Limp Mode Reset

[Quitsa]

Tuesday I ran out 90 miles to fish offshore and when we slowed back to idle to set up for fishing, my port engine alarmed with a fault showing “accelerator pedal or throttle low voltage” (SMX displays) and would not go above idle of 650 rpms. I have dual station Twin Disc EC300 controls. The problem affected both stations and it did not matter if the engines were operating in synchronized mode or with independent throttles. The gear shifted normally in and out of neutral.

Needless to say, this ruined our day since we had the prospect of a 12 hour return home effectively on one engine instead of a 3 hour trip.

I tried cleaning the connector at the throttle lever with contact cleaner to no avail. Then entirely on intuition, I shut down the affected engine for 90 minutes as we steamed home and then tried again. Miraculously, the engine spun up so I immediately got going at cruise speed and of course did not dare touch the levers again until outside the harbor entrance. The engine display no longer showed the alarm or fault code (which don’t seem to be stored).

The consensus from my mechanic and the Twin Disc rep is that the voltage sense cable from the EC300 to the engine has an intermittent fault that “fixed itself” or that perhaps my effort to clean the connectors fixed the problem. I ran the boat again yesterday for an hour or so staying close to home and everything works fine.

My question is how does the “limp mode” work? Shutting down the engine for a minute or two did not reset it even though the problem had apparently gone away. When I looked at the troubleshooting information for this fault code on the Cummins Quickserve website, the procedure calls for resetting with the Insite software tool. Is there a way to force a reset without Insite? Obviously my engine did reset itself but it sure would be nice to know for future reference whether there is a procedure or what the shut down time interval has to be. Thanks.

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[Corey Schmidt]

The only input I can provide is that if the engine sees a throttle voltage signal outside of the expected range, it will DE-RATE…. meaning the at the engine computer (ECM) thinks something is messed up with the throttle input signal and will de-rate the engines performance until the issue is fixed… my assumption is that this is 100% a safety issue….

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