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I had a low tire indicator show up on the dash today while driving home. It was flashing. I continued to drive, (only a mile from home) since there was no indication of anything going wrong with the tires. Then, the indicator stopped flashing, and went to steady. Then, by the time I hit the brakes to turn down my road, the indicator was gone.

So, I checked all my tires, and with my very old accutire gauge, they all showed 34.5 (35 being the spec). I hope to not see that again. Anyone else seen anything like that?
 

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Out of curiosity, have a phone cord or NAV cord plugged into the lighter socket or pwr outlet ??
 

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Check your tire pressures COLD. Sensors go off at about 30 psi, and with 35 psi hot, you should be pretty close to that minimum, hence the intermittent signal. I run mine at 35 cold. Spec is 33, by the way. Remember every 10ºF temperature differential means 1 psi. If there's a problem with a sensor or anything with the system, you'd get the 'TPMS' light on the dash. When it's the low tire symbol, one or more tires are low in pressure. Good luck.
 

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QUOTE (Tom Brodrick @ Aug 22 2010, 10:38 PM) index.php?act=findpost&pid=351194
I had a low tire indicator show up on the dash today while driving home. It was flashing. I continued to drive, (only a mile from home) since there was no indication of anything going wrong with the tires. Then, the indicator stopped flashing, and went to steady. Then, by the time I hit the brakes to turn down my road, the indicator was gone.

So, I checked all my tires, and with my very old accutire gauge, they all showed 34.5 (35 being the spec). I hope to not see that again. Anyone else seen anything like that?
After 5 mos my indicator lit up and I checked my tires with a digital guage. My rt frnt tire was 29.5 lbs. I added the necessary air and all is well. Another plus feature that seems to be working as designed.
 

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Mine came on the other day just to flash for about 30 seconds then went off. All were at 33 psi but the weather went from 100 degrees to around 75 with a nice cold front and rain storm.
 

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The blinking TPMS happened in my wife's Sonata while she was talking to me on the phone. The phone wasn't the issue because she had spoken to me plenty of times beforehand. Gotta love Bluetooth. She was driving and said that the "horseshoe" light suddenly started blinking. Turns out it was the outline of the tire with the "!" inside it. So I asked her where she was when she saw the light blinking and she said it was near a police station. A quick Google search turned up lots of content about Hyundai TPMS being extremely sensitive to interference. So I checked the frequency used by that police department and found out that it is almost exactly half of the TPMS frequency used. Since that'd make local police and fire radio frequencies a harmonic of the TPMS frequency, strong broadcasts can out-shout the signals from the four sensors. The blinking apparently means the car lost communication with some or all of the sensors. The light was blinking for about 15 seconds and then stopped blinking and remained off.

It will also blink when driving near the other police station closer to home. But not all the time. Apparently the missing link is that they have to be broadcasting over the big antenna at the station just as you're driving by. Our Sonata TPMS light will also blink if there is a police car within a couple of car lengths (waiting at a light, for example) and the car broadcasts. So I told her to ignore the TPMS light, or use it as a FuzzBuster instead of a low pressure warning.
 

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QUOTE (elp_jc @ Aug 24 2010, 11:42 PM) index.php?act=findpost&pid=351792
SEs are indeed 35 (you don't have that on your sig), but sensors are the same, so they go off around 30 psi.
How do you guys know the sensors go off around 30 psi? Something similar happened to me, so I checked the manual, and according to the manual, the warning light only comes on when the tire pressure is "significantly low".
 

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no sooner do you post this topic... my low tire pressure warning was on all day today, first time ever. checked the tires, even though i knew they were fine. two of them were at 35psi, the other two at 34psi. so either they arent set for 30 to go off, or mine needs some adjustment.

pulled out my little 12volt air pump and brought all 4 tires to 36, and the stupid thing finally turned off about 5 miles later.
 

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QUOTE (gregd71 @ Aug 25 2010, 07:16 PM) index.php?act=findpost&pid=351964
two of them were at 35psi, the other two at 34psi. so either they arent set for 30 to go off, or mine needs some adjustment.
There's no adjustment :grin:. You just need a better air pressure gauge. And remember to measure air pressure when COLD. Good luck.
 

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I think it is a known problem.

My tires were inflated to either 35 or 36 psi (I can't recall exactly) even though the door sticker says 33.

When I asked about this, I was told it was to keep the TPMS from going off.

I dropped them down to 33 and haven't had a problem so far.
 

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Woke up this morning and my low pressure light was on when i left for work (yes I had to work today!!!).

According to the documentation, the TPMS is supposed to set the low pressure indicator when the pressure drops more than 25% below the spec located on the drivers side B pillar (35 psi) OR a "sudden drop in pressure" (the rate of which is undefined). A couple of weeks ago it was ~110F here and this morning it was around 67F. So, I figured maybe the pressure dropped to low. When I checked, they were all around 30-31 psi. Although that's low, it's still well above the 25% threshold. I haven't had a chance to add some air, but I'm hoping the threshold is actually around 30 psi as others have described. I'll let you guys know how that works out.

I'm a bit paranoid because I have had horrible luck with the reliability of the TPMS on my Tahoe. The sensors just don't seem to last very long. The Tahoe actually has a self diagnostic/teach/reset routine built in that can be used to determine the problematic wheel, but it appears that the Sonata requires dealer intervention with some sort of a scanner. Not a good deal when I live over an hour from the nearest dealer. =(

EDIT: Setting all of the tires to ~33 psi did resolve the issue. So, either the HMA information is incorrect and the threshold is actually ~30 psi, or the accuracy of the sensors is very poor.
 

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QUOTE (DMLexpert @ Aug 23 2010, 08:30 PM) index.php?act=findpost&pid=351476
A quick Google search turned up lots of content about Hyundai TPMS being extremely sensitive to interference. So I checked the frequency used by that police department and found out that it is almost exactly half of the TPMS frequency used.
It will also blink when driving near the other police station closer to home. But not all the time. Apparently the missing link is that they have to be broadcasting over the big antenna at the station just as you're driving by. Our Sonata TPMS light will also blink if there is a police car within a couple of car lengths (waiting at a light, for example) and the car broadcasts. So I told her to ignore the TPMS light, or use it as a FuzzBuster instead of a low pressure warning.
RF interference is normal.. one dealer I was at got all the rentals from the airport store.. TPMS channel failures all the time. Seems to issue with .MIL installations, or other areas with monitoring/radio transmissions.

As of late, seems any strong close proximety RF broadcast will goof with the TPMS module. There is supposedly issues with phone chargers and NAV power cords emmitting some RF when the charge cord plugged into socket, in most cases they are located close to the TPMS module in the console, so signal from sensor may get fuzzy reception at module due to RF coming from the power cord..

Supposedly a dealer in WI has spent time on the issue, and has a survey form their TPMS customers fill out,, they supposedly have it narrowed down to specific phone cords and NAV cords that create the most problems, supposedly their warranty for TPMS claims is almost nothing, as it is appearantly customer induced.
 

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I have always found that low pressure is what sets off the indicators. Always, and without exception, I'll find something wrong, like a nail in the tire. Fix the problem and air them up properly and the indicators should go off. And I wouldn't trust a cheap tire pressure gauge either. You can't really tell by looking at the tire and the pencil type gauges are notoriously inaccurate. I like the round gauges and would go to a reputable auto supply store and get one. I'm not entirely certain of the quality of the gauges you find at discount stores even if they are of the round gauge variety. I'd air them up to about 36 psi cold and see if they go off. If not, then I would take them down to the recommended psi and take it to the dealer. They are definitely worth having because they have alerted me to two tires going flat from nails and I didn't know it nor could I see from looking at the tire from the outside.
 

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New Owner here. Sonata 2011 SE. I've had the car about 1 1/2 months and checked the tires as soon as I bought it (got a new ACURA TL a decade ago which was deliverd with 42 PSI in the tires)...........

Temp's have dropped from low 80's to mid-50's here in Ohio. I got my first low pressure indicator on the way home from work today as soon as I started the car. I thought crap, I got something in a tire. Got out and visually inspected them. They all looked fine. No warning light going into work (Sonata is garaged and the outside temp was in the mid-60's in the garage).

I expected the indicator to go off on the way home, when the tires heated up, but nope, it stayed on. When I got home, I checked all four tires and they had lost pressure due to temp change, but were all around 33 PSI hot. I inflated them to 35 1/2 PSI and will see what the sensor reports tomorrow morning.

One of the comments in this thread was about the sensors coming on due to a big "rate of change". I'm thinking along the same lines.
 

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I'd check the cold air pressure in the morning with an accurate tire pressure gauge. I am inclined to agree with the sudden temperature theory. I had the same thing happen in a Ford product one time and the service department had all kinds of complaints that came in at one time, more or less ruling out the occasional nail in the tire.
 

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There's nothing 'sudden' about it folks. Tires seep air all the time, to the tune of about 1 psi per month. And temperature changes drop pressure as well, to the tune of 1 psi for every 10ºF ambient temperature difference. If the last time you checked your tire pressures was 3 months ago, they're about 7 psi low by now. Sensors trip at around 30 psi. You should check your tire pressures more often, especially when temperatures are declining. And you need to drive a few miles after airing tires up for warning light to go out. Hope this helps.
 
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