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  1. #1

    03 MSX 140 fault codes

    I've got my reed valve problem fixed and the motor now runs on all three cylinders so I took it to the lake yesterday and it initially started out okay but in a short time it started with a high-end miss, flashing the check engine light and over temperature light. I brought it back to my shop and pulled the codes and I'm getting 43 41 47 and 48. I have a service manual and looked up the codes and I know 47 and 48 is a air temp sensor faults. The air temp sensor is damaged from the spark arrester lid cutting into it and I assume that will just take a replacement to fix. What my question is code 43 and 41 are engine coolant circuit malfunction and engine above temperature range obviously like the engine is overheating. How can I tell if it's truly overheating the engine or if I have an electrical problem like the coolest temp sensor or wiring. Do I hook up a mechanical temp gauge and monitor it or are these things known for coolant temp sensor problems. I pulled the restrictor at the top of the pipe and it was clean. I pulled the thermostat and pop off assembly apart and everything looks good and clean their. What would be my next step for diagnosis.


  2. #2
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    Check the engine temp sensor wiring. If it hasnt had the exhaust tube bumper update chances are good that the wires for it are damaged.

  3. #3
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    I believe you can check both sensors with an ohm meter.

  4. #4
    I pulled both air temp sensor and coolant temp sensor out and they both ohm within specs. The air temp sensor was just over 1000 ohm and the coolant temp sensor was just under 1000 ohm. I ran it yesterday on the hose and within 15 to 20 seconds it started flashing the check engine light now today I made up a three way switch and cleared the codes and now today it runs fine on the hose for probably 10 minutes and will not reset any codes. At this point I don't know if I should take it back to the lake and try it again or just replace the two sensors.

  5. #5
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    Check the wires on the exhaust sensor and make sure nothing is damaged.

  6. #6
    Wiring all looks good and it does have a rubber bumper between the plastic exhaust and the expansion chamber. I assume that's the exhaust bumper update you were referring to.

  7. #7
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    Quote Originally Posted by LM53 View Post
    Wiring all looks good and it does have a rubber bumper between the plastic exhaust and the expansion chamber. I assume that's the exhaust bumper update you were referring to.

    Sounds like it yes.

    I would put it all back together and try it.

  8. #8
    Just got back from the lake and the MSX run awesome. All I did was pull the coolant sensor out tested good and put it back in, no recurring codes. I was impressed at how it took choppy water but I think my twin engine Sea-Doo jet boat would out turn this MSX and then again maybe I need more time on it.

  9. #9
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    MSX turns great with different sponsons on it.

  10. #10
    Resident electronics hacker UnityRacing's Avatar
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    And the Yamaha Exciter out turns the seapoo boats

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