MerCruiser 3.0 MPI, Owner'S Manual

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Section 2 - Getting to Know Your Power Package
Page 32 90-899883272 MARCH 2008
OBDM
If an OBDM fault is detected, the audio warning system sound with one five‑second horn,
then one short, 1/2‑second horn every 60 seconds for certain faults related to the emissions
or fuel system. See your authorized Mercury MerCruiser dealer for assistance.
33404
a
OFF
ON
5 60 60 60
½ ½ ½
ON ON ON
OFF OFF
b
a - Horn (on or off)
b - Time (in seconds)
Testing The Audio Warning System
1. Turn the ignition switch to the "ON" position without cranking the engine.
2. Listen for the audio alarm. The alarm will sound if the system is functioning correctly.
Guardian Strategy
Engine Guardian reduces the potential for engine damage by restricting engine power
when the PCM detects a potential problem. Below are some examples of what Engine
Guardian monitors:
• Oil pressure
• Engine overspeed
• Exhaust manifold temperature
IMPORTANT: Guardian can reduce power anywhere from 100% to idle, depending on the
severity of the problem. If forced to idle, boat speed might not respond to throttle operation.
The PCM stores the fault for diagnostics. For example, if the water inlet becomes partially
blocked, Guardian reduces the available power level of the engine to help prevent damage
from decreased water flow to the engine. If the debris passes through, and full water flow
is restored, Guardian restores engine power to normal. To avoid recurrence of the problem,
contact an authorized Mercury MerCruiser dealer.
As another example, Transmission Guardian is a MerCruiser DTS feature that protects
transmissions from clutch damage. Transmission Guardian monitors the clutch pack
pressure in forward and reverse gears. If the transmission fluid pressure drops below a
predetermined level, Transmission Guardian lowers the engine torque and speed to
prevent clutch slippage. To avoid possible recurrence of the problem, you should contact
an authorized dealer. The ECM stores the fault and with this information the technician will
be able to more rapidly diagnose problems.