Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Emission-Related Freeze Frame Data
Freeze frame data allows access to emission-related values from specific generic PIDs. These values are stored when an emission-related diagnostic trouble code (DTC) is stored in continuous memory. This provides a snapshot of the conditions that were present when the DTC was stored. Once 1 set of freeze frame data is stored, this data remains in memory even if another emission-related DTC is stored, with the exception of misfire or fuel system DTCs. Once freeze frame data for a misfire or fuel system DTC is stored, it overwrites any previous data, and freeze frame data is no longer overwritten. When a DTC associated with the freeze frame data is erased or the DTCs are cleared, new freeze frame data can be stored again. In the event of multiple emission-related DTCs in memory, always note the DTC for the freeze frame data.
| Acronym | Description | Measurement Units |
|---|---|---|
| ECT | Engine Coolant Temperature | Degrees |
| FUELSYS1 | Open/Closed Loop1 | OL/CL/OL DRIVE/OL FAULT/CL FAULT |
| LONGFT1 | Long Term Fuel Bank1 | % |
| LOAD | Calculated Load Value | % |
| RPM | Engine RPM | RPM |
| SHRTFT1 | Short Term Fuel Bank1 | % |
| VSS | Vehicle Speed | km/h-mph |
Some unique parameters (PIDs) are stored in the keep alive memory (KAM) of the powertrain control module (PCM) to help in diagnosing the root cause of misfires. These PIDs are collectively called misfire freeze frame (MFF) data. These parameters are separate from the generic freeze-frame data that is stored for every malfunction indicator lamp (MIL) code. They are used for misfire diagnosis only. The MFF data is more useful for misfire diagnosis than the normal diagnosis only. It is captured at the time of the highest misfire rate and not when the DTC is stored at the end of a 1,000 or 200 revolution block. (Generic freeze-frame data for misfire can be stored minutes after the misfire actually occurred.)
| PID Name | Description | Measurement Units |
|---|---|---|
| MFF RPM | Engine RPM at the time of misfire | RPM |
| MFF LOAD | Engine load at the time of misfire | PERCENT |
| MFF VS | Vehicle speed at the time of misfire | MPH/KPH |
| MFF IAT | Intake air temperature at the time of misfire | DEGREES |
| MFF SOAK | Engine-off soak time at the time of misfire | MINUTES |
| MFF RNTM | Engine running time at the time of misfire | SECONDS |
| MFF TP | Throttle position at time of misfire | VOLTAGE |
| MFF T CNT | Number of driving cycles at the time of misfire (at least one 1,000 rev block) |
Number of TRIPS |
| MFF PNP | 1= in drive during the time of misfire | MODE |
| MP LRN | 1= misfire wheel profile learned in KAM | NONE |
NO RELATED
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.