Low Tire Warning Light Malfunction in Cold Weather???

[AGuyNamedSteve]

We just took a drive in our 2006 Solara (SE 4 cyl) from Seattle to central Arizona. When we went through the Siskiyous Friday night and Saturday morning, the Low Tire Warning Light went on. It was time to get gas anyhow, so we stopped at a station and checked the tires. The lowest had 30lbs and the highest had 34lbs on our gauge. I hit the reset button and off we went.

It came back on about 30 minutes later. Temps in the pass were in the low 20s - low 30's. We drove with it on into Yreka, CA where we stopped for the night. The next morning we reset the light and took off again. About 30 minutes into the ride the light came on again. It was below freezing at this point. We drove with it on for a while. The next time we gassed up, I reset the light and checked the tire pressure with a different gauge. All pressures were still above 30lbs. The light was reset and it didn't come on again.

The recommendation is 29lbs (cold) for the 215-60-16 tires. The first time we checked, even though the temps were cold, the tire pressure was above 30lbs. I understand that cold weather brings temps down in tires, but that doesn't appear to be the case.

The only other variable I can figure is that the light only came on in temperatures below freezing. So I'm wondering if there has been any history of this happening, maybe because of a sensor failure in cold temperatures???

Any thoughts?

[Gadgetjq]

Steve,

You don't say whether that 30 pound pressure and 34 pound pressure are on the same axle. If so here's a thought.

The system 'might' have been reset with both tires at the same pressure 'but' remember all tire pressures will go up while you're driving. In extended highway running you can easily pick up 5 pounds (which is why you're always supposed to air up tires when cold).

If both tires were aired up at 30 pounds when the system was reset and if one has a slow leak it could account for the pressure difference you're seeing when the tires are hot.

If you're just pushing the button until the light goes off you aren't actually resetting the system, you're just turning the light off.

So, what to do. When the tires are cold set them to whatever pressure you prefer (usually exactly the same for both on the same axle). Now reset the reporting system properly by holding the button in until the light blinks several times. Be sure and check that tire with the lower pressure in case you do have a leak.

Cheers

[AGuyNamedSteve]

Thanks Gadgetjq,

Those are some thoughts. There's nothing in the manual to say how 'intelligent' that system is. It's only referred to as a low pressure warning light. My first thought is that the sensor measures tire pressure (on a per tire basis) and reports when tire pressure reaches a certain minimum (i.e. light on at 25lbs in any tire, regardless of neighboring tires). But I don't know.

The 30lbs in the one tire was while 'hot'. Of course that's as hot as the tire would be after driving for the past several hours where the last hour was in temps in the 20's.

My wife has the car out now. I may have to check it before it gets too late as where we're staying the next couple of nights has temps in the 20's at night and 50's during the day.

Then I'll go through the reset procedure and see where we are. Our schedule has us going through that same mountain pass early next week.

[Gadgetjq]

Steve,

I'm not certain when Toyota switched over to a system that actually reads tire pressure but suspect it's the '07 and later.

The earlier system uses the anti lock brake sensors to determine whether there's a difference in wheel speed from one side of the axle to the other. If pressure on one side drops a couple of pounds the diameter of the tire is reduced so spins faster than the fully inflated side. Result, the light comes on telling you there's been a pressure loss in at least one corner.

I 'think' (a gen 2.5 owner will have to confirm or shoot this one down) the later model actually tells you which tire is losing pressure.

Cheers

[MCOjerry]

But he has a gen 2, not a 2.5.

Maybe the temperature change was just affecting the tire pressure oddly.

Is it working properly now that you are home?

[AGuyNamedSteve]

We're not home yet - just made it half way on our round trip.

From Dewey, AZ to Albuquerque, NM we cruised consistently at 80mph on I40 and it didn't come on once. Temps were around the high 30's. After having an early dinner in ABQ we hit the road at 6:00 east on I40 which hits some pretty cold areas. When it hit 27*, the light came on again. We continued to Santa Rosa where the temp was 29*. We did the full reset (hold button until it blinked) there. It didn't come on again after that, and the temp at our destination in Portales, NM was 20* last night.

I really don't know what to make of it, but it sounds like the ABS thing could be part of it as there has been a slight difference between left and right rear. The fronts have been the same the entire time.

[Gadgetjq]

it sounds like the ABS thing could be part of it as there has been a slight difference between left and right rear. The fronts have been the same the entire time.

That would certainly be the reason the light came on. The system was probably calibrated with 30 pounds (or whatever) on both sides. When one rear tire fell to 26 pounds the light came on to warn you to air it up.

If you've reset the system without adding air to that tire (for whatever reason) the car now thinks it's normal to have 30 pounds on one side, 26 on the other so when you get around to adding air to the low side the light is going to come on again.

Cheers

[AGuyNamedSteve]

Actually the low tire (right rear) has never been down to 26 lbs. The lowest it has ever been is 30. But it has been 1-2 lbs less than the other rear tire.

I'll just keep an eye on it as we'll be heading back home starting Saturday. We're taking the same route we used to get here, which should send us into some low 20's temps again.

Thanks for the ideas and information!