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Temp sensor testing, 2015 Rancher

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Had a local crop scout drop off a 2015 Rancher ES, said it was cutting out when it got hot, and he thought it needed a fuel pump.


Ordered a fuel pump, and let's just say these 2014+ models are completely different than the OBS.  Remove tank covers (which is really easy) and the ECU and all the crap that used to be under the front fender is now right on top of the fuel tank, and the fuel pump unit is huge and goes right in top of the tank, held in place by a lock ring.


Anyhow, this guy's stuff was obviously used and abused.  3-4" of mud in the skid plate under the engine, with a valley for the front driveshaft.  Battery box was completely full of mud.  Basically used in the fields and never washed. 


So, I sprayed everything off so I didn't get mud down in the gas tank when I removed the old pump.  New pump arrived yesterday, got it installed in the tank without any real difficulty, and fired it up.


Immediately the fan and temp lights come on, and it throws a ECT (coolant temp) sensor code.


The last time I've seen this was on my buddy's kid's 2013 420AT, and he said brought it to me with the same symptoms.  I had the wife's old 2009 so was able to test that one swapping parts, and it was a bad ECU.


I've printed off the below instructions on testing the ECT on this one, but I want to make sure I'm following them correctly.  Don't have the MCS (Motorcycle Communication System, dealer tool) so will have to make it work with a voltmeter.


So for step on, turn the switch on, and it says "check sensor with the MCS" and look for 0V.   I assume that means check the sensor with the wiring harness attached to it, so would I check the wires going to the sensor at this step?  Step 2 is "Disconnect the ECT sensor connector, and then check the sensor with the MCS"


I hate electrical work, and this guy needs this thing back sooner rather than later as he uses it working.


Any of you electrical gurus dumb this down for me to troubleshoot this after work?  @AKATV @retro @Melatv






ECT sensor_Page_1.jpg

ECT sensor_Page_2.jpg

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Got this one figured out this morning.


I never did figure out how to test the sensor using the instructions above.


I did go out to my Rincon buddy's house, pull the temp sensor off of his kid's 2013 Rancher to swap on and see if it would work.  Problem is, Honda changed the sensor.  The readings are the same in the FSM for both, but the plug/clip is slightly different, so the sensors don't interchange. 


He has a brand new 2023 DCT Rancher, and so I just unplugged the sensor on it, plugged my sensor into the wiring harness, and turned the key on.  Fan and temp light didn't come on, so that tells me it's not the sensor.    I will say I'm NOT a fan of the giant middle section of plastics that lift off the machine on the 2014+ models (tank covers).  I spent 15 mins trying to get all the posts into the grommets on that 2023 bike, finally gave up and told him I'd do it after I change the oil on it (it has 125 miles on it, so due for the first oil change).


So, with the sensor ruled out as the issue, I figured checking continuity from sensor to the ECU was next.  Found no continuity on the blk/blu wire.  Traced it and found it had broken off where the ECT little harness meets the main harness loom.  Had to strip back some insulation so I could use a little heat shrink/solder tube on it.  Once I did that, no more fan or temp light/ error code 7.


So, at least it wasn't the ECU.  That wire must have been iffy and when I pulled all that crap off the back of the gas tank it gave up and broke.

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