This chips uses a different encoding compared to hitag. It seems to use for reader communication Binary Pulse Length Modulation (BPLM) as well. However, the number of carrier periods for a 0 (24 periods) and a 1 (56 periods) differ from those of Hitag2. Check page 12, 13 and 14 of the e5561 datasheet.
Interesting that you are looking into these immobilizer chips. Let us know if you are developing code that allows communication with these chips. We would encourage you to share it with the proxmark3 community.
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