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The "Sorta Stock" Subaru has OEM TPMS sensors (made by Schrader) that supposedly report individual tire pressure and temperature every few seconds.  Sadly, Subaru only uses a generic idiot light to report any TPMS tire pressure problems.  Does anyone know of a way to read the detailed data being reported by the sensors and to display it?  Supposedly, the OEM Subaru sensors use a standard frequency and data format, so it seems it should be possible.  Any thoughts?

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Last edited by Sorta Stock
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So, it looks like I have two options at this point, assuming I want to retain compatibility with the OEM in-car system.

Option one: Build a solution.  I have a cheapie (<$10) 315 MHz receiver on order that should be able to receive OEM sensor data.  Will enjoy trying to decode the data stream.

Option two: Buy new sensors that output both OEM Subaru data and Ford compatible data streams and then buy a unit that can display the  detailed Ford data. This would be at least $200  or more for parts and require replacing the sensors on all tires for additional $$.

Option 2 should work if I can't figure anything else out, but I'd really like to have a go at decoding the OEM wireless data stream. 

Yes, I'm a nerd. 

Last edited by Sorta Stock

The RF circuit boards that should be able to read/write TPMS data have arrived.  Photo shows the two devices on a graphic novel for size comparison.  The smaller is for transmit and the larger for receive.  They are really tiny.  I also bought new Subaru compatible TPMS sensors since the OEM ones are over 12 years old.  These new sensors supposedly simultaneously output multiple manufacturer formats, which should be a plus for decoding.  Also, if they output both Subaru and other formats (such as Ford), I should be able to buy an off the shelf display unit that will display detail data for each individual tire.   Still want to try decoding directly using an Arduino if I can. 

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So far, I've replaced the sensors and the new sensors are functioning properly with the OEM TPMS in the Subaru.  The new sensors can also be read individually using a TPMS reset tool.  

The bad news is that I've really made no progress with the hand built receiver.  I've done some rudimentary work trying to read data from the sensors, but the results have been disappointing so far.  The sensors will activate just fine with the TPMS tool, but I am seeing nothing as far as a data stream.  The lack of reading any data so far could be the result of my lack of understanding or the fact that I bought el-cheapo radio components.  US TPMS sensors typically transmit data on 315 Mhz, so it should be possible to use the receiver portion to at least see the data..  The transmitter portion is not of use since 217Mhz (I believe) is the frequency that is transmitted by the TPMS tool to activate the sensor to read data.  Here is the transmitter receiver pair I bought:  https://www.amazon.com/gp/prod...psc=1&pldnSite=1

 

No real progress to report other than capturing RF data from the sensors using an RTL-SDR.  Sadly, I have made zero progress in decoding the data.  My understanding is that it uses FSK with Manchester encoding, but I can't even get the data toe code to the point where I can see the individual TPMS serial numbers.  At this point, I'm considering just mothballing the TPMS project and concentrating on making sure the WRX is ready for September. 

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