TPMS ( Tire Pressure Monitor System ) Problem

TheForce · 07-19-2007, 10:19 PM

I'm having an issue with my TPMS light on the dash. It keeps coming on after I reset it and I have good air pressure. I drove all the way to hybridfest with this issue. This happened before about a week ago after I installed my PC. This was also just after I topped off the tires to 44,42. I thought maybe I just needed to reset for the "new" air pressure but now after I reset the TPMS it comes right back on after driving for a while.

There are only two things I can think of that may cause this issue. Since the sensors are wireless I think maybe my PC may be emitting some RF interference causing the TPMS receiver to think it has lost a signal. A simple form of unintentional RF jamming.

The other option is that one or more of the sensors are bad. If this is the case I will just have to wait until I get home and get an appointment with my Toyota dealer.

Does anyone know what frequency the TPMS emits?

Anyone have a Scan Tool at hybridfest? I think I read somewhere that the Scan Tool can read all four sensors plus the PSI. Dont know where I seen that. I'm trying to search my shop manual PDFs but my laptop is very very very very sloooooooooooow. Been searching for "TPMS" for about 30 min now

Its only a 800mhz PC. I think I might just have to go out to my car PC and do a search on that 2ghz machine.

NoMoShocks · 07-19-2007, 10:44 PM

<div class='quotetop'>QUOTE(TheForce @ Jul 19 2007, 07:19 PM) [snapback]481969[/snapback]</div>

Quote:

I'm having an issue with my TPMS light on the dash. It keeps coming on after I reset it and I have good air pressure. I drove all the way to hybridfest with this issue. This happened before about a week ago after I installed my PC. This was also just after I topped off the tires to 44,42. I thought maybe I just needed to reset for the "new" air pressure but now after I reset the TPMS it comes right back on after driving for a while.

There are only two things I can think of that may cause this issue. Since the sensors are wireless I think maybe my PC may be emitting some RF interference causing the TPMS receiver to think it has lost a signal. A simple form of unintentional RF jamming.

The other option is that one or more of the sensors are bad. If this is the case I will just have to wait until I get home and get an appointment with my Toyota dealer.

Does anyone know what frequency the TPMS emits?

Anyone have a Scan Tool at hybridfest? I think I read somewhere that the Scan Tool can read all four sensors plus the PSI. Dont know where I seen that. I'm trying to search my shop manual PDFs but my laptop is very very very very sloooooooooooow. Been searching for "TPMS" for about 30 min now

Its only a 800mhz PC. I think I might just have to go out to my car PC and do a search on that 2ghz machine.
[/b]

Is there any posibility that you left any connectors unplugged when you had the whole dash apart? It is scary to try and give advice to "The Force". You are legendary you know.

I think you could rule out the electromagnectic interfeirence question by removing power from the Auto PC for a few days and see if the problem goes away. That may be the fastest way.

galaxee · 07-20-2007, 12:31 AM

i seriously doubt we'd be able to keep a scantool for 10 days for hybridfest and the remaining time we'd be up visiting family or i'd see if we could bring one.

what if you turn off the pc? does that fix it?

TheForce · 07-20-2007, 10:19 AM

I havnt tried leaving the PC off for a extended period of time yet because thats where my tunes are. I don't like the radio and I don't have any CDs anymore. Since I don't want my PC on for the MPG challenge I think I will just do another reset and see what happens on the 30 mile trip.

I'm sure I hooked everything back up in the dash when I had it apart. Looks like the TPMS ECU is in the dash. If I have time I may just take my dash apart after the MPG challenge if I still have the issue to see if I did miss a connection.

FL_Prius_Driver · 07-20-2007, 07:39 PM

Are batteries in the sensors and one of these may have gone bad?

007Prius · 07-20-2007, 10:12 PM

Have you checked your spare tire lately?

TheForce · 07-20-2007, 10:16 PM

That would be hard to determine with out the Scan Tool.

The spare does not have a TPM does it? I'm pretty sure it don't.

I tried resetting the light again and failed to do so. I'm starting to think I may have the connector disconnected or it may have come loose.

I will first hunt down where the connector is and see if its all hooked up correctly. I'm hoping that there is a connector back there where I can easily get to it. If I have time I might try to do that while I'm here at hybridfest. If I don't have time I'll just wait until I get home and while I'm at it I will try to give the EV light another try by creating a simulated circuit.

007Prius · 07-20-2007, 10:45 PM

<div class='quotetop'>QUOTE(TheForce @ Jul 20 2007, 09:16 PM) [snapback]482601[/snapback]</div>

Quote:

The spare does not have a TPM does it? I'm pretty sure it don't.
[/b]

My Tundra has one I would think the Prius does too. It's a good idea since most people never check the spare tire so having a sensor in the spare reminds you to check all 5 tires so if you get a flat tire you know you got a good spare to replace the flat.

apriusfan · 07-21-2007, 06:25 PM

<div class='quotetop'>QUOTE(mike m @ Jul 20 2007, 07:45 PM) [snapback]482615[/snapback]</div>

Quote:

My Tundra has one I would think the Prius does too. It's a good idea since most people never check the spare tire so having a sensor in the spare reminds you to check all 5 tires so if you get a flat tire you know you got a good spare to replace the flat.[/b]

The spare tire (at least in the 2007 Prius that I have) has a 60 psi rating which is way higher than the pressure for the rest of the tires. If there was a TPMS sensor in the spare, the TPMS would constantly light up the warning light. The TPMS looks for a variance from the values transmitted by the individual sensors mounted in each tire. Even at 40 psi for the main tires, 60 psi in the spare tire would trigger a warning light, so I tend to doubt that there is a TPMS sensor mounted in the spare tire.

Following are my guesses for the resolution of the problem:

1. Sensors in each wheel are not registered with the TPMS computer.

2. Failure of the battery that powers each sensor. I know it is supposed to be a 10 year battery, but things have been known to fail pre-maturely.

3. Interference by an external source (computer?).

TheForce · 08-01-2007, 05:28 PM

Well after another reset it takes a good ~30 miles before the light comes back on. I made an appointment with my local dealer. I have unplugged my PC today so there wont be a chance for interference when they test it tomorrow.

This is going to run me somewhere between $30 and $100 depending how long they take. I'm going to tell them all I really need is to confirm the scan tool can read the four sensors and their pressure. If it can do that then I know my PC is causing the interference. If thats the case I will just see if they can disable the TPMS. I don't really need it because I check my pressure often enough that the TPMS is basically useless to me.

07-19-2007, 10:19 PM	#1
TheForce I Plug-In My Prius Join Date: May 2005 Location: Wheelersburg, Ohio Posts: 2,131 My Car: 2006 Prius Package: #7 Nominated 7 Times in 2 Posts TOTM Awards: 0 Friends: 18	I'm having an issue with my TPMS light on the dash. It keeps coming on after I reset it and I have good air pressure. I drove all the way to hybridfest with this issue. This happened before about a week ago after I installed my PC. This was also just after I topped off the tires to 44,42. I thought maybe I just needed to reset for the "new" air pressure but now after I reset the TPMS it comes right back on after driving for a while. There are only two things I can think of that may cause this issue. Since the sensors are wireless I think maybe my PC may be emitting some RF interference causing the TPMS receiver to think it has lost a signal. A simple form of unintentional RF jamming. The other option is that one or more of the sensors are bad. If this is the case I will just have to wait until I get home and get an appointment with my Toyota dealer. Does anyone know what frequency the TPMS emits? Anyone have a Scan Tool at hybridfest? I think I read somewhere that the Scan Tool can read all four sensors plus the PSI. Dont know where I seen that. I'm trying to search my shop manual PDFs but my laptop is very very very very sloooooooooooow. Been searching for "TPMS" for about 30 min now Its only a 800mhz PC. I think I might just have to go out to my car PC and do a search on that 2ghz machine. __________________ 2006 Prius Barcelona Red Package #7. Picked up 2006/01/02 *Hybridfest 2007 & 2008 Peoples Choice Award * For a list of my mods visit http://www.jaygroh.com

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07-20-2007, 12:31 AM	#3
galaxee running WOT until out of fuel Join Date: Mar 2005 Location: central NC/ western WI Posts: 9,072 My Car: 2005 Prius Package: #5 Nominated 5 Times in 3 Posts TOTM Awards: 0 Friends: 21	i seriously doubt we'd be able to keep a scantool for 10 days for hybridfest and the remaining time we'd be up visiting family or i'd see if we could bring one. what if you turn off the pc? does that fix it?

07-20-2007, 10:19 AM	#4
TheForce I Plug-In My Prius Join Date: May 2005 Location: Wheelersburg, Ohio Posts: 2,131 My Car: 2006 Prius Package: #7 Nominated 7 Times in 2 Posts TOTM Awards: 0 Friends: 18	I havnt tried leaving the PC off for a extended period of time yet because thats where my tunes are. I don't like the radio and I don't have any CDs anymore. Since I don't want my PC on for the MPG challenge I think I will just do another reset and see what happens on the 30 mile trip. I'm sure I hooked everything back up in the dash when I had it apart. Looks like the TPMS ECU is in the dash. If I have time I may just take my dash apart after the MPG challenge if I still have the issue to see if I did miss a connection.

07-20-2007, 07:39 PM	#5
FL_Prius_Driver Senior Member Join Date: Jun 2007 Location: Tampa Bay Posts: 1,227 My Car: 2001 Prius Package: N/A Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 0	Are batteries in the sensors and one of these may have gone bad?

07-20-2007, 10:12 PM	#6
007Prius Join Date: May 2007 Posts: 32 My Car: Package: Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 0	Have you checked your spare tire lately?

07-20-2007, 10:16 PM	#7
TheForce I Plug-In My Prius Join Date: May 2005 Location: Wheelersburg, Ohio Posts: 2,131 My Car: 2006 Prius Package: #7 Nominated 7 Times in 2 Posts TOTM Awards: 0 Friends: 18	That would be hard to determine with out the Scan Tool. The spare does not have a TPM does it? I'm pretty sure it don't. I tried resetting the light again and failed to do so. I'm starting to think I may have the connector disconnected or it may have come loose. I will first hunt down where the connector is and see if its all hooked up correctly. I'm hoping that there is a connector back there where I can easily get to it. If I have time I might try to do that while I'm here at hybridfest. If I don't have time I'll just wait until I get home and while I'm at it I will try to give the EV light another try by creating a simulated circuit.

08-01-2007, 05:28 PM	#10
TheForce I Plug-In My Prius Join Date: May 2005 Location: Wheelersburg, Ohio Posts: 2,131 My Car: 2006 Prius Package: #7 Nominated 7 Times in 2 Posts TOTM Awards: 0 Friends: 18	Well after another reset it takes a good ~30 miles before the light comes back on. I made an appointment with my local dealer. I have unplugged my PC today so there wont be a chance for interference when they test it tomorrow. This is going to run me somewhere between $30 and $100 depending how long they take. I'm going to tell them all I really need is to confirm the scan tool can read the four sensors and their pressure. If it can do that then I know my PC is causing the interference. If thats the case I will just see if they can disable the TPMS. I don't really need it because I check my pressure often enough that the TPMS is basically useless to me.