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General Information About Mercruisers Warning System Horns On EFI Engines.
Here's some general information I have put together about the warning horn systems on Mercruiser EFI engines.
I hope this information will be able to help out the members of performance boats forums someday.
The 2 beeps per minute can be generated by quite a few things. Some of the error conditions will limit the available power the engine produces. The 2 beeps/minute can be generated by: cam sensor open or shorted, engine cooling temperature circuit open or shorted, coil harness wire (EST) open or shorted, fuel injector open or shorted, IAC output, knock sensor, MAP sensor, MAT sensor, oil pressure circuit open or shorted, port/starboard exhaust manifold cooling temperature circuit open or shorted, sea pump circuit open or shorted, fuel pump relay, throttle position sensor circuit open or shorted, low 5 volt power supply as well as other errors.
Best suggestion for the 2 beeps per minute is to have the dealer/shop read out the error log to see what is generating the error condition.
This table below is a guick guide, showing what warning horn output will accompany a fault for the Sterndrive (MCM) Model Serial Number 496 MAG HO 0M000000 and Above/496 MAG 0M000000 and Above.
PS, for all the non 496/8.1 EFI engines, Your particular EFI engine may not not have every one of these Warning horn Fault sensors, But most of the newer style EFI engines from Mercruiser now has a lot of these sensors that are listed below. The best thing to do is to have a service manual from mercruiser for your engine to help you know what your engine really has as far as sensors go.
Also it highly recommended that if you could buy a marine scan tool from Rinda technologies, it will help aid you with diagnosing your warning horns, if your going to be working on your own EFI engines this is a must have tool.
Warning system Faults, SC1000 Yes/No, Audio Alarm, Available Power %, Description.
(1) Cam Sensor Yes 2 Bp/min 90% Open or short, engine must be cranking to set this fault code.
(2) ECT CKT HI Yes 2 Bp/min 90% Open
(3) ECT CKT LO Yes 2 Bp/min 90% Short
(4) ECT Coolant Overheat Yes Constant 6-100 % Engine guardian overheat condition
(5) EST 1-8 Open Yes 2 Bp/min NA Coil harness wire open
(6) EST 1-8 Short Yes 2 Bp/min NA Coil harness wire short
(7) Fuel Injector 1-8 Open Yes 2 Bp/min NA Fuel injector wire open.
(8) Fuel Injector 1-8 Short Yes 2 Bp/min NA Fuel injector wire short
(9) IAC Output Yes 2 Bp/min 90% Only with rpm
(10) Knock Sensor 1 Yes 2 Bp/min 90% Alarm sounds for 20 seconds in NEUTRAL and indefinitely in gear.
(11) Knock Sensor 2 Yes 2 Bp/min 90% Alarm sounds for 20 seconds in NEUTRAL and indefinitely in gear.
(12) Low Drive Lube Strategy Yes Steady Bp 0-100% Low oil in sterndrive.
(13) Low Oil Pressure Strategy Yes Constant 0-100% Low oil pressure strategy.
(14) MAP Sensor 1 Input High No 2 Bp/min 90% Short, no visual on SC1000.
(15) MAP Sensor 1 Input Low No 2 Bp/min 90% Open, no visual on SC1000.
(16) MAT Sensor Yes 2 Bp/min 90% Open or short in MAT circuit.
(17) Oil PSI CKT Hi Yes 2 Bp/min 90% Short, defaults to 51.7 psi.
(18) Oil PSI CKT Lo Yes 2 Bp/min 90% Open, zero oil pressure.
(19) Overspeed Yes Constant RPM Limit Engine over rpm limit
(20) Port EMCT CKT Hi Yes 2 Bp/min 90% Open, defaults to 32 degrees F.
(21) Port EMCT CKT Lo Yes 2 Bp/min 90% Short, defaults to 32 degrees F.
(22) Port EMCT CKT Overheat Yes Constant 6-100% Overheat condition, 212
degreesF(100 degrees C) limit.
(23) Sea Pump PSI Lo Yes Constant 6-100% Low water pressure strategy, defaults to 43.4 psi.
(24) Sea Pump CKT Hi Yes 2 Bp/min 90% Open.
(25)Sea Pump CKT Lo Yes 2 Bp/min 90% Short.
(26) STB EMCT CKT Hi Yes 2 Bp/min 90% Open, defaults to 32 degrees F.
(27) STB EMCT CKT Lo Yes 2 Bp/min 90% Short, defaults to 32 degrees F.
(28) STB EMCT CKT Overheat Yes Constant 6-100% Overheat condition, 212 degrees (100 degrees C) limit.
(29) Steer CKT Hi Yes No No Open and short.
(30) TPS1 CKT Hi Yes 2 Bp/min 90% Short, signal to 5v+, engine will not start. Refer to data monitor screen.
(31) TPS1 CKT Lo Yes 2 Bp/min 90% Open.
(32) TPS 1 Range Hi Yes 2 Bp/min 90% Above 4.8v, 994 counts.
(33) TPS 1 Range Lo Yes 2 Bp/min 90% Below 0.5v, 35 counts.
(34) Trim CKT Hi Yes No No Short, high range, visual warning on SC1000 only.
(35) Trim CKT Lo Yes No No Open, low range, visual warning on SC1000 only.
(36) 5 VDC PWR Low Yes 2 Bp/min varies Short any 5v+ to ground.
Here's some other information that what will sound the alarm on a mercruiser Engine.
Constant tone alarms are for:
1.) engine coolant temp overheat,
2.) low engine oil pressure,
3.) engine overspeed,
4.) exhaust manifold cooling temp overheat
5.) sea pump PSI low.
Note #5 is known to be a common problem, It's been said that this fault might not show up in the fault history section of the scan tool.
If that is the case then the only other way to know if this is your problem, is to watch this sensor live as it happens out on the water with the scan tool hooked up to the engine.
Also make sure all the Battery cables are clean & tight plus a fully charged Battery is very important.
Check the water pressure sensor threads for any paint, Also check the sensor to see if it has come loose or Has a blockage of some kind.
If any sensor has lost it's ground it could sound the alarm. As an additional test, try adding a ground wire to the sensor threads to possibly stop the warning horn.
There is also a chance that you could have picked up or created some air bubble for a short time, until the boat slowed down, possibly due to the brass water pump impeller Housing could be failing due to deep grooves inside housing creating a disturbance with the water flow.
Constant beep alarms are for:
1.) low outdrive lube level.
Two Alarm beeps every 60 seconds are for:
1.) Faulty cam,
5.) knock sensors.
6.) open/short in the engine cooling temp circuit
7.) open/short in fuel injector wiring circuit,
8.) open/short in oil PSI circuit,
9.) open/short in exhaust manifold cooling temp circuit,
10.) open/short in sea pump circuit,
11.) open/short in throttle position circuit.
Good luck to you all.
Plug reading 101 by Mike Canter