Propulsion Control Module (PCM)
PCM 112 Controller
All engine models with or without emission control have a 112‑pin propulsion control module (PCM) to manage closed‑loop
engine operation based on oxygen sensor feedback. The battery power requirements of the new PCM requires the use of a
separate PCM power harness for clean power. This new PCM allows fault maintenance that conforms to the onboard
diagnostics ‑ marine (OBD‑M) requirements mandated by California Air Resource Board (CARB) regulations.
The PCM 112 ignition system consists of a battery, PCM 112 controller, main power relay (MPR), fuse, crankshaft position
sensor (CPS), ignition coil harnesses, ignition coils, spark plug wires, and spark plugs.
The PCM 112 controls all ignition system functions, and constantly adjusts dwell and spark timing. It uses engine speed and
position information from the crankshaft to control the sequence, dwell, and timing of the spark. The PCM 112 also monitors
information from various sensor inputs that include the following:
• The throttle position sensor (TPS)
• The engine coolant temperature (ECT) sensor
• The manifold air temperature (MAT) sensor
• The manifold absolute pressure (MAP) sensor
The ignition coil driver controls the ignition coils. The PCM 112 sends a signal to the ignition coil driver to complete the ground
path for the coil primary winding 12‑volt power source. After the proper dwell time has been reached, the PCM 112 signal is
removed from the driver and the ground path for the coil primary winding is opened, causing the ignition coils to fire.
PCM Removal and Installation
!
WARNING
Performing service or maintenance without first disconnecting the battery can cause product damage, personal injury, or
death due to fire, explosion, electrical shock, or unexpected engine starting. Always disconnect the battery cables from the
battery before maintaining, servicing, installing, or removing engine or drive components.
Electrical Components
90-8M0099748 eng DECEMBER 2015 © 2016 Mercury Marine Page 4E-5
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