Long post, cut and paste from Mercruiser service manual. Please note the number of items that will cause the 2bpm alarm.
Also note they are all engine sensor related, not CO or gas fume alarms.
Greg
GENERAL INFORMATION SERVICE MANUAL NUMBER 36
Page 1A-24 90-864573 FEBRUARY 2002
Engine Guardian System
General Description
Engine Guardian is the focal point of the self-diagnostic strategy on these engines. It helps
protect the engine from possible damage that could result from several faulty conditions.
The system monitors the sensors incorporated on the engine and if a malfunction is
discovered, a fault description is stored in thePCMand available power is normally reduced.
By ensuring that engine output is at a low enough level, the engine is better protected from
thermally induced failures.
For example, if an open or short is found in any sensor, available power will be reduced to
90% of total, the AudioWarning System Alarmwill sound 2 beeps perminute (2 Bp/min) and
the Smartcraft gauges will display a warning lamp. In a seawater pump pressure low
condition, the maximum rpm will vary with the pressure and temperature of the engine and
could be limited to idle in extreme cases of overheating, a constant beep will sound and
Smartcraft gauges will display a warning lamp.
IMPORTANT: Engine Guardian cannot guarantee that engine damage will not occur
when adverse operating conditions are encountered. Engine Guardian is designed
to warn the operator of an adverse condition and to reduce power by limiting rpm in
an attempt to reduce possible engine damage. The boat operator is ultimately
responsible for proper engine operation.
SERVICE MANUAL NUMBER 36 GENERAL INFORMATION
90-864573 FEBRUARY 2002 Page 1A-25
Warning Chart
The engine warning system incorporates an audio alarm and, if installed, Smartcraft
Gauges System. When the key switch is turned to the ON position, the audio alarm will
momentarily activate to test thewarning system. The alarm should sound once if the system
is operable. This table is a guick guide, showingwhat warning output will accompany a fault.
Fault Smartcraft
Gauges
Audio
Alarm
Available
Power
Description
ECT CKT HI Yes 2 Bp/min 90% Open
ECT CKT LO Yes 2 Bp/min 90% Short
ECT Coolant
Overheat
Yes Constant 6 - 100 % Engine guardian
overheat condition
EST 1 Open 1 Yes 2 Bp/min 100% Coil harness wire open
EST 1 Short 1 Yes 2 Bp/min 100% Coil harness wire short
Fuel Injector 1-7-4-6
Open
Yes 2 Bp/min 100% Fuel injector wire open
Fuel Injector 3-5-2-8
Open
Yes 2 Bp/min 100% Fuel injector wire open
Guardian Strategy Yes Constant 0% - 100% Protection Strategy
IAC Output LO/HI 2 Yes 2 Bp/min 90% Open
Knock Sensor 1 Lo Yes 2 Bp/min 90% Open
Knock Sensor 1 Hi Yes 2 Bp/min 90% Short
Low Drive Lube
Strategy
Yes Constant 100% Low oil in sterndrive
Low Oil Pressure
Strategy
Yes Constant 0 - 100% Low oil pressure strategy
NOTE: If any 5v sensor becomes shorted to ground the engine will not start. If the engine
is operating when the short occurs the engine may stop operating and will not start.
NOTE: 1 GM EFI ignition system failure open or shorted, driver will flag EST 1 fault.
NOTE: 2 TPS must see 5% throttle then back to 0% to flag IAC fault.
NOTE: 3 2-wire sensor open will read sensor Hi on scan tool.
NOTE: 4VDC PWR Low - if shorted or no voltage engine will not start; if VDC PWR voltage
falls velow 22 volts will set sensor faults.
NOTE: 5 Shift Switch - will activate code when engine rpm are above 3500 rpm and 40%
load.
GENERAL INFORMATION SERVICE MANUAL NUMBER 36
Page 1A-26 90-864573 FEBRUARY 2002
Warning Chart (continued)
Fault Smartcraft
Gauges
Audio
Alarm
Available
Power
Description
Main Power Relay
Output
Yes No N/A Engine will not start
Main Power Relay
Backfeed
Yes No N/A Engine will not start
MAP Sensor 1 Input
High
Yes 2 Bp/min 90% High voltage or short
MAP Sensor 1 Input
Low
Yes 2 Bp/min 90% Open, no visual on
SC1000
Oil PSI CKT Hi Yes 2 Bp/min 90% Open, defaults to 50.7 psi
Oil PSI CKT Lo Yes 2 Bp/min 90% Short, defaults to 50.7 psi
Overspeed Yes Constant rpm limit Engine over rpm limit
Pitot CKT Hi No No 100% Short or high voltage
Pitot CKT Lo No No 100% Open
Sea Pump PSI Lo Yes Constant 6-100%
Guardian Strategy
Sea Pump CKT Hi Yes 2 Bp/min 90% Open - 0 psi reading
Sea Pump CKT Lo Yes 2 Bp/min 90% Voltage high or short
Sea Water Temp No No N/A Defaults to --31 degreesC
Fuel Level #1 No No N/A Only if turned on
STB EMCT CKT Hi N/A N/A N/A N/A
STB EMCT CKT Lo N/A N/A N/A N/A
STB EMCT CKT
Overheat
N/A N/A N/A N/A
NOTE: If any 5v sensor becomes shorted to ground the engine will not start. If the engine
is operating when the short occurs the engine may stop operating and will not start.
NOTE: 1 GM EFI ignition system failure open or shorted, driver will flag EST 1 fault.
NOTE: 2 TPS must see 5% throttle then back to 0% to flag IAC fault.
NOTE: 3 2-wire sensor open will read sensor Hi on scan tool.
NOTE: 4VDC PWR Low - if shorted or no voltage engine will not start; if VDC PWR voltage
falls velow 22 volts will set sensor faults.
NOTE: 5 Shift Switch - will activate code when engine rpm are above 3500 rpm and 40%
load.
SERVICE MANUAL NUMBER 36 GENERAL INFORMATION
90-864573 FEBRUARY 2002 Page 1A-27
Warning Chart (continued)
Fault Smartcraft
Gauges
Audio
Alarm
Available
Power
Description
Steer CKT Hi No No 100% Short or high voltage
Steer CKT Lo No No 100% Open
TPS1 CKT or
Range Hi
Yes 2 Bp/min 90% Short or high voltage
TPS1 CKT or
Range Lo
Yes 2 Bp/min 90% Open or low voltage
Trim CKT or Range
Hi
Yes No 100% Open or high voltage
Trim CKT or Range
Lo
Yes No 100% Short
5 VDC PWR Low 4 Yes 2 Bp/min 90% Short or low - engine
may not start
MAT Sensor Hi Yes 2 Bp/min 90%
Open -
default to --32 degrees F
MAT Sensor Lo Yes 2 Bp/min 90%
Short -
default to --32 degrees F
Shift Switch 5 Yes 2 Bp/min 90% Open Circuit
NOTE: If any 5v sensor becomes shorted to ground the engine will not start. If the engine
is operating when the short occurs the engine may stop operating and will not start.
NOTE: 1 GM EFI ignition system failure open or shorted, driver will flag EST 1 fault.
NOTE: 2 TPS must see 5% throttle then back to 0% to flag IAC fault.
NOTE: 3 2-wire sensor open will read sensor Hi on scan tool.
NOTE: 4VDC PWR Low - if shorted or no voltage engine will not start; if VDC PWR voltage
falls velow 22 volts will set sensor faults.
NOTE: 5 Shift Switch - will activate code when engine rpm are above 3500 rpm and 40%
load.