Testing The Obd-M Malfunction Indicator Lamp (Mil); Guardian Strategy; Audio Warning System-3.0 Tks; Testing The Audio Warning System - Mercury/Mariner 3.0 MPI ECT Manual

The service engine icon or MIL will provide a visual indication of a malfunction with the engine's emission control system and
will remain illuminated while the OBD‑M fault is active.

Testing the OBD-M Malfunction Indicator Lamp (MIL)

1. Turn the ignition switch to the on position without cranking the engine.
2. The service engine icon and MIL will remain illuminated for four seconds if the visual indication 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.
Audio Warning System—3.0 TKS
Your Mercury MerCruiser power package may be equipped with an Audio Warning System. The audio warning system will not
protect the engine from damage. It is designed to warn the operator that a problem has occurred.
The audio warning system will sound with a continuous horn if one of the following occurs:
• Engine oil pressure too low
• Engine temperature too hot
• Sterndrive oil level too low
A continuous horn indicates a critical fault. Operating the engine during a critical fault can damage components. If the
warning horn emits a continuous beep, do not operate the engine unless avoiding a hazardous situation.
If the alarm sounds, stop the engine immediately. Investigate cause and correct it, if possible. If the cause cannot be
determined, contact your authorized Mercury MerCruiser dealer.

Testing The Audio Warning System

1. Turn the ignition switch to the "ON" position without cranking the engine.
90-8M0074347 OCTOBER 2012
eng
SC 1000 gauge and service engine light
NOTICE
Section 2 - Getting to Know Your Power Package
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