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Battery Voltage and IAT sensor stage 1 and 2

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Hey guys,

Wondering if anybody has any insight on what might be going on with our 2019 malibu wakesetter 24 mxz. We are having a couple problems that started after having it out for a couple outings this year. It has 90 hours on it. Both of the problems I am going to talk about started on the same day so not sure if there is any correlation.

Our one problem is with the batteries. On Saturday, we were running the boat at 11.5 volts and when we turned the stereo on, it dropped down to 10.9 volts and they would go up and down slightly. We checked the batteries and it was showing one of the batteries were bad. We changed them out with two brand new ones and ran the boat today. We were running at 12.0-12.3 volts which is still to low I believe. Again, when we turned the speakers on, the voltage dropped down to 11.8-12.0 volts. I thought maybe an alternator problem but the new batteries were fully charged from when we fired the boat up and connections are all good so I'm not sure.

The second problem is the high air intake temperature sensor is hitting stage 1 and stage 2 (SPN:150 FMI:15 & FMI:0). When we took the boat out again today, we noted a few things. When we aren't moving, the temperature seems to stay low enough but still sat pretty high around 180 degrees. When we were moving slow (5-15 mph), the temperature would rise and set the alarms off. When we would go faster (over 20 mph), the temperature started to climb down and I believe stayed around 170 degrees. So it seems that it only gets to hot when going at an intermediate speed. We also kept the engine compartment open going at that intermediate speed and the temperature still rose to high and set off alarm.

All other temperatures (engine oil, coolant, etc.) are all where they need to be the entire time.

Again, neither of the problems occurred before saturday and they both happened to show up the same day. Not sure if there could be any correlation? Maybe a voltage issue is causing a problem in that sensor?

If anyone's got any idea what might be happening or if this may be a problem you've seen before, anything will help.

Please let me know.

Appreciate any help.



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  • 1 year later...
  • 8 months later...

Brand new 23 MXZ with 7 hours and I just got the engine alarm “IAT sensor high voltage”. Also looking for more information on this topic.  

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1 hour ago, ATXRanchLakeLife said:

Brand new 23 MXZ with 7 hours and I just got the engine alarm “IAT sensor high voltage”. Also looking for more information on this topic.  

Which engine do you have and do you know what SPN FMI fault code occurred?

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