Mercruiser MPI fault 54 and 56

[QBhoy]

Hi

This looks as if it could be the start of my MPI problems.
As some may know, I recently had a 154 fault. This was the IAC which had no been replaced and was running well.
On Friday night I had a wee full throttle blast. The engine didn't seem to be performing as well as I know it can, with the boat only running about 56 mph gps.
I checked the fault codes on the vessel view and it is displaying a fault code 54 and 56...
From what I understand 54 is a ignition coil fault. Any idea if this is likely to be genuine or perhaps even caused by cheaper ac spark plugs ?
Secondly...what the hell is code 56 ? It isn't listed on any list I've seen.
Does anyone have a specific Mercruiser fault code list ? I think the one I have may be for outboards ? Or is the list generic ?

Thanks
Allan

 

[tpenfield]

Allan,

Sounds like you are heading into the 'MPI meat grinder' with these codes. It was code 152 (not 154) right?

Had you posted the serial number of your engine. I ask because I found a code 54 as an oxygen sensor on a Merc bulletin for an MEFI-3 . . . no mention of a code 56 though. :noidea:

 

[QBhoy]

HI TPenfield

Yeah, you're right of course...fault 152 was the iac.
That's thankfully sorted now with help here.

Serial number is;
OM601937

Thanks

 

[QBhoy]

Screen shot from the vessel view app.

 

[QBhoy]

Knock sensor in there too from previously ! Likely related.

 

[tpenfield]

Service Manual #36 page 2A-40 lists codes 54 and 56 as an ECM to ICM (ignition control module) short circuit. Your engine has the PCM 555 controller (newer than the MEFI's)

 

[Fun Times]

54 and 56 are both EST Shorted....(Electronic Spark Timing): 1-8 Short. Electronic Spark Trigger Signal Circuit 1-8 Is Short.

54 reads EST # 6 is shorted circuit.

56 reads EST # 7 is shorted circuit.

54 & 56 Fault message: Ignition faults. Signal from ECM to ignition driver module shorted. Detectable only at RPM.
Fault Possible root cause: Wiring problem. Coil Problem. May see this fault during overspeed as ignition trigger signal is being turned off.

Fault # 11 reads Knock Sensor # 2....Probably picking up from the two codes above if true.

 

[QBhoy]

Guys

Thanks very much.
Down at the boat just now and the whole thing is playing up....nightmare.
Every time I start the engine there is a new code. The funny thing is that it went fault code 1, then 2, the. 3....and so on. I'm now at 12 (low oil pressure) and I know that isn't genuine. Alarms range from battery hi, low, throttle position...
Must be an electrical gremlin somewhere. Tell me it isn't the ecu?

 

[Fun Times]

Yes sounds like an electrical problem somewhere.

You may want to start by physically checking/cleaning all ground wires/cables... Also make sure your batteries have/are reaching a minimum battery rating of (Non‑DTS models) 750 CCA, 950 MCA, or 180 Ah)
Minimum battery rating
(DTS models) 800 CCA, 1000 MCA, or 190 Ah) With something such as this for example, https://www.harborfreight.com/digital-automotive-battery-analyzer-66892.html

 

[QBhoy]

Thanks fun times. I'm going to start pulling electrical plugs and cleaning tomorrow.
It's just so funny that it is showing faults in numerical order now. Literally every time I start it. Pretty sure it would have ran the full sequence if I let it.
I'm kind of hoping it shows the 54,56 type errors again to give me a starting point with the coil. I think that was genuine because of the power loss.
Local Merc guy is telling me to replace the crap cap and rotor. Not so sure ? Would that cause the whole thing to short out and show such random electrical faults ?
Don't want to just start throwing money at components in a replace and hope for the best effort !
Is this sequence of errors some sort of default thing ?

 

[QBhoy]

https://youtu.be/RG3AtEuzR9Q

Here is a video I've put on YouTube (for the purpose of problem solving) of the exact moment the problem occurred.
Turn volume up and listen for it winding up...then between 40-50 seconds you will hear rpms drop, raise then drop. Hunting. Trim was constant. Didn't notice at the time but very evident in video. Two boats were neck and neck then problem and other flies past.

 

[QBhoy]

Should also mention...gaurdian mode was evident on faults at 90% power at this time.

 

[alldodge]

Have to agree with FT, there is a ground loose somewhere. Could be one which is factory soldered inside the harness, on a terminal lug and it might even be inside the ECM.

I would like to know what the 5V sensor voltage is doing. Each sensor gets 5V on one side and the other goes back to the ECM. So one side should be a steady 5V and the other side should vary. Connect a voltmeter on one of the sensors like the water pressure gauge on the power steering cooler. Note voltage with it ON (no start) and also running. See if it falls below 4.8V or stays steady.

 

[QBhoy]

Thanks everyone.
Alldodge. Just read your post properly. Just in form the boat 2 minutes ago.
That's a good call with the sensor voltage. I'll pull a few connections tomorrow and test the voltage.
As suspected...tonight at the 13th time of starting since the initial fault, I got error code 13. I'm certain on the 14th time starting it...it will show error code 14.
It's certainly in gaurdian mode and limiting the rpms. I was running light this evening and flat calm and only achieved 4400 rpm or just over and about 52mph.

 

[QBhoy]

Apologies. The fault codes screen shot was from the original post. Here is a recent one.

 

[QBhoy]

One of the constants seems to be the "SW pressure low" error. Or fault code 3 ? That has registered twice tonight.

 

[QBhoy]

Latest update...so confused...
So I was out last night with a few guys from work. Was going to just take it easy (they had never been on a quick boat before) but then they asked how fast she would go.
Explained that normally she would be running 60+ or more lightly loaded, trimmed up and the big un aerodynamic hood off her.
They egged me on so I opened her up....
With 4 people on board I knew she wouldn't perform very well, but went for it none the less. I thought I would just give them a bit of drama with the corsa exhausts open and that would do.
I opened her up and trimmed up to let one of them video the rooster tail. All good, then I looked at the rpm on the vessel view and she managed 4800 rpm !! What the hell is going on ?
Throwing a rooster tail is not the fastest way to go, but surely if she is running in gaurdian mode, she shouldn't pass by a certain rpm (4400-4500).
Normally she would hit the rev limiter if I trimmed up as high, so still not performing as she should and only hit 57mph gps....but I'm still confused !
A friend of mine is a pretty good auto mechanic...he is convinced it's a shorting or earth problem.
Really need some help here.

 

[QBhoy]

Surely it can't be the vessel view mobile Bluetooth device ? This is plugged into the smart craft diagnostic port ? Direct link to the ECM ? Can this have a bug ?

 

[alldodge]

Surely it can't be the vessel view mobile Bluetooth device ? This is plugged into the smart craft diagnostic port ? Direct link to the ECM ? Can this have a bug ?

At this point anything is possible I don't know where else to look. I would call Merc Tech support, but being over in Scotland don't know if that's possible

 

[QBhoy]

Today...
I changed the crap cap and rotor. Had a wee test run on the Loch. The weather was fowl with strong winds and a fair chop and two on board.
The boat certainly performed better than recently. Even managed 4600rpm odd (150-200 up on recently) and a few extra mph.
Still showing fault codes on vessel view. Fault 3 is common to every start now. Think that is the SW pressure switch ?
Certainly better, but perhaps not perfect. Hard to tell with the hood up though and really windy. The boats speedo was over 60mph for the first time in ages and gps was around 56/57. Better than recent times but not sure it's perfect. Does the SW low pressure alarm still throw up gaurdian mode ?
Hopefully the weather clears soon and I can get the hood off it soon.