TPMS Warning When Headlights on - III w/Nav

What are your tire pressures? They could be low, and turning on the lights is just a proxy for lower temperature. The same amount of air will have a lower pressure when the temperature is lower. Not much, but enough to trigger a marginal situation.

 

When my TPMS light came one, I got out my pressure gauge and checked my tires. One was low. I guess that's what the TPMS light means.

Have you checked your tire pressure? Seems like an obvious question, but it seems like 90% of people who ask TPMS related questions haven't bothered to check.

 

I have the same problem - however it only occurs at random - and not always after 30 minutes. I've been to the dealer 5 times and even had Toyota corporate get involved. Still not fixed . I wonder if it does have something to do with the LED's because I have also done the all LED mod from superbightleds.com Who knows.. However I have made a thread from the start of my issue, and all the way up to today. If you have time, give it a read over.

http://priuschat.com/forums/gen-iii...-tire-pressure-warning-light-dead-sensor.html

 

If the tire pressure is low the light just comes on.

If it blinks for 1 minute then stays solid that indicates a malfunction.

I bet something about your LED lights is preventing the receiver (which is in the hatch area) from picking up the radio signal from the wheel sensors. The dealer can pull the codes for you which will tell you exactly why the light is coming on.

It takes about 20 minutes of not getting any signals from the tire pressure sensors before an error is triggered.

Perhaps some of your LED lights are using pulse width modulation (like the ones in the rear light assembly) that is causing interference. Try switching the rear exterior lights back to bulbs and see if that helps.

The dealer can run tests .... but you might get charged especially since you swapped out all the bulbs and the problem coincides. If you put everything back to regular bulb and you still have the issue, they will have to fix it.

 

May just be a coincidence and you're TPMS ECU is failing just like the Chicken's! I'll be following this thread closely because I'm getting ready to do the DRL Mod, which will have my front turn signals on when ever the car is on, so I want to replace those bulbs with LEDs to prevent heat build-up from damaging the turn signal housing or lense. Hopefully there is no real link between the use of LEDs and the TPMS failures...

 

Did the dealer hook up your car to pull the TPMS IDs and what they were registering? The TPMS ECU holds its own DTCs. I just went to the dealer to figure out why my light was doing the same thing.

Here's some background on my recent (march or so til yesterday) fun with the TPMS. I had my winter wheels & tires on my Prius w/ those TPMS IDs programmed into the ECU. When I swapped the summer set onto the car, the Firestone dealer was unable to update the ECU (they don't have the software and cable) but they give me the summer TPMS IDs. As I drove over the next month or so, the TPMS light would do exactly what yours did, until it started doing it everytime I started the car. In other words, sometimes it would do it and sometimes it wouldn't. I think it depended on how close I parked to the garage and whether or not it happened to pick up the transmission from the winter set at the time. Over the summer, I got the ATEQ TPMS QuickSet tool to update the TPMS IDs. I did that based upon what the Firestone told me, but it didn't fix the problem. I purchased a TIS compatible cable online, paid for a 2day subscription to Techstream TIS, and looked at what was programmed. 3 of the 4 sensors were reading 35.x PSI (so, it reads to the tenths, for those wondering) and one was a negative number. Ok, I take that as it's not working or not correct. I confirmed all of the IDs were exactly what I had recorded on my piece of paper. I ended up at the Toyota dealership yesterday, and they pulled the information and determined that the 4th ID was incorrect. They updated it, cleared the DTC (I had already cleared one when I was using TIS last week) and now I'm good to go. I've used the QuickSet tool to pull the correct IDs (they didn't give me that paper, and I forgot to ask).

I think the dealer should be able to tell you what the IDs are, what they are reading, and if one of them is dead. This should be covered under the factory warranty. Tell them you want the Techstream printout showing what the IDs are and what their readings are! For that light to flash for 60 seconds then stay on, indicates some issue with the TPMS IDs, either the sensor is bad or something is incorrectly programmed. When this happens, it will throw a DTC and it will need cleared out also. Maybe they just forgot to clear the DTC.

Hope that rambling of a message helps!

 

Ya, but his system works perfectly while driving with the lights turned off and about 20 minutes after turning on the lights the TPMS error comes on. The service manual said it takes exactly that much time of not picking up the sensors before the lights comes on. (Flashing for 1 minute then solid.)

I would try reverting back to the stock running light bulbs .. first try the back ones then the front.

Also, did you change the license plate frame lights?

The 12v lighting system is unrelated but the TPMS receiver is in the back and maybe it is sharing a 12v or ground line with the lights and the LED's are funking it up.

Should be 30 minutes to change those back, no?

 

Several people, including myself (i've only done parking lights for now), have replaced some of the bulbs with LEDs and not experienced a problem with TPMS interference. I'd be quite surprised if the LEDs were causing the problem, although I won't rule it out.

I can't remember what the DTC was for my TPMS, but once it logged, the TPMS malfunction indicator light came on every time I started the car. I did tell it to record this information before I cleared it, so maybe I can find the log file on my laptop at home.

It could be the ECU, a battery that's starting to die in one of the TPMS, or the TPMS receiver itself.

It's too bad you can be hooked into a computer with Techstream when the light is off, and see what the TPMS ECU is reading. Then when the lights come on and 20 mins later when the malfunction indicator comes in, see what the changes are and what the DTC says.

 

Ya ... I certainly wouldn't think the LEDs could cause a problem either ..... but maybe some are using pulse width modulation to extend their life and that frequency modulation is causing interference, etc. The way to be sure is to just remove them and see if the problem goes away. Process of elimination.......

Could be swapping back to bulbs still causes a problem when in that case a trip to the dealer is needed.

Or just go behind the glove box and just unplug the TPMS ECU to disable the system and light.

 

Agreed with the troubleshooting method. If the only change has been the LEDs, the first step is to revert back to the original setup. If that doesn't solve it, then a trip to the dealer is definitely in place. And hopefully a note to the group here as to which bulbs they were that caused the problem.

I wonder what frequency the LED modulation would use. If I recall, aren't the TPMS around the 315 MHz range?

 

Good question, but I don't know. I wouldn't think it should interfere at all -- but perhaps it's noise on the 12v line.

My Samsung LN52A650 TV (52" LCD) interferes with my IR remotes when I first turn it on and the backlight output is low while warming up (or I set the backlight to the lowest setting.) Apparently the backlight driver uses a similar frequency to IR remote controls and I guess the CCFLs put out some IR.... When it warms up and the backlight is set to my normal 4 (out of 10) there is no longer an issue.

Samsung had a fix which was replacing the driver with a newer revision but I didn't bother as it was such a minor problem. I just have to point the remotes directly at the receiver ..... If anyone uses Tivo, you know you can pretty much point the remote any direction. Just not while the TV is warming up, LOL.

Anyway, just shows that sometimes you can get interference in places you don't expect it.

 

Seems the bulbs have a wide operating range -- 9v to 18v .. that may mean they do use pulse width modulation and an inverter to control output intensity... this means they could possibly generate interference.

I would try switching them out.... I would go back to stock bulbs all at once. Test for a week to see if there is a problem. Then start installing them back in one by one. Try switching out the license plate bulbs. Then side marker. Etc.

 

I think a lot of the LED bulbs have a wide operating range to help compensate for voltage fluctuations.

I vaguely recall a few others using similar or the same bulbs in their cars as well, and don't seem to see that many TPMS problems. Although, it's very possible that it's a bulb anomaly also.

I didn't realize that you'd replaced so many with LEDs already. I was thinking there was only a couple exterior ones, and that it wouldn't be much work to swap them all back.

Sorry if it's been asked already, but have you had the dealer look at the DTCs from the TPMS ECU yet? What did they say? If that light is coming on randomly (as it seems may be the case), the ECU should have stored an "old" DTC. Despite changing the bulbs to LEDs, the dealer should hook it up for free under the factory warranty. IF, they found the LEDs to be the cause (doubtful they could correlate them together, knowing most dealers) then they would probably charge you. Just tell them that the TPMS light has been blinking and staying solid sporadically. Tell them you want a printout of the DTC page from the TPMS ECU - this way you can confirm for yourself if there was anything. Well, that's assuming they don't try to flim-flam you and clear it out then print it.

This may be a better option than spending all that time to change the bulbs back and try to troubleshoot that way.

Just throwing another option out there for you! If you were closer to DE and I had a full year subscription to TechStream, I'd offer to hook it up for you. Unfortunately, it's $55 for a 2 day subscription and MI is roughly 10-13 hours from me (I used to have friends in Boyne City, so made the drive a few times).