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Do tire pressure sensors operate on a specific RF frequency?

I just got my car back from the place that fixes it, and noticed that the one tire keeps reporting that it is low; how low? 0 psi. Now, every time I start my car, the tire pressure light comes on and I get a nice message about "low tire pressure"; but it just isn't true...my tire is fully inflated. Now the embedded systems programmers who programmed my car and the tire sensors to talk with one another could easily have coded something like, if front left tire sensor not found, display "err" or -1, but I'm sure this wasn't in the budget of my crappy 2010 Chevy Malabu...

But anyway...they have to communicate somehow, so what frequency do they use?

  • As an embedded systems programer… They programmed it to return 0 :-) What you really want is for them to return a meaningful error, a most reasonable request. Perhaps they were contained on memory, or maybe the boss said "good enough". – dlu Jul 27 '16 at 23:55
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I suspect your specific issue is that the GM "Body Control Module" has lost (or never had) the unique RFID for the offending sensor. Since they all work on 315MHz, each sensor must scream out its unique coded Radio Frequency ID so the BCM knows which tire is low, and not get confused when passing another Malibu (or Tahoe, or other GM vehicle that shares the same system) and report your neighbor's tire pressures rather than your own.

In your case, I'll bet the sensor is communicating just fine, but the BCM refuses to listen. Perhaps the difference is in the word "communication" -- while I have one definition, my girlfriend may have quite another...

Unfortunately, I think yours requires some specialized tooling to trigger the "learn" process which binds the sensor RFIDs to your personal BCM. Some vehices use a powerful donut shaped magnet placed around the valve stems to trigger this process (I own that tool), but if I recall that's for Chrysler and not for GM. My expensive SnapOn scan tool can't even do it, along with other GM woes like radio replacement, keyless entry, HVAC controls, or instrument cluster repairs. The imperial BCM is quite the dictator, and the complexity makes it very difficult/expensive to perform certain repairs by independent shops.

Now, if this worked before you took your vehicle in to get "fixed", I feel the repair shop owes you a BCM TPMS synchronization. On the other hand, I've seen major tire shops that disclaim this in their receipt fine print, because again some of that tooling (handheld computer thingy) is eye-watering expensive. And the sensors themselves can easily get broken if you aren't careful breakihg the tire off the rim.

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Some of them have to communicate :-)

There are two types of tire pressure monitoring systems (TPMS) in common use:

  • Indirect TPMS – these systems infer tire pressure from the ABS wheel speed sensors, so they don't use RF to communicate. Indirect systems don't know the actual tire pressure, instead they know about the relative pressures that they infer from the ABS data.

  • Direct TMPS – these systems use a sensor on/in the wheel to measure the actual pressure (and sometimes temperature). These need to communicate. A quick Google search found a site selling replacement sensors for your car and it looks like they run at 315MHz.

There is a pretty good article on tire pressure monitoring systems on Wikipedia, Bridgestone also has an article on it.

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