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Discussion Starter #1
I have an 04 R1, its my daily driver. Recently Ive noticed that my temp guage will fluctuate in an implausible manner. 199 to 170, back up of 190s down to 150, up to 160 bck down ect, You get the idea. It might be a resistance issue. I replace the temp sensor with an after market on and after three days of working perfectly it started to do it again on a hot ride home. Bike never over heats but does get hot enough to turn on the fans since its 95 deg. Anyhow I though it might be something in the harness cause it would have been moved when I installed the sensor. I tried moving the wiring around when the engine was hot but could not really duplicate anything significant. Does anyone have any experience with this. I know that the signal goes straight to the ECU and the supply is tied in to a veriety of other sensors.
 

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A simple resistance test can tell you if the sensor is in specification.

Put the coolant temp sensor in a suitable container filled with coolant, ensuring the terminals do not get wet. Connect multi-meter leads to each terminal (02-03 r1 is green/white and black/blue). Using a thermometer and multi-meter, heat the coolant, noting the temperature and resistance. The 2002 r1 resistance specs are 5.21~6.37 kΩ @32° F and .29-.35kΩ @176°F. The 2004-2006 should be similar. Repeat to ensure consistent function.

Generally speaking, the senor has a negative temperature coefficient, meaning as temperature increases, resistance will decrease, allowing more amperage to pass through the sensor.

I'm assuming you've got a proper coolant level and concentration.
 

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Discussion Starter #3
Checking a sensor in a static enviromet is easy but being that it only happens when hot would require a dynamic enviroment which would be impossible. Yes coolant is full and 50/50 . I change it every year. It seems to occurre when its hot and engine is hot. I have a hard time beleiveing it sa bad second sensor. I was going to replace the injection harness cause there are shared splice points in it as that ckt . If its in the signal ckt that goes through the ECU then that would be hard to prove. I guess we will see.
 

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If you’ve been doing this as long as I you would realize no resistance test is static, the wire heats up as you send voltage through it and that itself can change resistance of circuits by .1ohms or more. Never say impossible my friend. You can heat the coolant to 200 degrees or whatever temperature you’d like. Test it. That’s the only way to know for sure, you can play guessing games all day, but until you unplug the thing and put an ohmmeter on it, only God knows.

If there’s a short somewhere, unplug the harness from the ECU and test it while tugging on the wire. Shouldn’t be that hard.
 

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Discussion Starter #6
What your missing is that this is most likely not the sensor. Ofcourse i can heat the sensor but i can not duplicate the environment when this happens ie: hot engine, hot harness, the vibrations ect. Ive already ruled out the sensor. That's why Im looking else were. It becomes a process of elimination.
 

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So you are telling me that you are having bad readings of a temp sensor. You bought a piece of junk aftermarket sensor to replace the one you thought was bad, and you never did a resistance test to verify the problem. Beautiful.

A resistance test can tell you if something shorted and damaged the sensor, if that sensor is in spec, you test the circuit. Start at the component, then verify power and ground, this is basic.

Go ahead and keep throwing more money and replacing with half rate parts until it goes away lol. That's what we call in the industry a money maker hehe.
 

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Discussion Starter #8
Here we go. The fact that the issue did not change with a diff temp sensor says its not the sensor. Second of all performing a resistance test does not tell you the whole story if the issue is not with the sensor. So since your the genius you tell me. If i removed the sensor to test i might as well replace it. Now that we know its not the sensor (again) and your so smart what would you do. Oh ya measure the resistance of the sensor again cause it could not possibly be a harness, ECU, or anything else. Some of you are stuck on the sensor. FYI just heating up the sensor and checking resistance tells you squat depending on the failure. Only if it is outright messed up might your multimeter pick it up otherwise with such a quick fluctuation it might not even be catch it when measuring it.
 

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Discussion Starter #9
GOT IT FIXED. I replace the short harness that connects the TPS, intake air temp, coolant temp sensor and injectors. Not only did it correct the irratic temperature but it corrected the fluctuating idle and I used to have a little blip in the throttle when first taking off. All that is gone. Thottle is super responsive out of a turn and from a stop now.
 

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Here we go. The fact that the issue did not change with a diff temp sensor says its not the sensor. Second of all performing a resistance test does not tell you the whole story if the issue is not with the sensor. So since your the genius you tell me. If i removed the sensor to test i might as well replace it. Now that we know its not the sensor (again) and your so smart what would you do. Oh ya measure the resistance of the sensor again cause it could not possibly be a harness, ECU, or anything else. Some of you are stuck on the sensor. FYI just heating up the sensor and checking resistance tells you squat depending on the failure. Only if it is outright messed up might your multimeter pick it up otherwise with such a quick fluctuation it might not even be catch it when measuring it.
After you ohm out the component you then move to power and ground, which would then be the harness which you can also ohm out. This is standard testing procedure taught at trade school, not my personal method. I would bet that the faulty harness had an abnormal resistance. And if you wanted to simulate the exact operating conditions you would just do an applied voltage test on the bike while running, which would in fact be the exact condition.

I never insisted that it's the temp sensor, only that you test it to verify.

In your case after the second component you managed to guess the right fix, all I'm saying is the only way to know for sure and to save time and money is to do the proper test. Had you tested the thermostat in the first place you wouldn't of had to buy the aftermarket one.
 

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Discussion Starter #12
Your correct in ther perfect world. Im a 30yr BMW master tech. Being that this only happened at above 200deg that performing a static test of the harness would most likely not produce the desired results. The heat can changes the resistance without an open. These scenarios can be very difficult to isolate especially if it occurs within a module itself. I got lucky on this one.
Thanks for your feedback though. Always appreciated.
 

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Discussion Starter #15
True but in my world politically correct does not always work. I can check voltage and it would be normal. Introducing the load in a completed ckt is something else now introduced the environmental conditions when the failure takes place. That's the trick. Lol liking the back and forth
 
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