2014 Jeep Cherokee: Mysterious Tire Pressure Monitoring System Error Warning
October 29, 2014
I had a lot going on this past weekend, and found myself crisscrossing L.A. and Orange counties in our 2014 Jeep Cherokee Limited. Saturday morning's chosen road was particularly pleasant and I was really enjoying myself until...
...the Tire Pressure Monitoring System (TPMS) warning light started blinking.
The pressure display screen automatically popped up on the driver display screen, but it showed all four tire pressures to be bang-on the specified pressure of 33 psi. I pulled over and confirmed this with a quick check, but as I was doing it I knew it wasn't necessary.
A blinking light, you see, means a problem with the system itself, not the tire pressure. A steady light means you have a low tire. This distinction is coded in the TPMS regulations and noted in the owner's manual.
So I made a mental note and went about my business.
The blinking warning persisted for about a minute or two. After that it went solid as if to say, "You've seen my alert. Now I'm going to back it down a notch so you don't get annoyed with me and trot out the electrical tape."
My errand-filled day resulted in many stops, and this pattern repeated at every restart in order to make sure the driver (me) didn't forget to have it checked out. The warning light would blink, the tire pressure display screen would override whatever was on the display screen, and after a minute or so the blinking light would downgrade to always-on status.
At one point I was paging through the driver information screen and found a "Service TPMS system" alert on the Stored Messages screen. Why wasn't this screen the one that automatically popped up? If it's a fault with the system itself then there's little point in conjuring up the tire pressure display. Why leave the discovery of this clarifying service message to chance?
But I digress.
For no apparent reason it all went back to normal several key-starts and some dozens of miles later. No more blinky light at restart, the tire pressure screen retreated to its usual background position and the Stored Messages screen cleared itself. It's as if I dreamt the whole thing.
So what happened?
I'm not exactly sure, but I have a couple of guesses. The central brain could have missed a few reports from one of the wheel-mounted tire sensors. A low sensor battery might do it, but they're supposed to be good for 10 years. Maybe I drove through a region of high electromagnetic interference. I don't recall any mysterious radio towers along my route, though. And the nearest military installation is dozens of miles away.
Besides, the pressure screen that popped up always displayed numbers that made sense. And as I drove they changed up and down one or two psi in response to heat, sun load and driving enthusiasm, as per usual.
Whatever it was, the fact that it took time to reset itself makes sense. The system would have to see a string of uninterrupted successful transmissions to rebuild "confidence" in the data and extinguish the light. The same thing happens with some systems when you install a new wheel sensor with an unfamiliar serial number. Such systems can "learn" that an unfamiliar sensor "belongs" after enough successful and persistent transmissions are received.
Still, we're going to keep an eye on it and have it checked out at the next service visit. Before that I may drive back to the same spot to see if some sort of weird local interference is to blame.
Dan Edmunds, Director of Vehicle Testing @ 6,616 miles