Mercruiser 5.0 MPI - Shift Position Sensor Error

[jernberg]

Hi
Im having trouble with one of my 5.0 MPI engines from 2003.

At around 3600rpm I get the two beeps per minute error. I have hocked up ScanTool to see that I get an error with the Shift Position Sensor. The error also puts the engine into guardian mode with 89% power.

Have tried this multiple times and the error always occur around 3600 rpm. Switched the sensor with the other engine with the same result... All looks good when I shift gear at idle.

For me it seems like something else is triggering this error, what could it be?

Below also the values from the Scantool session for both engines. Its the BB engine that is giving me trouble.

Thankful for all help I can get as Im stuck...

Best
/Henrik

 

[jernberg]

Nobody that have had this fault? Struggling with what to do next. Could it be the ECM...

/Henrik

 

[Fun Times]

Try connecting the scan tool with the engine running, go to live data, then shift the shifter and see if it goes from neutral to in gear and back out of gear a few times... Also try pushing the shift switch button in & out with a small tool to see if it will change state.

If it don't change then using a multimeter, ohms check the switch while pushing the button then ohms check the MPI wiring harness from the ECM to the shifter switch connector.

If all the ohms checking checks out okay except the scan tool won't change state then send the ECM out for inspection as swapping ECM's with a unidentified failed component or wire could be disastrous at times.

Good luck.

 

[jernberg]

Hi
Have done test with ScanTool connected, shift in and out of gear and all seems normal. Took out the sensor and pushed the "button" all seems fine. Also switched the sensor with my other engine. Same result, it gets in neutral at around 3600 rpms...

Have not ohm checked it as for me it dosent seem like the switch is the problem. Do you know what the ohm reading suppose to be?
Also feels far fetched that another system would use this error to get the engine into guardian state?

Thinking about swapping ECM between the engines just to rule that out.

/Henrik

 

[Fun Times]

Hi
Have done test with ScanTool connected, shift in and out of gear and all seems normal. Took out the sensor and pushed the "button" all seems fine. Also switched the sensor with my other engine. Same result, it gets in neutral at around 3600 rpms...

Have not ohm checked it as for me it dosent seem like the switch is the problem. Do you know what the ohm reading suppose to be?
Also feels far fetched that another system would use this error to get the engine into guardian state?

Thinking about swapping ECM between the engines just to rule that out.

/Henrik

When testing the switch in question with a meter you should see a reading of nothing (< zero, infinity, 0.L) to something as its an open and closed switch that's normally closed at rest. Mercruiser didn't publish any numbers.
http://www.boatinfo.no/lib/mercruiser/manuals/mercruiser36.html#/96

No matter what other problems there may or may not be in your case, the neutral reading while in gear is of the biggest concern as the neutral rev limiter guardian system will not allow you to rev past 3500 - 3800 RPM range while in "neutral" + it will sound the warning horn.

?, So while in gear either/both in and out of the water and you are advancing the throttle while watching the scan tool, can you watch the gear indicator live data switch from in gear to neutral at or before getting to 3600 RPM?

You could also have a misadjusted shift cable or loose/failing shift plate assembly......Or a vibration to one of the wires between the switch and ECM. Carefully wiggling, pushing in the wires while watching the scan tool may help locate a problem.

For ECM repair, see the following link. https://whipplesuperchargers.com/index.php?dispatch=categories.view&category_id=170 $100.00 to test/diagnose $500.00 to repair if it's possible.

 

[jernberg]

Hi
Thanks for the reply. I will do more tests. But when I had the ScanTool connected I watched the live data and couldn't get this error until I hit aprox 3600rpms.

Best
/Henrik

 

[Fun Times]

Hi
Thanks for the reply. I will do more tests. But when I had the ScanTool connected I watched the live data and couldn't get this error until I hit aprox 3600rpms.

Best
/Henrik

That would be unusual so as you near the RPM range also watch the switch and linkage for vibration/movement....Let us know what you find.

 

[jernberg]

Hi
Is something special happening in that rage (3600)? Sensor and ECM wise?

/Henrik

 

[Bt Doctur]

http://media.channelblade.com/EProWebsiteMedia/3506/Mercruiser warning horns.pdf

 

[jernberg]

Hi
Did som digging around and it seems like the "guardian mode" for this sensor knocks in at 3500 rpms. So maybe it is a wiring problem after all as I already tried switching the sensor with the "good" engine with the same result.

Best
/Henrik

 

[Fun Times]

Hi
Is something special happening in that rage (3600)? Sensor and ECM wise?

/Henrik

I think you got it with your last post but yes, if you're trying to go past the max allowed RPM range while the ECM thinks the engine is in neutral then the rev limiter is going to kick in...Same thing/concept on later model cars and trucks. You have to find out when it changes state and why at that RPM. Wiggle some wires and shift cables. Could it be a bad ECM? Though very rare for a problem like this, yes it could. Good Luck.

 

[Bt Doctur]

if its DTS, there was a recall
Due to defects in the potentiometers of the electronic remote control (ERC), a single trace
lever fault alarm can occur which will create an audible six second alarm tone and generate
a fault pop‑up on the VesselView screen or SmartCraft instrument, if so equipped. When
this fault mode occurs, the Guardian strategy will limit throttle to 65% of available power
and the shift position will remain in the gear location the engine was in when the fault was
triggered
The shift function will not be available when called for by the ERC when the above fault
occurs and Guardian is active on command module software versions 75 and earlier. This
issue has been reported on early usage, low hour applications, but may occur at other
times.
The new software version 76 (P/N 891661R10) will limit throttle to 65% of available power
and the shift demand will remain active allowing shifting of the engine, even when the lever
fault is triggered.
The system can be reset to enable shifting by one of the following procedures:
For all DTS boat configurations:
• To clear the fault and reinstate shifting, if safe to do so, shut engine or engines off for

 

[Bt Doctur]

Bulletin No. 2008-06
OEM No. 2008-05

 

[jernberg]

Hi Bt Doctur
I dont have the DTS system just regular drive by wire.

Thanks
/Henrik

 

[jernberg]

Hi all
Problem solved today!

It was as easy as there was some wiggle room gear shift plate. When I just switched gear the sensor worked great but when i pressed the wire by hand it could go a bit further and the sensor "button" fell of its place. Imagine this could have happend going up in plane and the ECM got the error code. Thightend the wires a bit and the problem was solved.

Dont understand why they have made the area where the sensor "button" is being pressed down so small. There is not much room for error.

Thanks for all help!
/Henrik

 

[Fun Times]

Good to hear you were able to locate and repair the problem easily for you......With your description, It's kind of hard to get a visual of the area that you had to "repair". Was it the switch wire/s or engine harness/connector wires....Only asking due to you mentioned you tried another switch at one point. Maybe a photo of the problem area will help others someday.

 

[jernberg]

Hi
Here´s an image that shows the sensor and the shift plate. In the shot the shift is in forward gear.
As you can see the sensor is very close to the edge and with a bit slack in the wire the sensor moves out of the area where the "button" is pressed in and the ECM will think you are in neutral.

Best
/Henrik

 

[Tim Serbst]

Hi
Here´s an image that shows the sensor and the shift plate. In the shot the shift is in forward gear.
As you can see the sensor is very close to the edge and with a bit slack in the wire the sensor moves out of the area where the "button" is pressed in and the ECM will think you are in neutral.

Best
/Henrik

Can’t seem to get picture of where sensor switch