TPMS and fuel cap oddities July 06, 2022, 08:57:47 pm I’ve been camping in the Uinta Mountains of Northern Utah the last week or so and other than having no cell service it’s been absolutely wonderful. The camps are located at 10,000+ feet and I believe that is the reason for one of my oddities.#1. On two different occasions the Ford onboard computer warned me to check the fuel cap. The actual message was “Check Fuel Inlet”. Both times I pushed the OK button and then pulled over to loosen and re-tighten the fuel cap. That seamed to fix the problem. I’m assuming the high altitude was the reason for the warning message.#2. The other oddity was with the aftermarket TPMS and is just really strange. I can’t imagine how it could be related to the high elevation but who knows. I was driving south on Hwy 150 and the over temperature alarm sounds off for my toad’s right rear tire. Now get this… it says the temperature is 331 degrees F. Now I know I’m not pulling a flaming torch behind me but it’s still a bit unnerving to see such a high temperature displayed. Anyway, I pull over and turn off the LD and walk back to the toad. Of course everything is fine and nothing is excessively hot or smoking. I return to the LD and restart the engine which restarts the TPMS display and now the toad’s right rear tire reads 89 degrees F with no further malfunction.Both things happened within about a mile of each other… the first fuel cap warning and the TPMS over temperature alarm. The two systems are not connected in any way and I just find it strange that they happen so close together. Coincidence???- John
Re: TPMS and fuel cap oddities Reply #1 – July 07, 2022, 04:54:51 am Hi John. Yes coincidence. The fuel tank is pressurized to only vent vapors through an activated charcoal canister. If the tank pressure is too low the engine computer figures that either the fuel cap is too loose, or missing altogether. The programmer didn't realize that high altitude could give an erroneous reading. (hey it works on the lab bench!) The tire TPMS receiver may have gotten a garbled transmission, from one of the sensors, or just about anything else while it thought it was reading that particular tire position. Any planes with radar altimeters fly over about that time? Police with radar guns? Some roadside sensor happen to transmit just as you passed it? Things like that. RonB 1 Likes
Re: TPMS and fuel cap oddities Reply #2 – July 07, 2022, 10:01:22 am Hi Ron,I know coincides happen but it’s kind of like getting hit by lightning twice on the same day by different storms. The TPMS alarm went off on a stretch of highway with no one and no buildings around, just me and the trees. I’m going to right it off as a glitch in the system. Thanks for the explanation of how fuel vapors vent.- John
Re: TPMS and fuel cap oddities Reply #3 – July 07, 2022, 10:25:19 am A note on the external TPMS systems. I used to think the temp readout was worthless, as it does not represent internal tire temps accurately. However, I will often get an unrealistic tire pressure reading, and usually the tire temp is what a cold tire would read. Then I know that the sensor reading is bad, not the tire.Steve
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