Storing and Erasing Freeze Frame Data

Government regulations require that the engine operating conditions are to be captured whenever the MIL is illuminated. The data that is 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 failure records 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:

^ The Air Fuel Ratio
^ The Air Flow Rate
^ The Fuel Trim
^ The Engine Speed
^ The Engine Load
^ The Engine Coolant Temperature
^ The Vehicle Speed
^ The TP Angle
^ The MAP/BARO
^ The Injector Base Pulse Width
^ The Loop Status

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