Freeze Frame is an element of the Diagnostic Executive that stores engine operating conditions at the moment an emission-related fault is stored in memory (when the MIL is commanded on). This data can be used to help identify the cause of an emissions-related fault.
Regulations related to the OBD II System require that certain engine-operating conditions be captured and stored whenever the MIL is illuminated. The data captured is called Freeze Frame data. This data can be thought of as a single record of a certain set of operating conditions. Whenever the MIL is turned on, the corresponding record of operating conditions is recorded to the Freeze Frame buffer.
The Freeze Frame data can only be overwritten by data associated with a Fuel Trim or Misfire fault because data from these faults takes priority over data associated with any other type of fault. The Freeze Frame data will not be erased unless the associated History DTC is cleared.