Freeze frame data
Workshop glossary › Diagnostics & protocols · UpdatedA snapshot of engine sensor values captured at the exact moment a DTC was stored. Critical for diagnosing intermittent faults.
Freeze frame is a snapshot the ECU takes the first time a DTC sets. It captures the engine speed, load, coolant temperature, fuel trims, vehicle speed, and a handful of other PIDs that were live at the moment of the fault. It is mandated by OBD-II Mode 02.
For intermittent problems — the customer says "it only does it on the motorway when it's cold" — the freeze frame is the most useful single piece of data on the scan tool. If short-term fuel trim was +25% and engine load was high when a P0171 (lean bank 1) stored, you can focus on metered air sources at high vacuum demand instead of guessing.
Only one freeze frame is stored at a time on most ECUs, and it is overwritten by higher-priority faults (anything that makes the MIL flash). Pull it before clearing codes.