2 beeps each minute

[achris]

Hi All.

Out diving today. Running between locations, engine hadn't had any problems, oil and water good, drive oil good. Running about 3200rpm, had been for about 25 minutes, then had the engine alarm started beeping twice every minute. No noticeable power loss, idle was a bit slow and unsteady (when I pulled back), but no stalling. Took it up to 4300rpm, solid alarm tone. Pulled back to 3200 and ran home without further incident, apart from the 2 beeps each minute.

Got home, put the laptop diagnostics on, no codes. Suspecting the IAC, pull it and found it jammed shut. Played with it a little bit and got it free and re-installed it. Ran the engine up on the flushers, same thing, 2 beeps each minute. Put the diagnostics on and now it's throwing a 'IAC Output' code and the ECU has set engine power to 90%. Engine was idling perfectly, and when I unplugged the IAC, no change... ???

All other sensors ready good. I metered the IAC and it shows about 0.9Ω. And that was also metering from the pins on the ECU connector. (Plug A, pins 20 and 23)... (To check the wires themselves.)

IAC Output... Is this the ECU saying the output TO the IAC is faulty (ie, and internal ECU fault) or is the ECU measuring the current flow through the IAC and reporting that the IAC is not working?

Thanks for any help....

Chris......
Actually it wasn't a good day mechanically. The car sheared an alternator mounting bolt (remove the alternator belt to get home), and the one-way clutch bearing in the Powerwinch collapsed too... :facepalm: But we did get 10 lobsters, and some nice fish...

 

[banshee owner]

Re: 2 beeps each minute

im a automotive mechanic by trade. i have never dealt with marine inboard or codes they kick up but iac and all that jazz is right up my alley. Do you have a specific code number and with your laptop can you see a data stream from the ecu or just pull codes.

Alot of times the ecu will kick an iac code when it cant control the idle whether it be because of a faulty iac or another bad sensor or intake leak etc. basically you have to be careful with iac codes if you have a bad enough intake leak and the computer cant command the iac to bring down or bump up the idle then it thinks there's a problem with the iac and may in fact set a false code. what engine is in the boat. ill be at work today and if you have an engine i maybe able to give you a direction of diagnostic as what the code is doing.

 

[achris]

Re: 2 beeps each minute

im a automotive mechanic by trade. i have never dealt with marine inboard or codes they kick up but iac and all that jazz is right up my alley. Do you have a specific code number and with your laptop can you see a data stream from the ecu or just pull codes.

The software for Mercruisers is not anything like automotive software. No numbers and no data streams, just the fault code, "IAC Output"... I do get a reading of the duty cycle on the operations page... It was reading 30% at idle and about 50% as the revs climbed...

Alot of times the ecu will kick an iac code when it cant control the idle whether it be because of a faulty iac or another bad sensor or intake leak etc. basically you have to be careful with iac codes if you have a bad enough intake leak and the computer cant command the iac to bring down or bump up the idle then it thinks there's a problem with the iac and may in fact set a false code. what engine is in the boat. ill be at work today and if you have an engine i maybe able to give you a direction of diagnostic as what the code is doing.

As always, in the signature... (4.3MPI, uses a standard BWD 50558 IAC)

Having never played with an IAC, I had a play with it with a screwdriver. It seemed to be jammed. I was then able to get it to move like a solenoid by sliding the cup shaped stopper up the shaft a little, then the shaft moved in and out of the 'coil'? ....

Have I killed the IAC (completely), or is that how they should work?

Thanks for your help...

Chris...

 

[achris]

Re: 2 beeps each minute

Think I may have found my answer...

Boatinfo - Mercruiser Service Manual nr. 36 - 2001-Up - ECM 555 Diagnostics

About halfway down....

A malfunction of the IAC will set a fault of 'IAC Output'.

Price of one of those little nasties in Australia... $220 :faint2:

Cheers all.

Chris.......
(should have looked in the book first, ah... :facepalm

 

[alldodge]

Re: 2 beeps each minute

You said your engine is idling normally which will tell me it's not your IAC. Starting to sound more like the seawater psi low. I would suggest resetting the IAC and put a meter on the seawater pressure switch

Two Alarm beeps every 60 seconds are for:
1.) Faulty cam,
2.) IAC,
3.) MAP,
4.) MAT,
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
12.) Dirty IAC muffler

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 loses it's ground it could sound the alarm. As an additional test, try adding a ground wire to the sensor threads to stop the horn.

 

[achris]

Re: 2 beeps each minute

You said your engine is idling normally which will tell me it's not your IAC. Starting to sound more like the seawater psi low. I would suggest resetting the IAC and put a meter on the seawater pressure switch

Two Alarm beeps every 60 seconds are for:
1.) Faulty cam,
2.) IAC,
3.) MAP,
4.) MAT,
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
12.) Dirty IAC muffler

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 loses it's ground it could sound the alarm. As an additional test, try adding a ground wire to the sensor threads to stop the horn.

Hi AD,

So, I have the vehicle fixed (that was first priority).

One of the first things I thought it could be was the water pressure sensor, but that's showing fine in (live) diagnostics. I pulled the IAC off and ran the diagnostics on it using IAC function test. Basically cycles it from +100% to -100%... The IAC didn't move. The next step I'm going to try is putting an oscilloscope on the ECU outputs. Just make sure the IAC is being commanded.

I just wish I had one spare... Just pull it in and I would KNOW for sure... :facepalm: I guess it's my fault for living in such a non-competitive country. :noidea: If I had something like an O'Reilly's round the corner, I'd just go and get one... Oh, well....

As for the engine idling 'normally'... It was running at the right speed, but did sound 'off' a little. It was only when I checked the off-line diagnostic readout I noticed the ignition timing was -9 degrees. I now suspect the ECU was backing the timing off to keep the speed down... Clever little ECU, ah?

Chris...

 

[achris]

Re: 2 beeps each minute

Well, just ran it again, this time with an oscilloscope on the output of the ECU for the IAC... IAC is being commanded, but not moving... Conclusion... IAC faulty... Now just to wait for the pony express to swim the Pacific....

Chris.....

 

[Fun Times]

Re: 2 beeps each minute

Sorry Chris that I didn't get a chance to chime in earlier to let you know that it sounds like you may have a faulty IAC valve before going through all the testing procedures that I probably would have said you needed to do anyways.

Doubtful it would have been the PCM on your engine model. But had it been, there are a couple of places over here in CA that may have been able to repair it vs looking for a new one.

Hopefully you ordered an IAC muffler as well?

 

[achris]

Re: 2 beeps each minute

Hopefully you ordered an IAC muffler as well?

I put a new muffler in about a year ago (and still have a spare on the shelf)... Looks like the IAC was jammed, so I'll be implementing a cleaning schedule for it in the future...

Update: Pulled the IAC off and apart, just to see how these things are constructed... Looks pretty simple, just a solenoid. With all the works removed and just the coil and the plunger in place I flicked 12v onto it... Nothing, narda, nil, not a sausage.... I think the coil is shorted internally. I get a spark, but no movement of the plunger.... I have also found that this particular IAC is common to most of the Mercruiser MPIs (part# -862998)... and it's from..... A Ford 3.8L V6 engine... Here's all the different part numbers and places I have found it at...

Summit Racing
O'Reilly's
Autozone
Car Parts Discount
And basically any Ford dealer!

Part numbers:-
Standard Motor Products AC423
BWD50558
Hitachi ABV0006

Hope this helps someone in the future....

 

[alldodge]

Re: 2 beeps each minute

Good to know you have it figured out. Gee wiz 220 for a 55 part, talk about import fee's.