Ambient Temp Sensor - normal behavior?
 

What is the typical behavior of the ambient temperature sensor on a 2017 MDX after you turn the car on? Recently when the ambient air temp has been near 40f and the MDX is turned on, the temp readout can start at ~50f, go up to 60f, and then settle down to just above 40f.

In our 2003 530i, the readout is always very close to the true ambient as soon as the car turns on and doesn't oscillate.

Is our sensor bad, is something else faulty, or is this behavior typical?

Mine resides in a garage so its always off for the first couple of minutes. When parked after driving the heat from the motor can effect the sensor. I never believe it until after anout 5 minutes of driving. I have notices this one is a lot faster responding than the one that was in my Suzuki.

I've noticed behavior like that. It is the least accurate and most wildly-fluctuating ambient temp sensor I've ever had.

This appears to be normal behavior of the Acura temp sensors. There have been multiple reports about this in the past from the 2014 model on up, and I guess this is how it calibrates.

If you search the net you'll find articles about how Honda products have certain 'logic' in the way their temp sensors work. The crux of the issue is that, once the engine reaches at-or-near operating temperatures, the sampling of the ambient air is done in longer intervals. The "logic" is that if the area around the radiator is hot, it may provide inaccurate readings since the sensor is near that part of the vehicle. So you may find that pulling out of a garage into the cold, the temp will move at a certain pace towards the proper ambient reading, and then slow way down as the car warms up. I agree that other vehicles (such as the Mini cooper my kids had) are much more stable in reading than Honda products, especially in the first few minutes of driving. After a while both behave similarly after the Honda has adjusted the reading to ambient....

andy

Please note that the "outside temp sensor" (OTS) measures the temperature near the road surface, and not the actual ambient temperature as in weather forecast reports.

According to Honda, this road temperature information is used to warn the driver, of the possibility of black ice on the road surface when the road temp is near freezing.

It right around 32f outside yesterday morning when I pulled out the garage to take my daughter to school and the temp near the garage floor was around 46f. When I turned the MDX on, the temp sensor read 60f and within a few minutes of driving, the sensor was in the mid 40's and eventually reached 32f. Since nothing around the car was near 60f, I'm trying to understand if I have a faulty sensor regardless of the typical delay how Honda ambient temp sensors function.

As a driver in inclement I'd want to know immediately if the surface air temp was above or below 32f and not have to wait 3 minutes to figure it out vs relying upon the perceived traction I was getting/not getting. I simply don't understand Honda's logic Andy wrote below.

I'll take more observations and return back once I think I better understand the pattern.

The following is extracted from the 3G MDX user's manual :

"The temperature sensor is located in the front bumper.
Road heat and exhaust from another vehicle can affect the temperature reading when your vehicle speed is less than 19 mph (30 km/h).
It may take several minutes for the display to be updated after the temperature reading has stabilized."

So if it takes a few minutes of traveling fast to obtain a correct road surface temp, your MDX's OTS is working correctly by design.

So this is what I observe just about every day... When I come back from taking my son to school, the temperature reading always shows a temp in the 20s, which is accurate. I park in the garage. During the day the garage warms up and I leave around 3pm, with the ambient temperature in the garage around 60. But upon starting the car, the temperature reading starts in the 20s and climbs quickly to the actual temperature.

I would have expected the initial display to be the garage temperature or slightly higher depending on the temperature of the engine. I'm bringing this up only because this doesn't seem to match what others in this thread are reporting...

IMO, they over engineered this
display what the temp sensor sees
in the RL and RLX, the temp would only adjust according to a formula based on time and speed. Not sure about MDX

This happens to my 15 MDX as well, it will affected by the hot engine when the car is parked, but during driving, it will reach to the accurately reading as shows in my phone.