Oddity with Tire Pressure Sensor - K-Bikes.com - Excellence in Motion
 
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post #1 of 6 (permalink) Old May 27th, 2008, 11:02 pm Thread Starter
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Oddity with Tire Pressure Sensor

Ever have a tire pressure sensor issue? On a hot day, I mean over 100, in the sun, the bike was so hot I could not touch the levers to move it into the shade. On starting the bike it faulted indicating 0 psi in the front tire. Pressure was fine, but I suspect it was the heat...after the evening progressed (cooled) the problem resolved itself. Odd.

The only curious thing is how could heat (I don't know the design) be the issue....or am I grasping at the obvious...which isn't so obvious. Either way it's intermittent (1 session) and bound to get you the "It cannot happen" look from a service manager.

However, even though the tire was fine, it was amazing how big a distraction that flashing triangle is. On older K's you could take it (the ABS at least) out of flashing in your face mode for a period of time. I will have to bring electrical tape with me if this happens again. Isn't some technology an annoying attempt to idiot proof the planet? That's why I have the Velocette, it don't need no stinking sensors.
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post #2 of 6 (permalink) Old May 28th, 2008, 4:44 pm
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The tires normally heat up when riding, so the TPS sensors have some temperature sensing built in which it uses to compensate for pressure variations due to tire temp. Maybe you just hit a weird glitch. All you can do is keep an eye on it and see if it happens again.

I had the SmarTire system on my LT which reported tire temp. Riding two-up at 85+ mph up I-15 in 115 degrees, the rear tire went well over 190 degrees. Pretty scary if you think about it.

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post #3 of 6 (permalink) Old May 29th, 2008, 12:10 am
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I recently had a problem with mine reading 7 lbs low on both tires consistantly . The red triangle flashing telling you both tires are low is very distracting. I made a appointment to get it checked out at the dealer the following friday after noticing the problem. I checked the tire pressure with a guage before leaving for the dealer and wouldnt you know the tpm was working perfectly now. The service manager listened to my story and agreed that it was odd but said to log any further problems in a notebook with dates, temps, pressures, and readings. He checked his system for any other like complaints but found none. He said he would converse with his contact at BMW with the data log I agreed to collect for him. I have ridden my GT about 250 miles since last friday (mostly commuting) with no further problems. The tempuratures have been cool however so time and heat will tell.
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post #4 of 6 (permalink) Old May 29th, 2008, 2:40 pm
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I had it happen once, turned the bike off and on again and all was OK.

I asked my dealer about this and his explanation was:
The TPC works with sending units in the tires and a receiver. If a reading was faulty or some interference occurs, the BC can give you false readings. Turning the bike off and on resets it. Only if it becomes a frequently returning issue there is something to worry about.

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post #5 of 6 (permalink) Old May 29th, 2008, 7:22 pm
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Quote:
Originally Posted by beavtm
Ever have a tire pressure sensor issue? On a hot day, I mean over 100, in the sun, the bike was so hot I could not touch the levers to move it into the shade. On starting the bike it faulted indicating 0 psi in the front tire. Pressure was fine, but I suspect it was the heat...after the evening progressed (cooled) the problem resolved itself. Odd.
Surprising that it indicated anything at all when you started the bike. Normally you have to ride for a bit before the sensor starts sending. I guess there's some kind of acceleration sensitive switch in the sending units, presumably to save the battery.

Maybe it got so hot that the electronics in the sending unit got messed up? Batteries and switches and whatnot are temperature sensitive.

The TPM sensor definitely takes temperature into account. It always displays "cold" tire pressure, even when the PSI goes up significantly after the tire warms.

I had this glitch on me once where the tires cooled off faster than the sensor while I was stopped on a cool day. When I restarted the bike the sensor read several pounds lower than expected, which triggered the hazard warning. After the tires warmed back up the pressure reading went up, but the warning light stayed lit until I stopped and restarted the bike -- annoying.
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post #6 of 6 (permalink) Old May 29th, 2008, 10:33 pm Thread Starter
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Don't read too much into it

The bike was ridden 'as per the case' to get the readings. It read 0. Pressure was dead on cold with two gauges. Several power cycles and waiting caused it still to read 0 once on the way. It only corrected itself after the ambient temperature dropped about 30 degrees. The trick to this is the sensor thought it was working, there was no fault...either that or 0 is the default value displayed on a sensor failure...probably legal stuff...If the sensor or pressure circuit faults, assume the worst and display 0.

I even dropped and raised the air pressure thinking something was sticking but to no avail. These things are a pain in the butt and probably will not be replaced if they fail (that's my story). By that time I'll have figured out how to defeat the circuit.
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