Storing and Erasing Freeze Frame Data

Government regulations require that engine operating conditions be captured whenever the Malfunction Indicator Lamp (MIL) is illuminated. The data captured is called freeze frame data. The freeze frame data is very similar to a single record of operating conditions. Whenever the MIL is illuminated, the corresponding record of operating conditions is recorded to the freeze frame buffer.

Each time a diagnostic test reports a failure, the current engine operating conditions are recorded in the freeze frame buffer. A subsequent failure will update the recorded operating conditions. The following operating conditions for the diagnostic test which failed typically include the following parameters:

^ Air Fuel Ratio
^ Air Flow Rate
^ Fuel Trim
^ Engine Speed
^ Engine Load
^ Engine Coolant Temperature
^ Vehicle Speed
^ TP Angle
^ Manifold Absolute Pressure (MAP)/Barometric Pressure (BARO)
^ Injector Base Pulse Width
^ Loop Status

Freeze frame data can only be overwritten with data associated with a misfire or fuel trim malfunction. Data from these faults take precedence over data associated with any other fault. The freeze frame data will not be erased unless the associated history DTC is cleared.