Mercruiser 5.0 MPI Cat / 1 beep per minute but no code.

[Searay205]

Hello, I have an 2012 Mercruiser 5.0 mpi with catalyst. Boat runs perfect. I get a single beep once per minute only when engine running, not when key is just on. I checked with my Rinda and no codes were found under diagnostics or freeze frame. Does anybody have any idea why the horn would sound and not set a code? I changed the IAC last summer so I am doubtful that is it. I notice my IAC shows above 0% when off idle, should it be closed? If throttle plate is open the IAC is not needed. Boat maintenance is up to date. Seawater pressure, temperature, oil pressures all look great. Appreciate any ideas.

 

[alldodge]

This is where your thread should be, but you started another in the electric section. Mods will probably be along to combine

https://forums.iboats.com/forum/gen...ser-5-0-mpi-cat-1-beep-per-minute-but-no-code

The one beep is what most call a soft warning. The newer motors need good clean power being feed to the PCM. Check your battery cable connections on both ends and assure they are clean and tight.

Measure the battery voltage at the battery after the motor has been turned off and off a battery charger for at least 30 minutes. Voltage should be close to 12.V

 

[Searay205]

Thanks!!! I will check. I have service manual #49 which shows diagnostics but it doesn't show acceptable ranges. For example it explains high exhaust manifold temperature but doesn't specify what value/temperature is high. Sorry for posting in wrong section still trying to figure out forum. I appreciate the info, all the post I saw referenced two beeps per minute but mine is only one. When I was playing with my oxygen sensors I was surprised if they were unplugged it would beep with the engine off but ignition on, this time it only beeps with engine running and not just ignition on.

I will check connections and report back next time i take it out. My battery is also old but alternator puts out 13.8 volts so I would assume it overcoming any battery issues.

 

[alldodge]

My battery is also old but alternator puts out 13.8 volts so I would assume it overcoming any battery issues.

Your bat being old and only getting 13.8V this could be your issue. The alternator should be producing 14.4 to 14.6V once running. Doing only 13.8 your battery may be the issue

 

[QBhoy]

100% agree. Start with battery. My engine the same had loads of random silly codes and then disappeared and sometimes no codes and running rough. Resolved the usual SW press sensor, Diz cap and IAC problems and still on occasion it would randomly beep and leave no code.
The battery was the issue. These MPI felt so heavily on electrical draw. I assumed the same as you with the alternator surely meaning this wouldn’t matter. Totally wrong.
Also worth looking at all the sensor plugs. Just take s a wee drop in that network to throw it all to ****.

 

[nola mike]

. Just take s a wee drop in that network to throw it all to ****.

i love the posts by our UK friends!

 

[Cortes100]

Just a crap shoot ......Another simple thing to check are all the wire connector plugs, (those little snap together things). I had a beep alarm going off but there were no symptoms of a problem. Sort of freaked me out, looked at everything and finally found out it was one of those little plastic connectors. It looked ok, but was not pushed together enough to click into the locked position causing a poor connection. Similar to these;

 

[dubs283]

Definitely check all battery + and - connections at the battery AND the engine

Check the main ground from the engine harness, it should be on the same stud and layered directly to the main battery ground, clean and tight

 

[Searay205]

I checked battery voltage it was 12.6 after sitting for 4 days and Rinda freeze frame data shows 14.6 volts when engine running. My previous information above about 13.8v was incorrect. I was amazed at how clean all my connections were such as PCM, O2 sensors. I did find some white gel type substance on one PCM pin connection. Best I can describe as dried white silicone although that not what it was. I cleaned off the couple pins it was on. Starter connections are very tight and rusted but access is so limited I did not disassemble. Found the ground and it was also very tight with some surface rust. I have to assume unless I want to undertake allot of work and disassemble the connection that the mating surfaces of the starter connection is good as they are very tight. Never has the starter not worked perfectly with zero hesitation. I will spray corrosion X on all the bolted connections (starter, ground) as I did last year.

As far as starter connections they will rust on a Searay 205. Searay installed engine vents on back of boat, when you stop the water splashes over the swim deck and into the vents and back of boat. Very bad design, the vents should have been on the side. I already replaced the carbon steel trim bracket with stainless.

The hunts go on, boat runs perfect. Thanks for all the replies so far.

 

[nola mike]

Guessing that the silicone stuff was dielectric grease intended to prevent corrosion. You should probably replace it, though removing short term won't do anything.

 

[Searay205]

Stuff was way to elastic to be dielectric grease and only 3 out of 20 pins.

 

[danohra]

Did you fix it. I have the same problem