Freeze frame explained
When the engine computer stores a fault, it also saves a snapshot of the engine’s readings at that moment: the freeze frame. It tells you the conditions the fault happened in.
Updated
What a freeze frame is
A freeze frame is one set of readings, saved together with the fault code that caused it. It doesn’t show what happened before or after, only that moment.
The rules require at least one frame. As a rule it belongs to the first fault the car stored. A later misfire or fuel system fault may take its place, because those are the most useful to have a snapshot of. Some cars store more frames, but a generic tool reads the required one.
So the freeze frame doesn’t always belong to the code you’re looking at. Read My Car shows it with the fault it belongs to, under “Freeze frame” in that fault’s details.
What it contains
Which readings are saved depends on the car. Read My Car asks for these, and shows the ones your car saved:
- Calculated engine load
- How hard the engine was working, from idle to full load.
- Coolant temperature
- Whether the engine was cold, warming up or warm.
- Engine speed and vehicle speed
- Idling, pulling away, or driving at speed.
- Fuel trim
- How much the engine computer was correcting the fuel. Positive means adding fuel, negative taking fuel away.
- Intake manifold pressure, air flow, throttle position
- The air going into the engine, on cars that report them.
- Intake air temperature, timing advance, battery voltage
- Where the car saved them.
How to read it
Ask a few questions of the snapshot. The answers narrow down the cause, and tell a mechanic how to reproduce the fault.
- Cold or warm? A fault that only sets on a cold engine points elsewhere than one on a warm engine.
- Idle or driving? Zero speed at idle speed means the car was standing still.
- Light or heavy load? A fault under heavy load, such as a misfire when accelerating hard, points to something that struggles under strain.
- What were the fuel trims doing? As a general guide they stay within about ±10 % on a healthy engine. Large positive values with a lean code mean the engine was adding fuel to make up for too much air or too little fuel.
Read My Car marks freeze-frame readings that are clearly outside normal operation, the same way it does in live data, such as fuel trims beyond ±10 % or a coolant temperature above 112 °C.
Try it on a demo car
Both demo cars in the app have a freeze frame. The 2011 Volkswagen Golf stored it for P0171, system too lean: the engine was warm, the car was driving at about 72 km/h, and both fuel trims were well above +10 %, so the engine was adding fuel, as a lean code says. The 2004 Peugeot 307 HDi stored one for P0401, too little exhaust gas recirculation.
Clearing erases it
Clearing the fault codes erases the freeze frame too. Write it down or take a screenshot first if a mechanic may need it.
The car can also erase it by itself: once a fault hasn’t come back for a number of warm-ups or drives, the code and its freeze frame may be removed.
Questions
Why does the freeze frame belong to a different code?
As a rule the car keeps one frame, for the first fault it stored, unless a misfire or fuel system fault replaces it. Read My Car shows it with the fault it belongs to.
Why is there no freeze frame?
The codes may have been cleared, the car may have erased an old fault by itself, or the car doesn’t report one for that fault. Not every code comes with a frame.
Is a freeze frame a recording of the drive?
No, it’s one moment. To see how readings change over a drive, record live data to a CSV file in Read My Car.