2002 johnson 50hp intermittent rough running lacking power and check engine light

jakedaawg

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Do not probe the ecm with an ohm meter. These tests are performed on the harness/es to test the various sensors attached.
 

OttawaPhil

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That's great! So those three sensors are the ones that tell it to fire?
I have the same manual as you arriving today.
Hopefully I will get it sorted tonight.
I also have a DVA adapter for my voltmeter to diagnose it.
 

jakedaawg

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So those three sensors are the ones that tell it to fire?

Kind of, the ckp sensor/s send a pulse to the ecm which uses that and voltage from the map sensor and other pulses from the cmp sensor to fire the coil at the proper degree of engine rotation.

If I recall you swapped the coil for a different cylinder and the issue stayed at #1 which means the coil is probably good assuming there is good wire to the coil. I believe you checked that also.

That leads us to needing to check the ckp sensor for the #1 cylinder. This is the only other cylinder independant thing. The map and cmp sensors are working because you have a working #2 and #3.

The ecm would be the final thing but I will not reccomend that to be bought over the nets. I believe its dealer only anyways...

Again this all assumes you checked for spark with a good test and that the timing is correct. Harder to check timing without cylinder #1.
 

jakedaawg

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It would be nice if you had a buddy with the same motor close by...just plug your ecm into his motor...
 

OttawaPhil

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No buddies with the same one.
and another problem my ECu is only one plug not a bunch like in the manual. Wire colors look different too 8-(
anyone have a pin out for ECU with just one large plug for 2003 johnson 50hp j50pl4st ?
thanks!
 

OttawaPhil

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No buddies with the same one.
and another problem my ECu is only one plug not a bunch like in the manual. Wire colors look different too 8-(
anyone have a pin out for ECU with just one large plug for 2003 johnson 50hp j50pl4st ?
thanks!
 

OttawaPhil

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Also it does not seem to have the ckp three sensors. Do I have the wrong manual?
 

OttawaPhil

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Here is what my connector and manual looks like
 

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OttawaPhil

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And I do not seem to have the three part ckp sensor though not sure don't have flywheel puller.
I should be able to see the ckp sensors without pulling it right?
 

OttawaPhil

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This is where they go right? I have nothing there.
seems to be only one sensor on the right of the pic.
what does this mean? How to I test one sensor for three plugs?
 

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OttawaPhil

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I have confirmed its the wrong manual. I have the three spots on the block for the sensors but they're not there.
confirmed this pic from the manual shows where they are and i don't have them. That sucks this manual was expensive
any ideas where I can get the right procedure to troubleshoot?
 

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OttawaPhil

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Found the addendum here is what mine looks like
 

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OttawaPhil

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But not sure how to test the number one sensor when there is only one sensor? And the wire colors and pins and plugsmare different.
 

jakedaawg

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I'll look at a 04 model manual in the morning...I am out to dinner and away from the shop right now. I have not seen one like that that I can recall. They dont have issues very often...
 

jakedaawg

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Sorry Phil, got super busy today and forgot all about it. I have now set a reminder on my phone and will look tomorrow.
 

jakedaawg

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In a nutshell...

you will need an "sr" manual. That's the 2004 manual.

From personal experience you will also need a 44 pin breakout box. That allows you to check that big harness and related sensors. If my memory serves me there was no reliable way to "back probe" to get reliable readings. That tools runs several hundred dollars.

I think to correctly diagnose this you will also need access to the 4 stroke diagnostic software...

it may end up being less money to haul the boat the 6 hours...should you choose to make sure they have a tech that actually knows these engines...not all shops are expert in all motors. I know we certainly were not.

hope that helped, feel free to ask for more if that did not cover it...
 
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