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Understanding the 10 OBD Modes: How Your OBD2 Scanner Unlocks Vehicle Data

By Joseph Kim
Published on March 11th, 2025

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Modern vehicles are packed with advanced computer systems, and OBD2 scanners serve as the key to accessing crucial diagnostic information. But did you know that OBD2 scanners operate using 10 different diagnostic modes?

Each mode provides specific data about your vehicle’s performance, emissions, and potential issues. Whether you're a DIYer or a professional, understanding these 10 OBD modes can help you make better use of your Innova OBD2 scanner.

Let’s break down what each mode does and how it helps you diagnose your vehicle.

Mode 1: Request Live Data (Real-Time Monitoring)

This mode provides real-time data from the vehicle’s sensors, components, and systems, giving you a live snapshot of its performance. You can monitor parameters such as:

Engine RPM
Coolant temperature
Fuel system status
Oxygen sensor readings
Throttle position
...

Why It Matters: Live data helps diagnose performance issues on the spot, making it easier to spot irregularities and potential problems.

Mode 2: Freeze Frame Data

When a fault occurs and triggers the Check Engine Light (CEL), Mode 2 stores a "snapshot" of the conditions at the time of the fault. This includes:

Engine load
Vehicle speed
Engine temperature
Fuel system status
...

Why It Matters: This mode helps you understand what was happening when the fault occurred, which is crucial for pinpointing the root cause of an issue.

Mode 3: Stored Diagnostic Trouble Codes (DTCs)

This mode retrieves diagnostic trouble codes (DTCs) stored by the vehicle’s onboard computer. These codes help identify specific issues related to the engine, emissions, and other vital components.

Why It Matters: Knowing the trouble codes allows you to diagnose problems accurately and take appropriate action.

Mode 4: Clear Diagnostic Trouble Codes & Reset Check Engine Light

After repairs are completed, Mode 4 allows you to erase the stored DTCs and turn off the CEL.

Why It Matters: Clearing codes helps verify if the issue has been resolved. However, if the problem persists, the code may reappear.

Mode 5: Oxygen Sensor Monitoring Test results (non CAN vehicles only)

This mode was used in no CAN vehicles to check the oxygen sensor’s performance. It’s now replaced by Mode 6 in OBD2 systems.

Why It Matters: Understanding oxygen sensor data is still crucial for diagnosing fuel efficiency and emissions problems.

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Mode 6: On-Board Monitoring Test results (Advanced Test Results)

Mode 6 provides manufacturer-specific test results from various sensors and components.

Misfire Monitors
Fuel System Monitor
Catalyst Converter Monitor
Oxygen Sensor Monitor
Evaporate (EVAP) system Monitor
Exhaust Gas Recirculation (EGR) System Monitor
Secondary Air Monitor

Why It Matters: This mode helps catch issues that may not yet trigger a CEL but could affect long-term vehicle health.

Mode 7: Pending Diagnostic Trouble Codes

While Mode 3 retrieves stored DTC, Mode 7 checks for pending DTC—issues that have been detected but haven’t met the conditions to turn on the Check Engine Light yet.

Why It Matters: Identifying pending codes early can help prevent future breakdowns or emissions test failures.

Mode 8: Control of Onboard Components/Systems

This mode allows the scanner to activate certain vehicle components for testing purposes. Some functions include:

Turning on the radiator fan
Testing fuel pump operation
Running the EVAP system leak test

Why It Matters: Professional technicians use this mode for advanced diagnostics, confirming if components are functioning properly.

Mode 9: Vehicle Information (VIN, Calibration IDs, etc.)

Mode 9 retrieves important vehicle information, including:

Vehicle Identification Number (VIN)
ECU Calibration Number
In-Use Performance Tracking (IPT)

Why It Matters: Professional technicians use this mode for advanced diagnostics, confirming if components are functioning properly.

Mode 10: Permanent Diagnostic Trouble Codes

Unlike Mode 3, which retrieves stored DTC, Mode 10 shows permanent DTCs that can only be erased once the vehicle’s onboard system confirms the issue is resolved through multiple drive cycles.

Why It Matters: Permanent codes ensure that emissions-related problems are fixed before they disappear from the system, preventing tampering.

Final Thoughts

Understanding these 10 OBD modes helps you get the most out of your Innova OBD2 scanner. Whether you're troubleshooting a CEL, monitoring real-time performance, or ensuring your vehicle passes an emissions test, these modes provide critical insights into your vehicle’s health.

Looking for a scanner that supports all these modes? Check out our latest Innova OBD2 scanners for accurate and reliable diagnostics.

Innova OBD2 Scanners