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A brief note about Snapshot Data :

·       About: It is a set of critical parameters captured and stored by an individual ECU along with a DTC on the occurrence of specific criteria.

·       Freeze Frame Data is taken at the moment but snapshot is like a Video. 

·       Purpose: These parameters can help technician to understand possible root cause of DTC occurred and the condition in which DTC has occurred.

·       Storage Location: RAM and NVRAM

·       Vehicle manufacturer is responsible for defining:

o   Count: Number of Snapshot Records to store for a DTC (single or multiple)

o   Occurrence Criteria: When shall we store a Snapshot record

·       Content of Snapshot Data:

o   Every ECU can have different set of parameters which can be part of its Snapshot Data.

o   Vehicle Level Parameters: Vehicle Speed, Vehicle Odometer, Vehicle Mode, etc.

o   System Level Parameters: Sensor values, Systems environment data, System State values, etc.

·       Real World Example of Snapshot Data are as Below:

o   ABS ECU: Each Wheel Speed Sensor value, Brake Fluid Pressure, Master Cylinder Pressure/ each wheel pressure, vehicle speed, etc.

o   BMS ECU: Battery SOC/SOH, Battery Temperature (Cell/Pack temperatures, Coolant) Contactor statuses, Pack Level / Cell Level Current, Battery Internal resistance, Isolation /Insulation Resistance, etc. 

A Sampl A Sample Screen for a Snapshot Data for Throttle Position Sensor DTC  :

·            An ECU has captured 5 seconds data (before and after) the occurrence of DTC.

                A Diagnostic Tool displays freeze frame data in a graphical way for easy interpretation of the information

Events:


EEvents:

    1)     Throttle Position Sensor malfunction happens at Timestamp : 00:03:51

    2)     The sensor signal becomes unavailable since then. Due to 5 seconds of signal unavailability a DTC is logged by an ECU.

    3)     DTC P0120 - Throttle Position Sensor/Switch "A" Circuit Malfunction Circuit logged at

        Timestamp: 00:03:56.


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