PCM is Powertrain Control Module. Its function on a HMMWV M1152 would be minimal, if it has one (I don't know. Maybe?). I have no idea what might be...
Hummer H1, as Robyn suggests, or HMMWV M1152 (Humvee)? They are not the same. The HMMWV will not have a PMD to worry about, and will also have a 24V...