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fi code 21 crank shaft sensor

17075 Views 8 Replies 3 Participants Last post by  Lordfupa
Hi guys I need some help on the crank shaft sensor. I tested the resistance it check at 455 ohms but failed the voltmeter test. Also failed the infinite resistance test so I am guessing its fried. I check the wires on it and the black one had some wounding in it, possible grounded on the frame and cause it to die.

Do I need to drain the oil to get the sensor out? The part is called pulsating coil sensor.

Prior to this I was having a hard time starting the motorcycle. It felt like the ignition switch was loose and not cranking so I check that switch expecting water damage but it was so clean so it puzzled me. After that the 10A fuse from the fi had some white stuff on if so I replace it with the spare then the Mc started running again until I went outside and it just died. There is some priming sound under the tank but there is no crank when I start here up, then fi light turns on code 21. I am guessing the sensor harness got shorted because I gave her a wash then started her up.
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Hi IC,

I suspect your crankshaft sensor is still good (with 455 ohms resistance across the crankshaft sensor terminals) -- but it seems one of the crankshaft sensor wires is grounded to the bike's chassis. Please note that, unless you have a "peak voltage adapter" (a specialized electronics device thingy) eh you cannot reliably measure/inspect the "Crankshaft Sensor Peak Voltage". The "infinity test" is actually a test if one (or both) of the crankshaft sensor wires is (are) shorted to the bike's chassis ground -- no big deal, just big words.

That being said, trace the wires from the crankshaft sensor upto the ECU for any damage -- insulate with electrical tape any exposed (wounding?) wiring. Do the resistance and infinity test again. No need to do the peak voltage test (unless you have the device thingy mentioned above).

If all is good ==> re-assemble everything back, then attempt to start the bike. If the bike still throws you the code 21 (fingers crossed), then your crankshaft sensor is indeed fried.

I hope your crankshaft sensor is still good -- it's (p/n 59026-0018) a cheap usd60.00 part, but hassle to replace. Yep, you will need to drain the oil, open the clutch cover, replace the crankshaft sensor, replace the clutch cover gasket (p/n 11061-0165) with new, put sealant everywhere, close the clutch cover, and assemble the yada yada yada.

Enjoy and ride safe! :)
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So I trace all the wires from the main relay and found the yellow red one cut!<which is part of the ignition circuit> solder that one and I put some epoxy resin on the expose wires of the crank sensor then cover with electrical tape.

I fired her up and I could not hear the fuel pump priming<it was working fine before>the meter gauge is acting crazy like the tacho is going up and down then rest on the zero and then bounces. Is it a weak battery? Or something still in the electrical that I haven't figure out. I'll try to jump the battery with my car battery see if it fixes it. The fi code is now 39 ECU Read Error

In addition I check all the main relay they are fine. No fuses are blown also.
When you did the soldering thingy, eh did you disconnect the ECU (and the meter unit too)?

If yea, maybe it's simply a loose connection -- just try to disconnect and reconnect.

If nay, uhm, do you have a friend who is willing to test swap ECUs so you could confirm that yours isn't fried? Static electricity (usually from not-so-adequately-grounded soldering) does nasty things to electronics (aka ECUs).
It gave me another fi code this time 62 which is the valve actuator when I jump her to the car battery. I can now hear the priming of the fuel pump but there is some strange noises under the tank like a clunky sound was it the starter motor? There is now a click sound when I try to fire her up but still no cranking<like back then when it reported the crankshaft sensor the difference is the clicking sound which was not there before>.

After I disconnected the car batt tried starting her again and went back to code 39 this time still ecu comm error. The clunk noise under the tank is now gone though and fuel pump priming is back. The meter is back to normal no more bouncing tacho.

Unfortunately there is no other ecu I can swap with.
Yay! A working (priming) fuel pump is a good sign that your ECU is still functional, as the fuel pump relay is wired directly to the ECU. :)

It looks like you just need a new battery (p/n 26012-0556 BATTERY,YT12A-BS,12V) -- 100 bucks orig Yuasa from the stealer.

If your battery is still good, I would re-check the yellow/red wire (starter relay) connection. A break on that wire will not allow you to start the engine.

Again, I would like to exaggerately stress that the electronics (i.e. ECU, meter unit, gear indicator, Power Commander, etc) should be disconnected before any soldering be done.

3njoy and rid3 saf3! :)

p.s.#1 Funny though, I too tried to jump start my bike before (weak battery). Alas, exact same symptoms. Solution: new battery.

p.s.#2 The clunky sound you hear is just the sub-throttle valve actuator resetting its position prior to engine start -- perfectly normal (and a well documented issue in Youtube).

p.s.#3 Hey Oz! A Tropa (beer buddy) badly needs your help (ECU test swap). Although, it looks like moot now prelude to new battery. Hehe
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