OBD2 Modes

📖 YOUCANIC Automotive Glossary

OBD2 Modes (Service Modes)

OBD2 defines ten standardized diagnostic service modes (Mode $01 through Mode $0A) that specify different types of diagnostic data a scan tool can request from the vehicle’s ECU. Mode $01 (Live Data) returns real-time sensor and calculated values. Mode $02 (Freeze Frame) returns the snapshot of data stored when a DTC was set. Mode $03 (Confirmed DTCs) returns all active/stored diagnostic trouble codes. Mode $04 (Clear DTCs) commands the ECU to erase all codes, freeze frame data, and reset monitors. Mode $05 (O2 Sensor Monitoring) returns oxygen sensor test results. Mode $06 (Non-Continuous Monitor Results) returns raw test values and thresholds for onboard monitoring tests. Mode $07 (Pending DTCs) returns codes detected in the last drive cycle but not yet confirmed. Mode $08 (Component Control) allows bidirectional control of onboard components. Mode $09 (Vehicle Information) returns VIN, calibration IDs, and software version data. Mode $0A (Permanent DTCs) returns codes that cannot be cleared by a scan tool.

Most DIYers interact with Modes $01, $02, $03, $04, and $07 during routine diagnostics without realizing they’re using specific OBD2 modes — your scanner’s menu labels like “Read Codes,” “Live Data,” “Freeze Frame,” and “Clear Codes” correspond directly to these modes. However, understanding the complete mode structure helps you unlock the full potential of your scanner. Mode $06 is particularly powerful for advanced diagnostics (see the Mode $06 Data glossary entry), and Mode $09 is essential for parts lookup because it retrieves the full 17-character VIN, ECU calibration ID, and CVN (Calibration Verification Number) used to confirm the ECU hasn’t been improperly modified. Mode $08 (bidirectional control) allows scanners to command components to activate — for example, turning on the fuel pump, firing individual injectors, cycling the EVAP purge valve, or operating the EGR valve — which is invaluable for confirming component operation during diagnosis. Not all scanners support all modes, and not all vehicles respond to all modes. Basic code readers typically only support Modes $01, $03, $04, and $07, while professional scanners like the YOUCANIC UCAN-II support all ten modes plus manufacturer-specific enhanced modes that go beyond the OBD2 standard to access transmission, ABS, airbag, and body control module diagnostics.