Storing and Erasing Freeze Frame Data

Government regulations require that the engine operating conditions be captured whenever the MIL is illuminated. The data captured is called Freeze Frame data. The Freeze Frame data is very similar to a single record of the operating conditions. Whenever the MIL is illuminated, the corresponding record of the 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 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 throttle position angle
^ The manifold absolute pressure and barometric pressure
^ The base pulse width of the fuel injection
^ The loop status

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