Best way to hide TPMS warning light?

What's the best way to cover up the TPMS warning light on the dash? A bit of electrical tape would work but it seems likely to gunk up the surface. As I understand it there is no way to permanently disable the circuit with TechStream.

That light is now lit because apparently one of the sensor batteries died. It is a 2007, and if all the sensors are original they were living on borrowed time. The dealer wanted my left nut just for a diagnostic, and the tire shop we usually use asks $123 to fix one and $87 more for any others. The thing is, I have this magic tool called a "pressure gauge" which is employed periodically, and I also am in the habit of walking around the cars to check the tires by eye, so I'm not at all worried about a slow leak. I suppose the TPMS might provide a few extra seconds warning if we ran over a nail on the highway, but other than that, it doesn't have much value. Certainly not the ~$400 it would cost to change the sensors on all 4 tires, because if I just do the one, another may very well go next month.

 

Yeah, I saw those on RockAuto. I don't know yet if any of the software I have can talk to the TPMS. In the meantime I called a couple of other shops and they were all very close to $120 to replace one sensor (they supply the sensor and program.) Kind of ridiculous that this sensor costs roughly as much to replace as a tire. One might have thought they could design a sensor that screws onto a shorter stem, with the weight landing on the rim. Basically just an electronic pressure gauge that can stay on the car. Then changing it would be roughly as difficult as changing the cap.

Duh, of course they have:

 

The cap ones are interesting but I do wonder about the forces. The sensors can't weigh much, but once the tire is rotating at 700 RPM (about right for highway speed) that will apply some force to the valve stem and the tire as a whole. Perhaps the latter isn't enough to unbalance the tire significantly, but I suspect that stems in general, and those on the internal TPMS systems in particular, are not designed for any type of load at all (caps weigh nothing.) Also, if one uses the little lock nuts that come with these then adjusting tire pressure becomes a minor PITA. At least it is trivial and cheap to change the batteries on them, as they use CR1632 batteries and the two halves unscrew. Also the displays on these cheap units show much more information than do any of the car TPMS systems I have seen.

Wouldn't it be wonderful if the little cap units were compatible with the Prius's system?
It seems wildly unlikely though.

 

The TPMS started working again. Coincidence, miracle? Don't think so, see details here:

No air out of defrost vents at windshield | PriusChat

 

Sounds like a new and creative way to throw money down the drain.

Not by me. I was never motivated to fix this problem because for all practical purposes nothing was broken - the tire pressure is checked periodically in any case, TPMS or no TPMS. It would have been nice if the Prius's MFD was able to display the tire pressures, eliminating the (oh so slight) burden of having to carry a tire pressure gauge. I would have missed that convenience and might have spent some time trying to figure out the issue.

 

Had a little time on my hands today and decided to see what Techstream actually showed for the TPMS system. The one I use runs in VirtualBox and I have not figured out yet how to get a screenshot out of that. This Techstream worked correctly with my mother's Gen 3, showing that one tire was low, and the various data fields were all filled in. Anyway, on our 2007 Techstream clearly talks to the TPMS computer since it sees the ID values, but it doesn't look like the TPMS computer is talking to any of the sensors. Either that or all of them now have dead batteries. The data list said:

Mode start: Normal
Main Tire: 4
2nd Tire: 4
Select Switch: Main
Vehicle Speed: 0 MPH
Registered ID1: A7CF1D2
Registered ID2: A6F91D2
Registered ID3: 3CAF1D5
Registered ID4: 3C081D5
Registered ID5: 000000
ID transmission Status: Finish
Initialization Switch: OFF
ID1 Tire inflation Pressure: N/A (ditto ID2-ID5)
ID1 Temperature in Tire: -40F (ditto ID2-ID5)
ID1 Battery Voltage: Over (ditto ID2-ID5)
Select SW Info: without
Initialization SW info: with
Threshold Low: 26.5
ID1 Initial Threshold of Low Pressure: N/A (ditto ID2-ID5)
Number of DTC: 5

Additionally asking for trouble codes or utility->signal check -> one signal check
both gave error 0x91020324.

Since we can talk to the TPMS computer, and the TPMS computer cannot talk to the sensors, maybe the antenna is not plugged in (or completely missing)? Where is that connection?

Edit: forgot to mention, scanned the whole car for DTCs and it only gave the spurious light sensor in the dash one. So I don't know what the "Number of DTC" line is about.

 

Is there a way to distinguish with Techstream "all 4 TPMS sensors are dead" from "cable to receiver is not plugged in" or "receiver has failed"?

The screen shot doesn't show the DTC field. Mine said "5" and according to the TW part of the manual that is the count of stored DTCs. But the ECU didn't report any failures to Techstream. If all 4 were dead, shouldn't there have been C2111 through C2114? Did the car for the screen shot show a C2112 code?

Apparently the receiver signal is on the one cable going into the ECU, so it isn't possible to leave that unplugged at the ECU without taking the whole thing off line.

 

So how do tire shops set these sensors up if they go to sleep on cars which aren't moving? Do they perhaps respond to a "wake up" signal from the programming devices, or the car itself? There is something similar to that in network computing, where "Wake on Lan" packets cause computers to come out of a low power state and boot.

When I read the TPMS values on my mother's 3rd generation it had not been driven in quite a while. Probably it was showing the last valid readings it had received.