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Would a faulty power distribution relay cause an ecm on a…

Customer Question
Would a faulty power...

Would a faulty power distribution relay cause an ecm on a 2009 200hp optimax to fail

Mechanic's Assistant: Sometimes things that you think will be really complicated end up being easy to fix. The Marine Mechanic I'm going to connect you with knows all the tricks and shortcuts. Tell me a bit more about what's going on so the Marine Mechanic can help you best.

The power distribution module is making a humming sound intermittently. Would this cause the ecm to fail.

Mechanic's Assistant: Is there anything else the Marine Mechanic should be aware of?

The ground cable was loose. I tightened it, then wen I started the motor the ecm died

Submitted: 4 months ago.Category: Boat
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Answered in 1 minute by:
3/23/2018
Marine Mechanic: Charles, Marine Mechanic replied 4 months ago
Charles
Charles, Marine Mechanic
Category: Boat
Satisfied Customers: 4,888
Experience: US Navy (Ret) Certified Mercury Marine Tech with over a decade of repair experience.
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Hello, my name is***** will assist you.

Are you referring to the main power relay on the engine?

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Customer reply replied 4 months ago
the main power relay is making a humming sound and the marine mechanic is concerned that this may have caused the ECM to fail the humming sound is intermittent
Customer reply replied 4 months ago
I do not want a phone call
Marine Mechanic: Charles, Marine Mechanic replied 4 months ago

With it humming, that would indicate a bad ground going to it, or a weak power supply to it. The relay itself should not be able to take out the ECU.

What is the indication that they are getting telling them that the ECU is bad?

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Customer reply replied 4 months ago
After tightening the ground I started the motor it reved Two 2000 RPM I shut it down the smart craft sensors said faulty position sensor all the temperature sensors had failed and critical low oil in reservoir it was diagnosed that the ECM had failed
Marine Mechanic: Charles, Marine Mechanic replied 4 months ago

To me that sounds like a failed ground circuit, possibly a blown fuse on the 5V reference circuit.

Will the engine start at all anymore?

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Customer reply replied 4 months ago
The ECM unit was replaced the motor starts and runs fine but occasionally the humming returns could this cause another ECM to fail
Marine Mechanic: Charles, Marine Mechanic replied 4 months ago

The main power relay should be replaced if it has not been already. You can swap it with one of the trim relays, they are all the same part number.

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Customer reply replied 4 months ago
the really was replaced but still makes a humming sound occasionally the ground is good power excellent turns motor over and starts up right away what would cause the ECM to fail
Marine Mechanic: Charles, Marine Mechanic replied 4 months ago

A weak ground on the wiring harness, loose battery connections, on a slightly older unit cranking it over with the kill switch tripped would also.

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Customer reply replied 4 months ago
The marine mechanic used to separate key separate battery and connected the motor directly to that and the new really still would make a humming sound we are all scratching our heads there’s only 550 hours on this motor
Marine Mechanic: Charles, Marine Mechanic replied 4 months ago

There are several ground points in the engine harness itself. Look at this pic, see the two ring terminals with the black wires on them. Those are 2 of the grounding points.

https://www.ebay.com/itm/Mercury-Mariner-200-225-HP-Harness-Engine-Wiring-Asy-878082T-8-/292107356143

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