Spent a little time and rebuilt, actually built a new, stimulator to replace the old 'PCB in a vise' model.  The old guy worked but was getting pretty ragged with all the modifications made to it.  This new one as an audio driver and internal speaker so we can debug the audio portion of the ECM-555.  The power supply has also been reconfigured to mimic what is actually in the car.  This is needed to debug the power hold feature where the ECM decides when to remove power from itself.

The new Main schematic.
The main audio driver, Block_O_Audio.jpg.
The headphone driver, Block_L_Audio.jpg.