28C256 EEPROMs will work in ECUs, but require pins to be moved around/altered due to them being a different pinout than either 27 C256 or 29 C256 chips.

Datasheet for an Atmel 28C256 (PDF)

 name:         28C256
 function:     32k x 8 paged parallel EEPROM
 package:      DIP-32,32
 pinout:

      +------()------+
  A14 | 1          28| VCC
  A12 | 2          27| WE
   A7 | 3          26| A13
   A6 | 4          25| A8
   A5 | 5          24| A9
   A4 | 6          23| A11
   A3 | 7   28256  22| OE
   A2 | 8          21| A10
   A1 | 9          20| CE
   A0 |10          19| I/O7
 I/O0 |11          18| I/O6
 I/O1 |12          17| I/O5
 I/O2 |13          16| I/O4
  GND |14          15| I/O3
      +--------------+