225 sho blowing fuse. help please

[boscoe99]

Boscoe, how about you can you explain how the ETV closes back off when that fuse blows and the ETV motor cannot run it back down to idle ?

I remember having moved an ETV with the key off just to see what it would do. I recall it being spring loaded to the closed position.

Stands to reason IMO that if power were lost to the ETV that the engineers would design it to go to the closed (fail safe) position.

[99yam40]

I remember having moved an ETV with the key off just to see what it would do. I recall it being spring loaded to the closed position.

Stands to reason IMO that if power were lost to the ETV that the engineers would design it to go to the closed (fail safe) position.

if the motor turns it open and closed by changing direction of rotation, how does the spring over come it when it does not move?

does the spring over come the motor and spin it backwards so it closes?

thinking more about it how does it hold the throttle at any position where you want it to stay?
does it keep power on both sides to lock it in place once it reaches the position the con*****er tells it to go?
that would make some sense, because when you loose the fuse you have no power to keep it locked

[rodbolt17]

as a stepper type motor it stays locked in place. don't belive it try to move it with the key on. it is spring loaded and you can manually move it with the key off.
next time you have the key on engine off listen for the ETV whine.
try to find a coby of NEETS resolvers servos and transmitters.
it is all in that book.
you have TR's,TXR's and TX's.

[99yam40]

OK so I get it now

So when 1st key on, I think the ECU sends a signal for the stepper to be at or a little above normal idle position by pulsating the two windings until it aligns with that position
and then holds it there by keeping that winding energized..
when the fuse blows or you turn the key off the spring just beings the throttle back to minimum

Is it possible for the stepper con*****er to energize both of the wingdings at the same time causing excess current draw enough to blow the fuse?

I would not think that would pull enough current to blow the fuse, as it may well be made to have both energized at the same time for a half step.

So now I am out of thoughts on where the problem is if it is not in the relay base,wires, or connectors/terminals.
guess it still could be in the ECU circuity going to ground, but it makes no sense why it goes away right after key 1st on.

[boscoe99]

There have been so many words written that I have lost sight of what the problem is and when it occurs.

[99yam40]

There have been so many words written that I have lost sight of what the problem is and when it occurs.

simply it blows the 10 amp ETV fuse when you 1st power up
but when you power up the motor without the fuse in and install the fuse after, it does not blow the fuse

[boscoe99]

If the wires have all been confirmed to be in good working order, if the fuse block/relay assembly has been confirmed to be in good working order, and the ETV has been removed from the equation but the fuse still blows, then I am speculating that there is a fault within the ECU. No way to inspect the ECU.

What else could it be? Will wait to hear.

[99yam40]

yep, My thoughts too.
hope he finds the problem soon without having too many hours being charged to him for troubleshooting

[HarrisonDawgs]

Those following know the answer already but figured I'd share the results in case it helps the next guy. After codes were checked, ETV isolated, wiring harness checked and all grounds checked good, the ECU was the only thing left. Since there is no way to adequately check the ECU, it was replaced. ETV fuse stopped popping and motor ran as expected for a full day. At the end of that day another problem arose. The starter failed on the last attempt to crank. After another thorough sweep thru the circuitry I discovered the wire to solenoid (brown) was not seated firmly in the connector harness at back of fuse/power block. At this point I am not sure if this existed from the very beginning and contributed to the ECU failure or if was something that occurred after the new ECU was installed. It would be nice to know if this was the culprit from the beginning but fuse block was removed several times (by myself) and have no idea if it were loose from beginning or became loose after reconnecting the harness. At any rate the motor ran fine on the last outing and will be put to a thorough test over the next few days. Thanks for all the help guys!

[99yam40]

I think plugging that connector in and out eventually pushed that connector out .
it should have a tab that locking it into place to keep that from happening, but must have gotten bent.

I see no connection between the start circuit and the ETV fuse/circuit

[boscoe99]

I think plugging that connector in and out eventually pushed that connector out .
it should have a tab that locking it into place to keep that from happening, but must have gotten bent.

I see no connection between the start circuit and the ETV fuse/circuit

I agree. In an SHO the starter circuit is completely isolated from the ECU.

I suspect so much fiddling with the harnesses and such caused a pin to back out of its connector.

Panasonic may be aware of analyses in aviation that show that any time an airplane is serviced/repaired the probability of a forthcoming failure increases immediately thereafter for a period of time.

[panasonic]

I agree. In an SHO the starter circuit is completely isolated from the ECU.

I suspect so much fiddling with the harnesses and such caused a pin to back out of its connector.

Panasonic may be aware of analyses in aviation that show that any time an airplane is serviced/repaired the probability of a forthcoming failure increases immediately thereafter for a period of time.

Yes Panasonic is well aware of that, it's called self induced snags (faults) that occur when any major disassembly has occurred to carry out maintenance. It is a problem all operator's have and must be midigated by extensive testing of effected systems after maintenance. Wiring harnesses are especially affected...many many canon plugs with hundreds of wires attached being unplugged and reconnected can cause many electrical gremlins.

I believe I mentioned this somewhere in this thread about several power heads being removed and replaced. If this is the engine in question.