[How To] Crank Position Sensor getting cranky

dnktng

dnktng

Joined
Jun 5, 2011
Messages
271
Location
Western Washington
Bike
2010 NT700V, 2015 CB500X
Well, It happened. Another Crank Position Sensor victim. The sad story...

...Went to Costco about 40 minutes away on an 85F afternoon about a month ago. Parked under a large shade tree. Always good to suiting up in the shade. Put it on center stand because it makes loading and strapping large Costco purchases easier. Went in, bought a couple items, no check out line (somethings wrong), and back to the NT in probably 8 minutes. It was a personal best time for Costco. No one can beat my time. Everything packed easily in top box. Crank, Crank, Crank... Dead! "I've heard this story before" as I assess the thought of my wife hooking up the trailer for a rescue mission. Gave it a second crank... nothing, and battery sounds like it doesn't have too much left. So, I wait and think how smart I am to park in the shade, and getting stranded at Costco is about as good as it gets. I can get a rotisserie chicken for dinner, buy a bed and sleep in the parking lot. Life is good.

Remembering that this is typical CKP (crank position sensor) failure mode, I gave 10 minutes to cool down, it fires right up and ride home.

Check for codes when I get home and there it is ...1 long & 9 short... 19. Tried recreating the problem after the next 5 or 6 rides and it never reappears.

So to refresh my memories on what I need I found these post on CKP failures:
https://www.nt-owners.org/forums/threads/hey-hey-its-crank-sensor-day.11365/
https://www.nt-owners.org/forums/th...-cranking-engine-during-starting.12106/page-2
https://www.nt-owners.org/forums/threads/changing-the-crank-position-sensor-tips.11305/
https://www.nt-owners.org/forums/threads/suddenly-wont-fire-😩.14289/#post-195086
These old post help so much. Finding them is the hard part.

10 years ago my local Honda dealer had the least expensive Honda parts I think in the country... but that has ended :mad:. So I bought a crank position sensor from Amazon for $60. It took 10 days before it shipped and 7 more to arrive and it came from PartsFish.com and Dillon Brothers in Nebraska. Best I could find for ThreeBond 1207B gasket maker was ebay.

Started the job this afternoon. Spent too much time trying to get access to the exhaust pipe nuts on the heads. Ended up taking the gas tank off to loosen the exhaust pipes. I have to laugh that to replace the Crank Position Sensor on the NT both mirrors have to be removed.

Since the oil has to drained I went to get a oil filter in my Honda parts stash. Laying on top of my stash is another crank position sensor. So now I have two spares with one going in tomorrow. I must have read the horror stories years ago and bought one.
 
Well, there goes that theory that if you have the part....you won't ever need it:rofl1:
If the exhaust wasn't in the way, it would be a very easy part to replace. Good luck and hope the job goes easy for you.

Cliff
 
Took a good look at the original Crank Position Sensor and Wheel before disturbing anything . There was some material stuck to the magnet (center bar in the yellow) on the CPS. I'm not sure how much that would interfere with it counting wheel tabs whipping around, but I know the new one didn't come with any magnetic fluff on the sensor. The sensor is 15 years old and has 58,000 miles, and we've all heard how they fail with age and the typical high temp after turning the engine off in usually warm weather, but it might have contributed to the problem. If this sensor had easy access I would have been tempted to clean it and run with to see if it fails again, but it's a PITA to get to I'd be insane to do this again in 3 months. Anyway, hearing that these sensors are getting harder to find and it only glitched out on me once, I'll keep it just in case someone gets desperate in the future.

Notes about the picture. The black dots in the yellow area must be OEM markers because the new one had the same. The wheel and magnet never touched even though this pic sorta looks like it might have rubbed.

1727390938013.png.
 
I believe most think the "normal" failure mechanism of these sensors is the extra heat makes things expand and causes a loss of continuity in the wire coil somewhere. After it cools a bit it connects enough to function again.
Glad it didn't strand you for long. The peace of mind makes it worth changing out.
If you are courious enough you could experiment with the old one.

Arknt
 
Old Subarus have the same issue. Easy to get to the cam posi sensor. Spray it with freeze mist. The engine computer has historical memory. Once the engine is running, you can actually remove the cam or crank sensor and the engine will continue to run. But not both. This kind of failure coupled with an engine that starts and stops itself all the time would be most inconvenient.
 
goldwingrider said:
I've just fitted a new crank sensor to my 2010 NT700 and I did not have to remove the full exhaust system, just the muffler. I left the headers in place, there is just enough room to remove the clutch casing without removing the headers.
Click to expand...
I said exhaust, but I should have said muffler. I didn't need to remove the headers either.
 
Add me to list of failed crank Sensors. 25k miles, no warning. Suspect the hot Texas summer where cooling fan went on a fair amount - possible overheating device ? Had hard time finding one in stock. Did not look at surface of failed device
 
By law, a manufacturer has to support a durable good for 10 years. Honda is better than that...and there is always the Junk yards....For those unclear, the device is brutally simple. I tightly wound verry thin wire . If a magnet passes by it, it generates a pulse...but not if the wire is broken. Opens up when hot....closes when cool. Clearly a manufactureing defect of course, which Honda doesnt want to spend the time fixing.
 
Coyote Chris said:
By law, a manufacturer has to support a durable good for 10 years. Honda is better than that...and there is always the Junk yards....For those unclear, the device is brutally simple. I tightly wound verry thin wire . If a magnet passes by it, it generates a pulse...but not if the wire is broken. Opens up when hot....closes when cool. Clearly a manufactureing defect of course, which Honda doesnt want to spend the time fixing.
Click to expand...
Actually there isn't a general law in the US that requires manufacturers to provide replacement parts for ten years. In the automotive world however, there is a law that if a vehicle is found to have a safety related defect within ten years of the date of sale, the manufacturer must provide a free remedy. This law sometimes leads folks to believe that the ten year window covers all replacement parts.

The failure of the crank sensor is actually not a manufacturers defect but an expected mode of failure based on its construction and operating environment. The sensor is an inductive sensor consisting as the Coyote mentions a tightly wound, very thin, enamel coated copper wire which generates a voltage pulse when a ferrite core passes by it. The copper wire has a vey high coefficient of thermal expansion and thus expands/contracts with each heating/cooling cycle. Over time these thermal cycles will cause fatigue of the wire resulting in the breakage of the wire and an open circuit. As the sensor cools, the wire will once again make contact and appear to operate normally. The other failure mode is that with the constant expansion/contraction of the copper wire, the enamel coating will abrade through resulting in a short circuit of the copper coil which causes a voltage variance that the ECU no longer recognizes.

I hope this info helps.

Mike
 
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