ECM 555 Question

I have a set of 2003 mercruiser 350 MPI with serial numbers 0M317080 and 0M317081. They both have the motorola ECM 555's. I purchased a Rinda scan tool with the 4 pin connector. Went to check the engines out (no issues just wanted to see the info in the ECM) and when I plug in the connector, I get nothing on the display. I am almost sure that I need 12 VDC on the two outer pins that the scan tool hooks up to so I checked with my multimeter and am only getting 5 VDC. Both engines are the same. Any idea why I am not getting the proper voltage. The engines work fine with no issues. Any help would be appriciated. Steve

Re: ECM 555 Question

Did you turn the ignition key to on? Did the dash gauges work normal with key on?

Re: ECM 555 Question

Yes and yes. From my understanding the two outer pins should have 12 vdc with ignition on or off. Either way, I do not have 12vdc with the ignition off, ignition on or with engines running. The terminal points for this voltage are 102 and 104 on this model year from the manual. I do not see any fuses inline. I have both the engine and ECM manual so I guess I am going to track down pins to see if I can find the issue. It's kinda wierd that both engines are doing the same thing. As I said in my post, I have zero issues with the engines. Any ECM 555 experts out there??? Steve

Re: ECM 555 Question

Not sure you'd call me an expert, but I have a V6 MPI with the same ECU (different programming obviously) and I also have the Rinda diagnostic software.. Does also being an electronics tech count?

Are you running the software on a laptop or is it a scan tool? I have the laptop software and have no issues, it runs nicely... Are you measuring the voltage on the diagnostic connector on the engine with the tool removed? I just went and checked mine... A prefect 12 volts between the 2 end pins when the key is ON.... If it was only on one of your engines I'd say a bad splice, but both? Seriously doubt that!!!

Chris.......

I guess this is what you're talking about....

Re: ECM 555 Question

Yes this is the same drawing I am using from service manual 36. I have 5 volts accross these terminals on both engines. I will have to start to track down the wires and see what the issue is. My guess is a ground somewhere. And yes it is strange that both engines show the same isssue. I am attempting to use the scan tool and not software. Steve

Re: ECM 555 Question

Ground problem would be my guess too... Try metering from the 'ground' pin to the engine block.. If that shows 0 volts the problem is the power side of things... If you get a voltage around 7 volts (I suspect you will) then the problem is in the ground circuit... Maybe a ground wire not connected correctly...

Chris.....