tpms light came on

How smart is the light, and how smart is the dealer?

(don't even ask how smart is the driver ok)

New Accord EX4 sedan about four months out of the dealer, haven't done a thing yet but put gas in it and putter around town. Noticed the TPMS light on, pulled over to look at the tires. Nothing obvious, so I drove on. Next time, I looked carefully, maybe the right front was a tad low?

Drove on down to the service station air pump, promised to buy some gas if they'd turn on the coin-op air. Turns out that, warm, all four tires were almost exactly 28psi. But my door panel suggests they should be 32psi cold. Harump. I know my dealer has long had a habit of underinflating when they adjust tires, why, I don't know. And I've beem wondering why my MPG was a mile or two lower than on previous Accords. Harump. So I blew them all up to about 32psi warm. Turned the key, drove a block - light stayed on. Maybe a bad sensor, huh?

Had lunch, got back in - and now the light was off.

So, does it take a couple of samples to convince itself that the pressure is OK? How the heck does the sensor work anyway?

Just wondering.

J.

Reply to
JRStern
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Did you check the pressure of the spare?

Reply to
JRE

Didja ever READ the OWNER'S MANUAL about that little light?

And no, your eyeball is NOT an air pressure gauge.

Oh, I dunno. What does your OWNER'S MANUAL for your SHINY NEW $25,000 TOY say?

Reply to
Elmo P. Shagnasty

My TPMS light will come on occasionally on my 08 EXL V6 when the temperature drops to -35 or -40 and once it warms up to a balmy -20 the light goes out. I was thinking of having nitration put in and see if that would make a difference. just a thought

Cheers

Reply to
Curly

Er, yeah. Well, out here in Los Angeles, I suppose when the Richter

8.0 hits it's likely to cause the TPMS light to come on, too. I'll let you know.

J.

Reply to
JRStern

Speak for yourself.

You're not going to fool me like that, I know how that worked out at the end of Raiders of the Lost Ark!

OK, I understand there's some federal mandate that we have these things, and I guess they work by emitting deadly radiation and reporting my whereabouts to the FBI at every moment. Just as in five years, we'll have the same devices rammed up our asses for Obamacare.

But I was just wondering (a) why the light didn't go out right away, that is still lit up the next time I started and drove a few feet, and (b) why my dealer doesn't ever open up the users manual or read the plaque inside the driver's door giving recommended pressures.

.. and I'll see if I get back that 1-2mpg now that the pressure is up where it ought to be.

J.

Reply to
JRStern

So your eyeball can tell the difference between 35psi and 32psi?

SURE it can.

Reply to
Elmo P. Shagnasty

hmmmmm, what does your OWNER'S MANUAL say?

Excellent question. Ask him.

Reply to
Elmo P. Shagnasty

JRStern wrote in news: snipped-for-privacy@4ax.com:

The TPMS will sample tire rotations once the car's speed is over

30 mph for about a minute. If it likes what it sees, it will then turn the light off.

Some tips:

  • Use a hand-held gauge (NOT the one on the air pump), and use the same gauge for all the tires.
  • Check and set the pressures COLD and OUT OF THE SUN. First thing in the morning before the sun hits the tires is best. If you must add air when the tires are warm, set the pressures TOO HIGH, then bleed off some air the next morning to arrive at the final pressures.
  • An ordinary bicyle pump is great for fine-tuning the pressures a pound or two at a time.
  • Inspection by eye is NOT reliable; tires will only be obviously visually low once they're down to about half their proper pressures.

Another important tip: Occasionally, one tire will "settle" to a final rolling circumference that is different from the others. This can cause sufficient rotational differential from the other tires that can fool ABS- based TPMSs into thinking that tire is low. You can check this by carefully measuring the distance from the ground to the top of the wheel rim on each of the two tires on an axle. This must be done with the car on a perfectly flat surface, such as the concrete pad of a gas station.

Reply to
Tegger

I F***ING KNEW IT! THANKS, BRO!

One word - prepare!

Reply to
Tony Harding

Could we possibly make tire pressure any more complicated? These tpms' are bs.

Reply to
diogenes

diogenes wrote in news:hp9q93$d3j$ snipped-for-privacy@speranza.aioe.org:

Write your Congressman. Congress is who imposed it in the first place.

Reply to
Tegger

Thanks, Tegger.

I gathered from my experience that some speed or distance is necessary. I wonder at the devices, do they need the rotation to generate the power to send a signal? Yet the web page for the manufacturer suggests they have a device that queries them at rest. I still don't know how they get the signal to the dashboard, some form of RF I guess, bluetooth or some other frequency.

Yes, I do.

Good idea. I knew I should have put another pound or two in, to guestimate the right numbers "warm".

Ha. Takes a fair amount of pumping a hand-pump to move a car tire

1psi, and the connections often leak just about that fast.

Sure, but I assumed that three tires were good and one was lighting a sensor, and you'd think that might be visible. In my case they were all just about equally low so there was no real visible difference.

I don't grok this, why would rotational difference set off a pressure sensor, do these things cross-check each other? I can't figure why that would help.

So, do the dealers have a lot of customers with these kinds of issues?

When I next bring this car in for service, I'm going to mention the low pressure to the service manager and the front office. The only way the four wheels had the same low pressure, is if that's how they gave it to me. I do recall in the past, some guy at the dealership said they ran them low because "it gave a smoother ride". Guess he's still working there. Can't be good for the tires.

J.

Reply to
JRStern

I'll add it to my airbag letter.

J.

Reply to
JRStern

But good for the bottom line (selling new tires). BTW, I suspect lots of owners appreciate the "smoother" ride.

Reply to
Tony Harding

JRStern wrote in news: snipped-for-privacy@4ax.com:

There are two kinds of TPMS. One is ABS-based (rubber valve stem), and the other is transponder-based (steel valve stem).

Transponders are incorporated into the valve stem. They work a bit like cell phones, in that they have batteries and emit a radio signal. That signal is received by the TPMS computer. Eventually, transponder batteries will go dead and need replacing. Draw on the batteries is tiny, so it will be years before they go dead. But when they do, imagine all those irate customers! Thank you, Congress.

ABS-based requires actual tire rotation to determine if one tire is low. Transponder-based does not require tire rotation. As I understand it, transponder-based systems wait a bit before deciding that there's a problem, even though they /could/ snitch immediately if they wanted to. I'm not sure why.

My Schwinn pump does about six pumps to the pound. I consider it cardiovascular exercise.

There is no appreciable leakage from the valve stem when the pump is connected to it.

Nope. No obvious visual difference until they're about 15psi low.

Rotational difference is used on ABS-based systems. ABS-based systems do not have sensors inside of each tire. Measuring and comparing rotations is the only way they have of being able to tell if a tire is low.

Transponder-based systems measure tire pressure directly, using sensors inside of each tire (and sometimes even inside the spare).

Yes. Just like EVAP.

If he said that, then he's a dummy.

Probably not. But this monkey is not too smart if he thinks he's smarter than the Honda engineers that designed your car. I'd trust the Honda guys before I trusted some goofball working for a dealership.

Reply to
Tegger

Must disagree. I can't tell pressure on some arbitrary tire on an arbitrary car, but I can get used to what my own tires look like properly inflated, and notice a different curve as they get low. I've had to deal with leaky tires before and had practice.

OK, I see. Sort of. Funky.

I think the logic is that Honda has to overinflate them to get the EPA mileage up, but that for a mile a gallon or two, you can get a better ride with lower inflation.

Might even be somewhat true, but even so, they overdid it.

J.

Reply to
JRStern

Thus spake "Elmo P. Shagnasty" :

Mine can. There's this little LCD that I look at.

Erh, wait, that's what you were talking about using.

I can tell the difference beween 32 psi and 24 psi.

Reply to
Dillon Pyron

Thus spake Tony Harding :

There's going to be a run on KY. And Astroglide. And probably 30 wt.

Reply to
Dillon Pyron

Thus spake snipped-for-privacy@home.ca :

I know you're talking C and not F. Oh, that's still fracking cold.

Mine will usually come on around 20F if the pressure is near the trigger point. Sometimes I can warm the tires a little (if you've seen any kind of auto race, you know how).

BTW, my light came on yesterday. Since it hit about 70F, I don't think it's the temperature. But I'm waiting until this morning when they're cold to air up.

Reply to
Dillon Pyron

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