Freeze Frame Data
ECM stores the engine and driving conditions (in the form of data as shown in the figure) at the moment of the detection of a malfunction in its memory. This data is called "Freeze frame data".
Therefore, it is possible to know engine and driving conditions (e.g., whether the engine was warm or not, where the vehicle was running or stopped, where air / fuel mixture was lean or rich) when a malfunction was detected by checking the freeze frame data. Also, ECM has a function to store each freeze frame data for three different malfunctions in the order as the malfunction is detected. Utilizing this function, it is possible to know the order of malfunctions that have been detected. Its use is helpful when rechecking or diagnosing a trouble.
Priority of freeze frame data:
ECM has 4 frames where the freeze frame data can be stored. The first frame stores the freeze frame data of the malfunction which was detected first. However, the freeze frame data stored in this frame is updated according to the priority described. (If malfunction as described in the upper square "1" is detected while the freeze frame data in the lower square "2" has been stored, the freeze frame data "2" will be updated by the freeze frame data "1".)
| Priority | Freeze frame data in frame 1 |
|---|---|
| 1 | Freeze frame data at initial detection of malfunction among misfire detected (P0300 - P0304), fuel system too lean (P0171) and fuel system too rich (P0172) |
| 2 | Freeze frame data when a malfunction other than those in "1" is detected |
In the 2nd through the 4th frames, the freeze frame data of each malfunction is stored in the order as the malfunction is detected.
In case freeze frame data for a pending DTC are stored, when no malfunction is detected in the next driving cycle and the ignition switch is turned to OFF, the freeze frame data are cleared.
Shown in the table are examples of how freeze frame data are stored when two or more malfunctions are detected.
| Frame | Frame 1 | Frame 2 | Frame 3 | Frame 4 | |
|---|---|---|---|---|---|
| Malfunction detection order | Freeze frame data | 1st freeze frame data | 2nd freeze frame data | 3rd freeze frame data | |
| 1 | No malfunction detected | - | - | - | - |
| 2 | P0401 (Pending DTC) | P0401 data | P0401 data | - | - |
| 3 | No malfunction detected | P0401 data | P0401 data | - | - |
| 4 | No malfunction detected | - | - | - | - |
| 5 | P0111 (Pending DTC) | P0111 data | P0111 data | - | - |
| 6 | P0111 P0402 (Pending DTC) | P0111 data | P0111 data | P0401 data | - |
| 7 | P0300 (Pending DTC) | P0300 data | P0111 data | P0401 data | P0300 data |
| 8 | P0300 | P0300 data | P0111 data | P0300 data | - |
-: No freeze frame data
Freeze frame data clearance:
The freeze frame data is cleared at the same time as clearance of diagnostic trouble code (DTC) and pending DTC.