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Tire Pressure Warning Light

81K views 24 replies 17 participants last post by  Fibber2 
#1 ·
Just had the first 7500 mile service on my new 2013 Outback. It has Continental tires that do not appear to be unidirectional. This service includes rotation, which was done. After about an hour of driving back from the dealer, the tpms warning light came on. We stopped and checked the pressure, but everything was ok (but tires were hot, of course). Next morning, checked cold tires and everything was ok. Tire pressure is supposed to be 32 in back and 30 in front. The light is still on.

The dealer who did the service told us to raise the pressure 4 or 5 points and drive around the block. He said that's what they do when the light won't go off and that we should keep the tires at the higher psi. That doesn't seem right. We're going to try it, then put the tires back to the recommended pressure for the tires we have.

Any ideas? We did come through a torrential rainstorm right before the light came on, if that means anything.
 
#3 ·
The sensors are just dumb devices all they have is a minimum set pressure once that is triggered the light goes on. Things that can impact that are cold over night temps and the tire pressure being on the lower side of the required pressure. Also keep in mind that the pressure gauge your using could be less than accurate also. I have like 4 guages floating around the garage and out of curiosity I checked all of them on the same tire back to back. They covered a range of 15psi difference between all of them.

So putting 4 more lbs of pressure in your tires according to your gauge may simply bring the tires right to the bottom edge of the TPMS sensor setting and turn the light off. Very cold over night temps really seem to make the sensors unhappy also.
 
#4 ·
Usually if a sensor fails, the light will flash at least for a time (see the section in the Owners Manual); if the light does not flash and is on continuously, then at least one of the sensors is at a pressure below the low threshold (which I believe is 26 psi), or there's another type of malfunction.

When tires are rotated, it's not uncommon for the tires to be dropped down after the lug nuts are removed and they're then bounced around as they're moved to the next position. It's possible that a sensor was damaged such that it is still working, but misreading the pressure.

The dealer Subaru Select Monitor III can be used to identify what each sensor is doing -- whether it's working or not, and the pressure signal it's sending to the TPMS control module. That would isolate the cause that's triggering the light.

Did the dealer check the pressures in each tire, or was the recommendation to increase the pressure made by phone? If the dealer checks the tires and they are okay according to their own gauges, then there is no reason to have to increase the pressure. Rather, it indicates a problem and that should be covered by the warranty.
 
#6 ·
Thanks for the responses.

The reason I thought it was 30 front, 32 rear, is that that is what the gauge (it's a really good quality one) read. Upping the pressure turned the light off, but what we think happened is that the dealer rotated the tires and did not check and redo the pressure - that's why the readings were reversed, back to front. Upping the pressure was recommended by phone, but we are 2 hours from a dealer, so we're trying to avoid going back there. We are reducing the pressure to the recommendation in the manual and we'll see if the light comes back on. If it does, we'll have to take it in.

Again thank you. This forum is great.
 
#7 ·
Thanks for the responses.

The reason I thought it was 30 front, 32 rear, is that that is what the gauge (it's a really good quality one) read. Upping the pressure turned the light off, but what we think happened is that the dealer rotated the tires and did not check and redo the pressure - that's why the readings were reversed, back to front. Upping the pressure was recommended by phone, but we are 2 hours from a dealer, so we're trying to avoid going back there. We are reducing the pressure to the recommendation in the manual and we'll see if the light comes back on. If it does, we'll have to take it in.

Again thank you. This forum is great.

If it does come back on, before taking it back in, try this:

Under inflate all 4 tires by a couple of psi. Drive the car for at least 20 minutes. Re-inflate to normal pressure.

Also, make sure you're checking the tires before you drive it for the day. Even a 1/2 mile trip to the gas station will heat them up enough to change your readings.
 
#8 ·
34-35 lbs of tire pressure will not hurt anything if the tires are 30-32 cold with your gauge putting a few lbs more in them will not hurt anything and as I pointed out will help the sensors sort it out. Dropping the pressure will simply keep the light on. The sensor only trip the light when the pressure is low - not when it is high.

Also the sensors do not know which tires are on the front or the back! All they do is trip the light when the pressure drops below a certain point. I think mine tripped the light in two cases - cold overnight temps when the tires were around 30lbs and during warm temps when the tires dropped into the 25lbs range
 
#21 ·
No TPMS is compact temporary spare tires. Only on tires that can enter the rotation scheme. Yet in a strange way, that's somewhat counter productive. Ever see someone put on their 3+ year old temporary spare, only to find it's basically flat from neglect?
 
#22 ·
Had the TPMS alarm on my 2012 outback.

IT was a very small nail and a very slow leak. I am sure the TPMS may have saved a tire from destruction.

I have had a TPMS system save two tires on my 5th wheel and one on my 2500 HD pickup. One was a nail, one was a 3/8 x 2 inch bolt and the third was a crack in a valve stem. All three were slow leakers that may not have been caught in time to prevent a tire failure.

What did we do before TPMS we destroyed tires from nails that were picked up on the highway.
 
#23 ·
+1

Wife lost a tire due to a debris slice on the Interstate, but the TPMS light alerted her to the deflating tire and at least saved the rim. She watched it fully deflate while standing on the shoulder of the road. What if she hadn't had that less than a minute notice in which to react?
 
#24 ·
My 2016 Outback's TPMS light came on last night. Temperatures were probably in the high 20's F. Checked the four tires and all were at 32 psi. Slightly low from the 35 Front, 33 Rear (I think that's right) as noted on the placard on the door frame.

Pumped them up to about 36 all around.

Light stayed on.

When I got home, I pulled the spare, which is a full size temporary spare. It was at 50 psi. Should be at 60. I pumped it to 62 psi.

Light stayed on.

Drove to dealer next morning, about a five mile drive. Somewhere between home and dealer, the light went off.

I haven't found in the manual where there is a certain distance or time one must drive to reset the TPMS after "fixing" the problem.

Also, whether or not the spare tire has a sensor? I really don't know.

Why wouldn't it have a sensor?

Wonder after the Ford Exploder fiasco if the laws dictated low pressure sensors for the four tires, or the spare, too, if so equipped?

Ray
 
#25 ·
Temporary spare tires (the 60 psi variety) do NOT have a TPMS sensor, and unless something has changed, I don't believe that you can upload any more than 4 sensor ID codes to the system at a time. Some vehicles that come with matching full size spare tires (like a light truck) will have a total of 5 sensors, and their systems are smart enough to know that any 4 could be in use at a time.

So your spare wasn't the issue.

Now I'm going to assume that you pocket pressure gauge is accurate in the cold, and the pressures you read out, and topped off to are correct! More than one person has been fooled by this on a cold day.

You could have a bad sensor. It happens. My old Toyota van had one. Or the on-board receiver & computer had a brain fart in the cold.

There are situations in which sensors won't properly transmit, or the reception is blocked by interference. In this case, your light can come on as a result of "sustained loss of signal", and not because of the pressure.

The situation usually self corrects once the tires are topped off and the sensors stop screaming and report happy news. But it can take a few miles, especially if you are doing low speeds and the sensors occasionally nod off to sleep.

I think the net here is see if it happens again, see your dealer.
 
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