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Apparent CMP Sensor issue, Stumped!

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  • Apparent CMP Sensor issue, Stumped!

    Hi all, and thank you so much for being here.

    I'm pulling my hair out, trying to solve a crazy problem with my (brand new) 2020 Suzuki DF50ATL, which went for an unauthorised swim in the river yesterday. After pulling it out and drying it off, I've got no spark and a dead motor. I went through all the recommended steps, pulled plugs and blew compressed air through everywhere, cleaned contacts, etc. etc. The beep code tells me there's a problem with the CMP sensor, but having tried out all sorts of things I'm doubting the accuracy of that. Here's why:

    I actually have two of these motors, identical, powering my big lumbering houseboat, so I'm in the position of being able to swap parts between them. I swapped the CMP sensors- no change. I swapped the ECMs- no change. I put the ECM from the "good" motor into the "bad" motor, got the same beeps, then put it back into the "good" motor, and got those same beeps again, one time, from the "good" motor. But after that, the "good" motor started up fine, and the beeps disappeared.

    I followed the steps listed elsewhere in this forum for testing the CMP sensor-- found the wires and their functions, got a solid 12V from the plus wire and a solid 5v from the signal wire, as relates to motor ground. I'm trying to think of a way to hook up my multimeter to the sensor while it's connected to the ECM and hand-cranking, but so far I haven't found a way to do that w/o piercing the waterproofing of that connector... Any help with that would be appreciated, but I'm going back now to try again.

    Here's two "of courses":

    Of course, I've got an appointment on the drydock, two days ride away, this Friday, that I will seriously hate to miss. And of course, all the local Suzuki shops are run by thieves and charlatans, or are much too busy (it's May) to help me. Only one said "sure, but sometime around mid-August!"

    Oh dear oh dear.
    Last edited by BigPill; 05-17-2021, 08:28 AM.

  • #2

    I succeeded in checking the function of the CMP sensor by threading thin wires out of the connector at the sensor itself, to my meter, then cranking the motor by hand. The voltage switches back and forth between 5.2V and 0.3V, just as it should. I also checked continuity between the connectors at the sensor and at the ECM, all good. So to my mind, that means the 2-beep/ 4-beep warning signal is false. Right?


    • #3
      Someone? Anyone? Anything?
      I don't mean to badger anyone, but I'm really sort of on my knees here.


      • #4
        If you swapped the computer and it came back with the same code you would think that there still is a problem in the wiring between the sensor and the ecu.
        Check and make sure that the signal voltage is switching between zero and five volts at the ecu.

        Also remove the connectors from the crank sensor and blow it out and check to see what voltage you are getting at the sensor and at the ecu.


        • #5
          I should have put while cranking in that post just incase you were confused.


          • #6
            Hi, and thanks so much for getting back to me. Yes, I absolutely would think there's a problem in the wiring before the computer, but I checked everything, including voltages while cranking and everything else that seemed to make sense, too. It's all been blown out, dried off, and v-e-e-r-y carefully inspected. I don't want to get too too far ahead of myself, but what I'm speculating now is that the problem is indeed electrical, but just not that which the computer system is telling me it is-- somewhere else, and I could (actually, I am) go crazy trying to find it.

            But I'll try to stay on the pavement here:
            Has anyone had experience with false messages coming from the warning system of a DF motor? And can it be the case that something in the ECM gets "tripped," and the module won't deliver spark until it gets "reset?"

            Can an ECM be "reset," or "reflashed?" Would hooking up a proprietary laptop with Suzuki's own software do a better job of diagnosing than the built-in system?

            Swapping the computers was one of the first things I did, even before I'd completely dried everything out, so maybe whatever short caused the original problem was still persisting at that time. I haven't dared to check it again, because I really, truly don't want to risk damaging my one good ECM in the service of diagnostics... I've read that they can be sensitive to static, and so on...

            I'm in touch with the one dealer here, but the boss is on holiday right now (how dare he!), so I'm learning a big lesson in patience.

            Of course I'm tempted to launch a long discourse on the dangers of proprietary software and the "right to repair," but I'm afraid if I were to get all Ma**ist on you, I'd really be putting my foot in it.

            Thanks again, and I'm eagerly awaiting any advice I can get.


            • #7
              ***, interesting. I seem to have been censored for mentioning a certain 19th-century historical figure, who developed economic theories that are controversial today. Gotta respect the dedication to keeping it apolitical!


              • #8
                Oh my! Now I seem to have been censored for using a very common and (I always thought) totally inert three-letter interjection which starts and ends with a W. OK, I'm getting the hang of this, I hope!


                • #9
                  Check the voltage at the crank sensor and at the ecu, while cranking some times Chrysler’s give you a cam sensor code and it is actually a crank sensor fault.


                  • #10
                    Just looking at your post again, I would want to see less than .3 of a volt on that’ ground

                    That ground seems high, the ecu may not be seeing that as low.
                    check the ground for the cam sensor 300mv seems high l would think around 40mv.


                    • #11
                      Thank you, Redlowrey, you're a hero. But unfortunately, the motor still ain't giving me love. Here's what I did today, between rain showers:

                      I checked the CKP sensor for voltage, but the test was faulty or inconclusive, so I just swapped out the CKPs between the two motors. No change in symptoms.

                      I checked through all the wiring again for shorts or breaks, didn't find any.

                      I installed the CKP sensor from the "bad" motor into the "good" motor, it ran fine.

                      So I went ahead and swapped the ECMs again. The "good" motor, with the ECM from the "bad" motor started up fine and purred like a kitten. The "bad" motor with the ECM from the "good" motor exhibited the exact symptoms as ever: 2 beeps/ 4 beeps, and no spark. I swapped the ECMs back, no change in the "bad" motor, the "good" motor gave the 2/4 beep once, then found its camshaft and started up fine again.

                      I swapped the CMP sensors again. No change, so now the "good" motor is running fine on both sensors from the "bad" motor, and the "bad" motor is still not sparking.

                      I threaded fine wires into the connector at the base of the ECM of the "bad" motor, and checked the voltages. First I checked the CMP sensor (meter + Probe to the yel/blu wire and - probe to the blk/wht wire), and hand-cranked the motor. It toggled perfectly between 5.01V and 0.3 or 0.29V (yes, 300mV).

                      Then I checked the red/blu and blk/wht wires of the CPK sensor, also at the ECM connector while hand cranking with the key on. I saw it toggling between a solid low of 0.2V and a variable high of between 0.08 and 0.12V. Turning over the motor by key yielded about the same result-- it was just a bit hard to read with all that flickering.

                      I checked once more for shorts or breaks, found none.

                      So it sort of feels like I'm back to square one. I made an appointment with the local shop, but I'm still very skeptical of them, and it's not for a couple of weeks. Hmm.


                      • #12
                        I checked specs .3 volts is ok, l don’t think that the cam code will go away till the engine starts, did you swap the coils the internal module in each coil may have got water inside and shorting the five volts that the computer uses to turn the coils on and off.
                        So you might keep thinking you have a cam sensor problem and you have not.
                        l assumed you may have been using an oscilloscope, checking the crank sensor with a multimeter won’t give you the peek to peek voltage you need to see when cranking the engine.
                        Mate there can’t be much wrong you have swapped nearly everything.
                        If it still does not start when you swap out the coils l will tell you how to check and see if the computer is turning the coil drivers on and off.


                        • #13
                          Have you checked the operation of the safety lanyard and blew it out and checked it hasn’t been tracking.
                          I should have asked in my first post how the engine went in the drink, was it running, did it go right under, was it salt water or fresh.

                          I assume you checked for battery voltage going into and out of your coils and injectors with the key on.


                          • #14
                            I hope you haven't been trying to start this engine by bypassing the key, because if you have it won't start, there will be no ignition or injection pulses.


                            • #15
                              Hi, and sorry for my absence-- I had to get some stuff done, but I'm back now. And thanks again Redlowrey, you've been incredibly helpful. I'm going to do a quick recap of my sorrows here:

                              Cause: the whole motor, a 2020 DF50ATL, went underwater for a few seconds. It was fresh water. Both motors are hanging on a fat steel bar that I welded to the steel hull of my 18m houseboat; I'd done a bad weld, one side broke, and the whole bar drooped down far enough to dunk the starboard motor. It was running at the time. I pulled it out by attaching a chain winch to the bar and lifting it back up. Only myself to blame.

                              Symptoms: no spark. 4-2 beep pattern, occasionally 2-4.

                              First measures: checked for water in the oil. Dried everything out. Blew out the cylinders with compressed air through the spark plug holes. Hand cranked, then tried with the key for a while, no change. Checked all the fuses and relays. Carefully checked all the connectors that were immediately accessible, dried and sprayed them with contact spray.

                              What I've tried so far, involving swapping parts between my "good" motor and my "bad" motor: swapped CMP sensors, CKP sensors, ignition coils, ECM. Everything works fine on the "good" motor, still no spark on the "bad". Checked all the sensors for resistance and/or voltage, they all seem to be working fine. That the 4-2 beeping won't reset until the motor runs is an important point, I think; it saves me worrying about sensors, at least for now.

                              I'm not trying to bypass the key, also not using an oscilloscope-- don't have one handy. I haven't checked the safety lanyard per se, but I've got a double-key starter panel (with one lanyard for both motors), and the other motor works fine.

                              Still, and always, the exact same symptoms persist. That the 4-2 beeping won't reset until the motor runs is an important point, I think; it saves me worrying about sensors, at least for now.

                              I'll check voltages at the coils and injectors and report back.

                              My suspicions lie now (in order of both gravity and difficulty) with the neutral switch, rectifier, and finally the stator coil. I'll be checking those next.

                              Ah, BTW: when I first checked for water in the oil, I hadn't yet even tried to turn the motor over, and it was tilted up all the way. The oil looked fine (I know what contaminated oil looks like), and all I noticed was that the level looked high, which I put down to the fact that the motor was tilted. But when I checked the oil again a few days ago, I discovered that yes, it was contaminated (I'm thinking that on my first check, the water was still just sitting at the bottom, not yet mixed up in the oil), and overfull, even tilted down. So I drained the oil for a full day, then changed the oil and the oil filter. That's all good, but still no spark.

                              Just to be clear: my understanding of motors comes from rebuilding motorcycles a long time ago, and my electronics experience is mostly from rebuilding audio gear. So it's fair to think of me as an outboard noob! And yes I'm definitely aware that a little bit of knowledge can be a dangerous thing...

                              Any further tips will be greatly appreciated!