2012 Honda CR-V: TPMS Light Follow-Up
November 24, 2012
A couple weeks back the TPMS light came on while I was headed to the airport for an overseas business trip, but it winked off once the outside air temperature -- and the tires -- warmed up.
That was the working theory at the time, anyway.
Here's what I found when I got back.
All four tires measured 25 psi or thereabouts at an air temperature of about 75 degrees, and I made the check after rotating the tires, a job that took 15 minutes. But it takes about 30-40 minutes for a tire to cool down after being driven at speed, so the true "cold" pressure in this case is probably a half-pound or so lower than what's shown here. Let's go with 24 psi.
The CR-V's tires are supposed to be set at 30 psi, but the typical TPMS system doesn't raise the alarm until a tire is 25% below the target pressure. In this example that works out to 22.5 psi.
Sharp-eyed readers will note that 24 psi is not sufficiently low to trigger a warning. And indeed, when I drove it into the garage for this check, the TPMS light wasn't on.
But on the morning in question the car had been parked outside overnight in temperatures at least 30 degrees colder. At some point during the night, it seems possible that the tire pressure dropped below the magic 22.5 psi threshold. Then, as the sun came up and the car was driven a bit, the pressures came up and the light shut off.
There's no leak involved here -- all tires ooze a little air over time and in any case we're talking about all four tires here, not just one.
But here's the weird part: the same thing happened when I was in Tonopah, Nevada last month and that time the tire pressures checked out OK at 29.5 to 30 psi. I can only surmise the gauge I used that time (different from this one -- a buddy's) was inaccurate; maybe the tires were low in Nevada after all. It certainly would explain that false alarm.
The alternative is all four tires really did lose 6 to 8 psi in the ensuing 5 weeks. A pound or two I could, believe, but not that much.
No matter. Now they're back at the correct pressure and all is well. And I'm going to advise my buddy to round-file his tire pressure gauge and buy a new one.
Dan Edmunds, Director of Vehicle Testing @ 11,098 miles