PCM/ECM repair?

nasdaqsam

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I have a 2009 Soutbay pontoon with a 496 HO Mag in it. This past season I ran into an issue with it going into limp mode. I had m mechanic run the codes. It showed a couple sensors bad. We replaced them. Got it back in the water a couple other sensors where showing bad so we changed those. Still the same issue but this time showing all sensors are bad. We have checked all the connections and recommended items we could find online that could be wrong. He does not have the full diagnostic equipment so brought it to the local Mercruiser shop. They state the PCM is bad and needs to eb replaced but where not 100% sure this would fix the issue.

It is looking like I have several options. There is a place online called Sia Electronics that claims they can test it and if repairable will do that for $169. If just tested and bad they ship it back for the cost of shipping. Has anyone heard of or used this company? Are there others I should be contacting?

I could buy a new on a couple grand and hope this is the issue but I am thinking I would rather make sure this is the issue.

Any thoughts on this?

Thanks
 

achris

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Check the 5v and 12v buses from the ecu. Be aware that they have their own 'ground' which is not the engine block...

Chris...
 

alldodge

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Still the same issue but this time showing all sensors are bad.

He does not have the full diagnostic equipment so brought it to the local Mercruiser shop. They state the PCM is bad and needs to eb replaced but where not 100% sure this would fix the issue.

What is the motor serial number?

What is being used to scan for codes and what codes are displayed?

With all sensors showing bad, need to check the 5V side which is feeding the sensors. If one of them is drawing to much current the voltage drops some and then all sensors show failure.
 

nasdaqsam

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Check the 5v and 12v buses from the ecu. Be aware that they have their own 'ground' which is not the engine block...

Chris...

Chris, Thanks for the reply. The boat is put away for winter now we pulled the PCM before we did. The mechanic has confirmed he checked these two buses and found them to be good shape and seated. I will have to call him to be sure he checked the ground also.
 

nasdaqsam

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What is the motor serial number?

What is being used to scan for codes and what codes are displayed?

With all sensors showing bad, need to check the 5V side which is feeding the sensors. If one of them is drawing to much current the voltage drops some and then all sensors show failure.
As stated above the boat is in storage so I do not have the serial numbers. I do not have the exact codes but they showed the following sensors needed to be replaced all at different times. IAC, Idle control valve and tps sensor. It showed a crank sensor code also but that came and went. In the end it showed all sensors bad. I do not know the tester they used but the last one used was by a Mercruiser authorized shop. they checked the connections as well and said it was the PCM. I know that is not much help. As we have the unit out I was thinking of sending it out to either the Sia company or Whipple is saying they can test it all though for more money but on the other hand I could have them put their stage one code in it while it's there.

The only way I may find out if it is really bad would be to have it tested it is looking like.
 
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nasdaqsam

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I did some reading of on line reviews of Sia electronics it is either 5 star or 1 star seems like this one is a crap shoot even at $169. Whipple who has a stellar rep will test for $100, if repairable it will be $600 but while there I could get the Stage 1 for the additional $695. I wish we had the boat in front of us to check it out but I really do not want to waste half the year chasing issues. For the cost all though not cheap I am wondering if it is worth having it checked once and for all.
 

Fun Times

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There is a place online called Sia Electronics that claims they can test it and if repairable will do that for $169. If just tested and bad they ship it back for the cost of shipping. Has anyone heard of or used this company? Are there others I should be contacting?
Any thoughts on this?
Before shipping the PCM to them you may want to call them first as I don't believe they'll be set-up to test or repair your Mercruiser Marine 555 motorola PCM but I could be wrong too.

They seem more fit for the auto industry and Mercury / Mariner is the ford car brand is my thoughts on this one....Sia Electronics = http://siaelec.com/product/mercury-mariner-ecm-ecu-repair-return/


The common marine repair shops for ECM's are linked below for you....Whipple Superchargers does the most with/for the 555 PCM found on the 496's from Mercruiser. Should be about $100.00 to test and $600.00 if they know they can fix it.
https://whipplesuperchargers.com/index.php?dispatch=products.view&product_id=73
http://www.simonperformancetechnology.com/
 

nasdaqsam

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Thanks for the input I was definitely leaning towards Whipple they have such a stellar rep. And for a little more I can get it set for stage 1. Not a big upgrade but not stock either. Thanks again
 

DouglasW

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I am very familiar with the insides of GM automotive ECM's and Chris and Alldodge are right on track. Check the 5v reference voltage output from the ECM. All it takes is one bad sensor to load that down and cause the others to not work. If the 5vdc output is still bad after disconnecting all sensors, then yes the ECM repair shop can fix that relatively easily.
 

nasdaqsam

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I am very familiar with the insides of GM automotive ECM's and Chris and Alldodge are right on track. Check the 5v reference voltage output from the ECM. All it takes is one bad sensor to load that down and cause the others to not work. If the 5vdc output is still bad after disconnecting all sensors, then yes the ECM repair shop can fix that relatively easily.

My options for right now would be to wait and do this which we will when the boat comes of out storage and do nothing with the ECM until we know or send it out to be tested to eliminate it as the possible issue. I am thinking for the $100 to test it is worth the piece of mind. I think either way I wouldn't mind having the Stage1 tune done to it so can kill two birds with one stone. Thank for the input all. We will definitely be going over the connections either way.
 

gm280

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Wow, a simple volt meter and a little time could get this working so quick.

I agree with the above suggestions about the 5 volt reference voltage. All the sensors use that as the reference and the controller response to deviations as feedback from that reference.

If you could check that reference with no sensors connected, it would tell you what is going on. And then connect the sensor will show if it is compromised.

Sending your ECM in for repair would not show any sensor bad, only that the 5 volt reference was good. So even if they check and verify your ECM was operating correctly, you could still have the same problem with a still bad sensor. JMHO
 

nasdaqsam

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Wow, a simple volt meter and a little time could get this working so quick.

I agree with the above suggestions about the 5 volt reference voltage. All the sensors use that as the reference and the controller response to deviations as feedback from that reference.

If you could check that reference with no sensors connected, it would tell you what is going on. And then connect the sensor will show if it is compromised.

Sending your ECM in for repair would not show any sensor bad, only that the 5 volt reference was good. So even if they check and verify your ECM was operating correctly, you could still have the same problem with a still bad sensor. JMHO
Thank you for the input. Either way I have been wanting the Stage 1 upgrade to get rid of some of the soot around the back of the boat. While there we can at least eliminate the computer being the issue. If that is ok when I get the boat out of storage we can start chasing down what else may be causing it. How may sensors are connected to the computer? We have done several all ready. One I know they did not do it the crank sensor.
 

alldodge

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have been wanting the Stage 1 upgrade to get rid of some of the soot around the back of the boat.

This is caused by a rich fuel mix and can be caused by many things, but normally not the PCM. I would check the readings of the MAP first, then move on to other items like, Injectors, fuel pressure, timing, etc.
 

nasdaqsam

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This is caused by a rich fuel mix and can be caused by many things, but normally not the PCM. I would check the readings of the MAP first, then move on to other items like, Injectors, fuel pressure, timing, etc.
I know my mechanic checked the fuel pressure and timing for sure for the sooting. Not sure on the Mapping and injectors. If it is still sooting up when we get it back running to start with, we will check those. Thanks
 

achris

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MAP is Manifold Absolute Pressure, not the mapping... It's a sensor in the intake manifold which the ECU uses to determine load on the engine and, along with other sensors, determines how long to hold the injectors open for... If the MAP is giving false readings the ECU may be sensing a higher load than is there, and injecting more fuel than the cylinder can burn, hence the sooting.

Chris....
 

nasdaqsam

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MAP is Manifold Absolute Pressure, not the mapping... It's a sensor in the intake manifold which the ECU uses to determine load on the engine and, along with other sensors, determines how long to hold the injectors open for... If the MAP is giving false readings the ECU may be sensing a higher load than is there, and injecting more fuel than the cylinder can burn, hence the sooting.

Chris....
Thank you.
 

nasdaqsam

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Quick update. Whipple tested the PCM and found nothing wrong. I held off getting the Stage 1 until we can figure out what is causing the issue since it's not the PCM. When the boat comes out of storage we will have to start checking all the sensors and going through all the advise given here.
 

nasdaqsam

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The computer is finally repaired and the boat running great. So a little info I found out along the way that could help diagnose others boats with similar issues.

I was curious as to what causes these computers to fail. I spoke to the tech at Whipple about it. What happens is when an IAC starts to go they sometimes cause the computer to work extra hard to try and control it. There are two chips in the computer that control the IAC. One is for the IAC itself the other runs the chip that runs the IAC. The chips get sop hot two things tend to happen. The most common is the get hot enough to melt the solder holding them in the other is they over heat and crack around the edges. Either can cause the computer to fail. A tell tail sign is to get into the computer on a clean work bench and slowly turn it over a bead of solder will be in the case. My computer tested perfectly ok on their test equipment and it would even open and close the IAC but it was a weak open and close where it should be a solid noticeable snap. This is why they missed it the first time it did what it was suppose to just not up to spec. And the reason for the soft code on the IAC instead of a hard fault code.

Hopefully this helps others and adds to the mechanics on this forums knowledge base.

Regards
 
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