Smart Craft troubleshooting

[imported_Blueskies]

Just bought a 2001 boat with twin 200's and the three guage Smart Craft system. I'm new to Mercs and still trying to learn their habits.
Every time I turn the batt switches on and start the engines I get a "Sensor Fault" msg on the port tach which then flashes to "Limp home Throttle" If I press the (mode) key the msg clears. The throttle response is normal and all temps and pressures read normal as you scroll thru with the "mode" key. The msg does not appear on any subsequent starts until I turn the batt switch off again. I have read thru the manual and cannot find this particular code in the Info or Troubleshooting section -

Is there an internal battery in the guages that needs to be replaced periodically??

Many thanks for your help.

 

[Silvertip]

Re: Smart Craft troubleshooting

First be aware I'm familiar with this system from a conceptual perspective only. So -- I would not expect to find a battery in the gauge since fault codes are probably generated by software in the ECU on the engine. What may be happening is there is a power on issue with the ECU on that engine. ECU's generally have a "keep alive" circuit that draws a small amount of current, or they may use NVRAM to hold any fault codes or other operating parameters. If the ECU uses a keep alive function, that circuit goes dead when the battery switch is off. If using NVRAM, the spike when the battery is switched on may be triggering a fault code in that ECU. That doesn't account for why the other engine doesn't behave the same way which is why I suspect a glitch in the affected ECU. Depending on how much work it is and how handy you are, you could switch ECUs and see if the problem follows. If it does, its an ECU issue. If not, its probably a gauge problem.