Lessons from the spare

[yxmj]

So I have a new to me Dakota pickup. Nice truck, but from day one the low-pressure indicator was lit.

I followed the manual and every post I could find on the inter-web to clear it but it would not go out, finally I just broke down and bough a new set (4) of sensors off Amazon.

 

I had planned on getting a new set of rims and bigger tires soon, so I set the sensors aside to use on the new set.

Last week I pulled a trailer up to a remote cabin I have. The last hour of road is a bit sketchy so I wanted to be prepared. The truck has a fuul sized spare on a matching rim under the box Like my MJ. Wanting to prevent the laying in the dirt and fighting to get the spare out in the event of a flat I took it out and placed both the trailer spare and the truck spare in the box…..making sure to air them both up to proper pressure for the trip.

 

About 20 miles into my ride I passed a radar trap…..I glanced down to check my speed….right then the pressor sensor indicator went out…..hasn’t gone on since.

 

Are you f-bombing telling me it was the pressure in the spare the whole time???????

[89 MJ]

Not going to lie, that's hilarious. Why not take an MJ though?

[Pete M]

my 06 Liberty used to know which one was the spare, no matter which rim was actually there.    I mean, those sensors are all long gone now since swapping out the rims, but it used to.

[Torq_Shep]

My 07 Odyssey TPMS light has been on for 20k miles. No idea why. Don't care =P

[89 MJ]

My MJ does not have a TPMS light on the dash. 

[fiatslug87]

That happened with my wife's FJ Cruiser, light was on, I aired up the 4 tires, light would not reset, then I realized I did not checked the spare which is under a cover and has another plate that needs removal. 

[ComancheKid45]

3 hours ago, 89 MJ said:

My MJ does not have a TPMS light on the dash. 

 

 

Nope, I don't have this problem either. Haha

[gogmorgo]

That’s interesting. I’ve seen the spare pressure option on the scan tool when relearning sensor positions, but never encountered one with a sensor in the spare.

I always liked that the Dodged could figure out that you rotated your tires on their own. Chevs learn specific sensors to specific positions, which means if you rotate them without relearning, then you get the truck back in the shop one day because the truck says the front left is low even though it’s way over pressure, meanwhile the rear right has 5psi in it.

 What’s crazier than the spare having a pressure sensor in it, is that newer Subarus know their tires are low without even having pressure sensors. If the steering angle sensor says it’s pointed in a straight line, but one of the wheel speeds is consistently different than the others, it knows there’s an issue and triggers the light.

[scguy]

Newer Honda's also use what's called indirect TPMS, based on wheel speed. GMs in the early 2000s used a much cruder version. My 2001 Alero (bleh) had this, and the reset button was in the fuse box. 

 

My 02 WJ Limited had a spare tire sensor, and knew which was the spare, also. It would flag Spare Tire Pressure Low. It also had automatic wipers, something I miss and don't see on many new cars. 

[dasbulliwagen]

On late model Chrysler vehicles, it only got a sensor in the spare if it had a full size matching spare, which is fairly rare, but was an upscale option on some. This includes 07 up wranglers with TPMS.