Category Archives: Forester Diesel

ROM Differences JZ2F401A vs JP3F501A

Those MY2009/10 Impreza (110 kW) and Forester (108 kW) ROMs are almost identical.

Binary comparison result: Only 1292 bytes differ.
Spreadsheet (exported from Calc) can be downloaded here: Rename to .zip and extract! Update: File position listed by cmp starts at one instead of zero. This hasn’t been corrected in the XLS file yet.


Difference list was created using standard Unix command cmp, then imported into Spreadsheet application.
Unix/Linux terminal commands:

cmp -l "$file1" "$file2" > Impreza_JZ2F401A_vs_Forester_JP3F501A.txt

Important: cmp outputs file position in decimal, starting at one, content bytes in octal!
Result looks like this, three columns: address (dec), byte1 (oct), byte2 (oct)

16389 132 120
16390 121 106
16391 62 63

1047482 127 114
1047483 66 203
1047484 244 11

Apps like Calc can import such text file. Then you might want to use available functions like DEC2HEX, OCT2HEX, CHAR, … for number conversions.

Injection Quantity Limit (Gear)

Note: Following 3D table only represents a small part of the calculations the firmware performs. Lots of code plus data determine target torque and injection quantity. We currently don’t have the resources in order to analyze the whole thing.

3D-map, valid for these Boxer Diesel models at least:

2009 Impreza JZ2F302A 66 44 D8 71 07 22611AP282
2009/2010 Impreza JZ2F401A 66 44 D8 72 07 22611AP283
2009/2010 Forester JP3F501A 61 44 D8 72 07 22611AP203

So far content is 100% identical in those. Data type is uint8.

2008 Legacy J2TF230A, ROMID 58 44 D8 71 07, has minor differences. Ex: f(850, 6). Data type is int16.

For XML file go to page RomRaider ECU Definitions