This is from one of FS1's pages......
This Engine Computer also referred to as an Engine Control Module (ECM), Engine Control Unit (ECU) & Powertrain Control Module (PCM) is guaranteed to fit all 1998 Jeep Cherokee models with a 4.0L engine size. The following part numbers are compatible with this unit:
56041531AA, 56041531AB, 56041531AC, 56041531AD, 56041531AE, 56041531AF, 56041532AA, 56041532AB, 56041532AC, 56041532AD, 56041532AE, 56041532AF, 56041534AA, 56041534AB, 56041534AC, 56041534AD, 56041534AE, 56041534AF, 56041534AG, 56041534AH, 56041535AA, 56041535AB, 56041535AC, 56041535AD, 56041535AE, 56041535AF, 56041537AA, 56041537AB, 56041537AC, 56041537AD, 56041537AE, 56041537AF, 56041537AG, 56041537AH, 56041544AA, 56041544AB, 56041544AC, 56041544AD, 56041544AE & 56041544AF