(OBD MODE 4)

Mode 4 (Clear / Reset Diagnostic information )

This mode is generally used to reset the MIL indicator (or "check engine light") after the vehicle has been worked on to make repairs, etc. This mode has no PIDs. It consists of the three header bytes, the mode byte (which is 04 hex), and the CRC or checksum byte. The vehicle returns three header bytes, the mode byte (which is 44 hex) and the CRC or checksum byte.

Please note that a mode 4 request will Clear ALL diagnostic data as well as the trouble codes, so be sure you have retrieved any on board test results that you may want to look at before you use mode 4.

Mode 4 causes the vehicle to clear or reset the following data. The modes/Pids that are used to access the data before clearing it are included for reference. Note that some of the modes and pids mentioned may not be supported on a particular vehicle.

Number of Trouble Codes (Mode 1 Pid 1)
All Diagnostic Trouble Codes (Mode 3)
Freeze Frame Trouble Codes (Mode 1 Pid 2)
All Freeze Frame Data (Mode 2)
Oxygen Sensor test data (Mode 5)
On Board Monitoring Test Status (Mode 1 Pid 1)
On Board Monitoring Test Results (Mode 6 and Mode 7)

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