealership or repair shop.
Increased control: The tool gives you direct access to your vehicle's systems and data, allowing you to take control of maintenance and repairs.
Improved diagnosis: The tool provides a wealth of information and data that can help you diagnose problems more accurately and quickly.
Enhanced performance: By using the tool to monitor and adjust your vehicle's systems, you can optimize performance and improve fuel efficiency.

What Sets the GM Mode 22 Scan Tool Apart?

The GM Mode 22 scan tool is a unique and powerful diagnostic tool that's designed specifically for General Motors vehicles. Here are a few things that set it apart from other scan tools on the market:

Specificity: The tool is designed specifically for GM vehicles, which means it's optimized for the unique systems and protocols used by GM.
Advanced features: The tool offers a wide range of advanced features, including mode 22 data streaming, bi-directional control, and component testing.
Ease of use: The tool is designed to be easy to use, even for those with limited technical expertise.
Support: The tool is supported by a community of DIY enthusiasts and mechanics who share knowledge, tips, and resources.

Conclusion

The GM Mode 22 scan tool by Terry is a powerful diagnostic tool that's designed to help you take control of your vehicle's maintenance and repairs. With its advanced features, ease of use, and specificity for GM vehicles, this tool is a must-have for anyone who wants to get the most out of their vehicle.

Whether you're a DIY enthusiast, a mechanic, or just someone who wants to save money on repairs, the GM Mode 22 scan tool is an essential tool to have in your toolkit. So why wait? Get your GM Mode 22 scan tool today and start unlocking the full potential of your vehicle! Mode 22 Support : The tool supports Mode

Additional Resources

If you're interested in learning more about the GM Mode 22 scan tool or want to purchase one, here are some additional resources to check out:

Terry's website: Terry's website is a great resource for learning more about the GM Mode 22 scan tool and other DIY projects.
GM Mode 22 scan tool forums: There are several online forums dedicated to the GM Mode 22 scan tool, where you can connect with other users, ask questions, and share knowledge.
YouTube tutorials: There are many YouTube tutorials and videos available that can help you learn how to use the GM Mode 22 scan tool and diagnose problems with your vehicle.

By taking the time to learn about and use the GM Mode 22 scan tool, you can save money, increase your control over your vehicle's maintenance and repairs, and optimize performance. So don't wait – get started today!

The GM Mode 22 Scan Tool by Terry is a specialized freeware diagnostic utility designed primarily for Windows and legacy mobile platforms. It is frequently bundled as a complementary software option for ELM327-based Bluetooth and USB scan tools. Key Features and Capabilities

While modern professional scanners like the FOXWELL NT510 Elite offer comprehensive bi-directional controls, this tool serves as a lightweight alternative for specific GM diagnostics:

Platform Support: The software is compatible with Windows, OSX, and older mobile operating systems such as PalmOS and Pocket PC.

Enhanced Mode 22 Access: It is designed to utilize the "Mode 22" diagnostic request, a proprietary GM protocol used to retrieve specific data parameters (PIDs) that standard generic OBD-II Mode 01 requests may not cover.

Core Diagnostic Functions: Like most ELM327-compatible software, it allows users to: Read and clear diagnostic trouble codes (DTCs). Monitor real-time engine data and sensor values. Detect specific system pressures and status indicators.

Portability: Due to its small file size (approx. 1.49Mb), it is easy to install and deploy on older hardware. Limitations ELM327 Software - Interfuse LLC.

How It Works: The "Terry" Difference

Unlike modern generic scan tools that use a standard J1850 or CAN bus, Terry’s tool sends a specific Mode 22 request frame 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.

Why is this a big deal? Because the "Terry" interpretation accounts for the unique scaling and addressing used by each GM ECM. A generic tool might just display "MAF = 127," but Terry’s tool knows that raw value of 127 actually means 12.7 grams/second. That level of specific calibration is why enthusiasts still seek out this tool.

Understanding the GM Mode 22 Scan Tool by Terry: A Gateway to Early GM Diagnostics

For owners and technicians working on 1980s to mid-1990s General Motors vehicles (especially those with the 8192-baud ALDL data stream), the "GM Mode 22 Scan Tool by Terry" remains a legendary piece of DIY diagnostic software. Unlike generic code readers that only retrieve "Check Engine" codes, Terry's tool provides a deep, real-time look into the inner workings of early GM electronic control modules.

Step-by-Step: Diagnosing a Torque Converter Clutch (TCC) Issue with Mode 22

Terry’s classic case: “Customer says RPM jumps 200-300 RPM on the highway. No codes.”

Step 1 – Connect & Enter Enhanced Mode
On your scanner, select “GM Enhanced” or “Manufacturer Specific.” Choose the PCM (engine/transmission module).

Step 2 – Select Mode 22 PIDs
Do not use “All Data.” Hand-pick:

Engine RPM (Mode 01 or 22 – either works)
TCC Slip (Mode 22 PID 0x1656 on most LS1-based PCMs)
Transmission Input Shaft Speed
Transmission Output Shaft Speed

Step 3 – Road Test with Graphing
Drive at steady 50-55 mph in 4th gear. Command TCC lockup via scanner (bi-directional function). Watch the TCC Slip PID.

0-20 RPM slip – Healthy
50-150 RPM slip – Worn TCC clutch
Over 200 RPM slip – TCC regulator valve or PWM solenoid issue (common in 4L60E)

Step 4 – Verify with Gear Ratio
Using Input Shaft RPM / Output Shaft RPM:

4th gear locked should be ~0.70:1 ratio. If it’s ~0.75:1 but slip PID says 0, you have a failed sensor or wrong PID definition.

“That’s the power of Mode 22,” says Terry. “Generic data would show RPM and VSS, but you’d never see the slip. You’d replace the torque converter unnecessarily.”