Mercruiser 3.0 PCM-09 Code 3050

jnelsonusmc

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Pre O2 and post O2 readings are the same.

With having both O2 sensors replaced recently my wag is the catalyst has failed. Without the catalyst the pre/post O2 numbers would be the same, like your situation.

Time to check your catalyst
I am leaning that way but need to make sure before spending that much for a new catalyst. Do you know of any specfic test I can run to make sure its a bad catalyst. I have read several articles that list that as a common issue with this engine. Thank you for your reply.
 

jnelsonusmc

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Your Long Term fuel trim is way too high according to the data. The ECM thinks it sees a lean condition due to the upstream O2 sensor reading so it's throwing more fuel at it. But the data is showing a negative oxygen value......odd. I would do an injector cutout test using the Diacom tool to see if you can identify the misfiring cylinder due to injector issues.

I would also want to look at the upstream O2 sensor voltage to see if the sensor is seeing a switching rich/lean condition when in closed loop.

Have you checked your spark plugs?

A lot of conflicting data here, in my humble opinion.
Brand new spark plugs - timing is spot on no noticeable timing misses while running.
 

jnelsonusmc

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Guess @muc must be tied up, he normally comes along to help

It's like your not getting any response from the sensors to the PCM (bad or broken connection). Yes their should be a difference between O2 going in and O2 coming out. Don't understand the No exhaust Temp, guess the sensor isn't there?

Looking at motor on line I'm seeing 7 different Manuals and all show different serial number breaks for the EC. There has been several part number changes for the motor which could mean it doesn't have the sensor
I did not notice an exhaust temp sensor - I will check more closely tomorrow and report back. Also will pull the O2 sensors and check voltage. Thank you for the reply.
 

mvn

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Have a look at this document.....page 161 to 164. The voltages I'm referring to correspond to the figures on those pages.

Mark
 

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jnelsonusmc

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I figured out what I was doing wrong with the Diacom diagnostic program.
Attached is the running report I pulled this afternoon. It shows alot more data points and the O2 sensors are reading correctly it looks like.
 

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mvn

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Fuel trim @ -3.6% looks good. I don't know if this is short term or long term but good nonetheless. Misfire counts are perfect. Now that you can generate what looks like a valid report, I assume you'll capture data when under load.

Mark
 

muc

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The report you posted looks ok because you’re not running the engine at the speed and load required to get the catalyst monitor running.

VERY IMPORTANT!!!!!!!!

Need to run the engine under load at 1800-3000 rpm. You want to keep the throttle setting constant while running.


Code SPN 521009 FMI 31 means the engine has gone into Guardian, will need to look at fault freeze frame to see what caused this code.

Code SPN 3050 FMI 1 means the Catalyst has failed its OSC (oxygen storage capacity) test, you will need watch what’s happening in the O2 monitor section. Your engine needs to see at least 150mg of OSC. What number do you see?

This engine should have thrown other codes before it got to the point of the 3050/1

Makes me think someone might have removed the catalyst.
 

muc

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Noticed earlier that someone recommended running a injector kill test. I wouldn't recommend running this test on a EC engine without proper training ---- can cause some pretty good damage in a hurry!
Same goes for spark kill test.
 

mvn

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Noticed earlier that someone recommended running a injector kill test. I wouldn't recommend running this test on a EC engine without proper training ---- can cause some pretty good damage in a hurry!
Same goes for spark kill test.
That was me. That was the only way I was able to determine I had a dead cylinder. The fuel trim was pegged at max although I was able to run the test at idle and not under load. What damage could be done?

Mark
 

jnelsonusmc

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Noticed earlier that someone recommended running a injector kill test. I wouldn't recommend running this test on a EC engine without proper training ---- can cause some pretty good damage in a hurry!
Same goes for spark kill test.
Understood, thank you for the heads up, will follow your recommendation.
 

jnelsonusmc

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The report you posted looks ok because you’re not running the engine at the speed and load required to get the catalyst monitor running.

VERY IMPORTANT!!!!!!!!

Need to run the engine under load at 1800-3000 rpm. You want to keep the throttle setting constant while running.


Code SPN 521009 FMI 31 means the engine has gone into Guardian, will need to look at fault freeze frame to see what caused this code.

Code SPN 3050 FMI 1 means the Catalyst has failed its OSC (oxygen storage capacity) test, you will need watch what’s happening in the O2 monitor section. Your engine needs to see at least 150mg of OSC. What number do you see?

This engine should have thrown other codes before it got to the point of the 3050/1

Makes me think someone might have removed the catalyst.
Thank you for all the guidance on this I have attached the freeze frame listing of all history for faults thrown. Looks like the Exhaust Manifold Overtemp is what threw the engine in Guardian Mode on me. The shift fault was all me, the coolant overtemp fault I replaced the thermostat - it was in bad shape and missing the insert that holds the thermostat in place. The TPS fault was fixed with new TPS installed the O2Control fault was fixed with new O2 sensors.
 

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jnelsonusmc

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The report you posted looks ok because you’re not running the engine at the speed and load required to get the catalyst monitor running.

VERY IMPORTANT!!!!!!!!

Need to run the engine under load at 1800-3000 rpm. You want to keep the throttle setting constant while running.


Code SPN 521009 FMI 31 means the engine has gone into Guardian, will need to look at fault freeze frame to see what caused this code.

Code SPN 3050 FMI 1 means the Catalyst has failed its OSC (oxygen storage capacity) test, you will need watch what’s happening in the O2 monitor section. Your engine needs to see at least 150mg of OSC. What number do you see?

This engine should have thrown other codes before it got to the point of the 3050/1

Makes me think someone might have removed the catalyst.
Thank you again Muc for all your advice, I have a Ham radio event this weekend so it will be a few days before I can get on the water and do a load test on this. Going to check to see if the catalyst was removed tomorrow and post back to you. If so load test not really needed... thanks again for all your help.
 

jnelsonusmc

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Thank you for all the guidance on this I have attached the freeze frame listing of all history for faults thrown. Looks like the Exhaust Manifold Overtemp is what threw the engine in Guardian Mode on me. The shift fault was all me, the coolant overtemp fault I replaced the thermostat - it was in bad shape and missing the insert that holds the thermostat in place. The TPS fault was fixed with new TPS installed the O2Control fault was fixed with new O2 sensors.
Muc - OCS Raw Port and OCS Raw Stbd showing 0.00 mg last time I ran the engine
 

muc

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That was me. That was the only way I was able to determine I had a dead cylinder. The fuel trim was pegged at max although I was able to run the test at idle and not under load. What damage could be done?

Mark
That was me. That was the only way I was able to determine I had a dead cylinder. The fuel trim was pegged at max although I was able to run the test at idle and not under load. What damage could be done?

Mark
We were told in school that you can flood the cat with unburnt fuel or too much oxygen. This is dependent on RPM, load and amount of time doing the test. What engine you’re testing will need to be considered also because of the amount of catalyst material present. 3.0 has one cat, 8.2 has 3 per side, so there is a big difference when dropping one cylinder.

I have been somewhat reluctant to comment on this post because I have never worked on a 3.0 EC engine (no dealer I have worked for would ever sell this package) and I’ve never used Diacom on a MerCruiser EC engine. So please take my comments with a grain of salt.
 

muc

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Thank you again Muc for all your advice, I have a Ham radio event this weekend so it will be a few days before I can get on the water and do a load test on this. Going to check to see if the catalyst was removed tomorrow and post back to you. If so load test not really needed... thanks again for all your help.
Unless you have seen good catalysts vs bad cats, it might be a good idea to post some pics of what you find. You need to look at both ends, different faults can burn one end or the other and sometimes both.
 

Fun Times

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Looks like the Exhaust Manifold Overtemp is what threw the engine in Guardian Mode on me.... the coolant overtemp fault I replaced the thermostat - it was in bad shape and missing the insert that holds the thermostat in place... the O2Control fault was fixed with new O2 sensors.
I have been somewhat reluctant to comment on this post because I have never worked on a 3.0 EC engine (no dealer I have worked for would ever sell this package) and I’ve never used Diacom on a MerCruiser EC engine. So please take my comments with a grain of salt.
Pretty much the same thing here Muc but non the less thanks for yours and all the others insight in here because together we learn as that is what these forums are all about. :)

That mentioned, I'm not totally sure myself but worth putting out there to converse...'Would you or anyone here think maybe with the thermostat internals disintegrating like mentioned could flow towards the catalysts causing blockage or damage in that area causing this issue?

Seems either way the catalyst housing needs opened up for inspection.
 
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