Here is the completed circuit tracing for an IDM 120
with the top and bottom traces overlaid. Green traces
are on the bottom, red in the inner layers and blue on
the top layer. Components are black.
The component count is around 300 test points, 140
capacitors, 140 resistors, 40 diodes, 25 transistors and
20 integrated circuits.
The main circuits are:
12VDC input circuit
5 VDC supply for the IC's
Circuits for decoding the injector firing signals
from the PCM.
Generating the low-voltage control signals to the
various switching transistors
110 V injector boost-mode power supply & storage
Hi-voltage switching circuit to control power to the
injectors on the left and right cylinder banks
Hi-voltage switching circuit to control the ground
circuits to the individual injectors
Error diagnostic and reporting circuits