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  1. #1

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    2001 Seadoo GTi MPEM doesn't recognize dess

    Been a while since I have been here, so thanks for looking. I did search for mpem dess, but didn't see anything relevant.


    2001 Seadoo GTi 717, almost completely redone. Problem is that I keep going through MPEMs. First original stock one stopped working 2.5 years ago. Had a fun day on the water, pulled up onto trailer, took home and went to start to flush and nothing. No response, no gauges, no start. No fuses blown. Had dealer check computer... MPEM gone, unrecognizable, even with replacement dess post. Then got aftermarket... that stopped working within a year... now on 3rd mpem, which is OEM. No fuses blown anywhere, but simply will not recognize dess key/post. Replaced dess post with three different known working ones. (tested on my XP) Ski has been sitting for a few months under good cover, leaned up to keep water out.

    On the current OEM one, if I push the start key 5 times, I get diagnostic mode. This would indicate the mpem is not hosed, correct? After it beeps for diagnostic, I place key on post and press start again. 2 beeps. This is indication its the wrong key or doesn't see the key, correct? If I wait some time, put dess key on and press start, I get one long beep, indicating what I believe is mpem thinking its wrong key. Even tried my XP key, and gauges don't respond placing key on, nor does it react with magnet near post. But gauges do respond when pushing start... just one beep.

    Took digital multimeter and checked continuity on all three wires (white, black/yellow, black) from dess post down to mpem. All positive continuity, with only slight ohms of resistance. Took plug off mpem and tested wires from MPEM plug up to dess post with key off and key on... circuit open with key off, and closed with key on. Tested black ground continuity and resistance from mpem to back of ski. All tested okay.

    So is another MPEM hosed? Doesn't seem to be the case, being that it goes into diagnostic. Seems that it just can't "see" the dess post, even when replaced with working one.

    One concern is that I have seen some discoloration of some wires coming off the MPEM going to the back of the ski. Some wires look almost burned/browned from heat, and wires seem really "stiff", but that could be age.

    Click image for larger version. 

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    Should I try yanking and replacing the wiring harness with OEM replacement off eBay and see if that works? Just don't want to keep blowing through MPEMs on this ski... expensive... I think it has to be a short or bad connection somewhere, but just can't find it.

    Thanks again for looking, and any help you might provide!

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  2. #2
    wkuadam07's Avatar
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    Sounds like you need to get it plugged up and program the key again. On a side note, i have seen one other ski that ate Mpems and it had a bad rectifier. The rectifier was allowing AC voltage and too high DC voltage to charge the battery and was cooling mpems. Check the battery leads for AC voltage with the ski running when you get it going, and check to make sure the DC voltage isn't too high. If it is disconnect the rectifier and check the voltage from the stator, the problems could be in the stator to begin with. The manual or forum searched will tell you what voltages you are looking for, you can also check the impedance/ resistance of the stator and make sure they are within the specification for that model. Also, you aren't jump starting this unit are ya? Jump starting KILLS mpems. They are very sensitive to high voltage and voltage spikes. It's almost common for a voltage spike to cause you to have to reprogram a key.

  3. #3

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    Quote Originally Posted by wkuadam07 View Post
    Also, you aren't jump starting this unit are ya?
    Thanks for the feedback. I am waiting on a replacement wiring harness, which will hopefully get it started and I can test the stator/rectifier. Just strange that if that were the case, it would have cooked the mpem altogether and I would get no diagnostic mode. Odd that if its the stator/rectifier, it would smoke only the detection of the DESS key leads... but will check it out, thanks.

    But as to programming the key... the mpem doesn't even "see" a magnet being placed close to the dess post. On my other seadoo, if I put a magnet near the post or another key on the post, I get a reaction from the gauges, and one beep when pushing start.... this one doesn't even do that. But this one DOES go into diagnostic mode when pressing the start 5 times with no key. So its like the mpem just doesn't see the post/key.

    And yes... I know to never ever jump a ski... well at least not from a car battery. I have "jumped" a ski by using a thinner set of jumper cables from another ski next to me on the beach, but not while the other ski is running. Saved my @ss when I had an old liquid battery "brick" on me while on the water... thus why I run only AGMs now...

    This ski has a nearly new, fully charged AGM battery, as all my skis do.

  4. #4
    wkuadam07's Avatar
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    Yeah, i forgot to mention... that harness actually looks pretty normal to me. The discoloration you are seeing is color bleed from the black loom, or black from an exhaust leak inside the hull of the ski. Most of the wiring in older seadoos looks like your picture. Also forgot to mention, make sure you clean all your ground wires on the front of the motor, bad grounds cause a world of electrical demons on these things.

  5. #5

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    thanks wkuadam07 for feedback again.... grounds are all good.. went through last time mpem died and sanded/wire brushed all down to metal and used non conductive grease on all. Still good. But will test continuity/resistance on all again to be sure. Will let you know what happens with replacement wiring harness when I get it installed.

  6. #6

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    Thank you wkuadam07 for giving me some ideas and trying to help.

    I am happy to report that my issue was apparently my wiring harness, and I got her fired up again and running strong! Woooohoooo! Not the (expensive) MPEM. I replaced harness with a replacement off eBay that was from the midwest and only in fresh water, to which the wires were very pliable and soft, unlike the ones on mine, which were very rigid and stiff.

    Upon closer inspection of mine, by taking off the plastic "face" of the plug to reveal the actual metal female receptacles in more detail, it seems that someone prior must have jammed a testing plug from ohmeter all the way into the holes, thus expanding the metal female plug jackets to where they made intermittent contact, or in this case, eventually no contact. Having worked with electronics for many years, I know not to do this. Always test from the backside of the connection or gator clips.

    Anyway... I just wanted to post so others experiencing similar might have an idea of what to look for. If the MPEM goes into diagnostic mode with 5 pushes of start and your gauges react then, it's probably going to be a bad connection to the mpem or the leads from the dess post, or the dess post itself is bad, because the computer is "there" and probably not smoked. One way yo test the dess post is hold a magnet near it.. if the gauges react, the mpem sees it. I thought mine was gone... twice, and bought 2 replacements to try and solve this issue, but all three are actually good.
    Last edited by MacAddict; 09-18-2014 at 04:01 PM. Reason: added to headline, description

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