Diagnosing an intermittent P0404 (EGR Valve Sanity) on my 2008 Unlimited. What I noticed this morning while watching temps with my Torque app on my phone, that the ambient temp sensor was showing 50 for at least 5 miles, then it finally jumped to 53.6. Temp outside was about 53, and if my memory is correct it would climb and lower based on if I was driving, speed and engine temp. So at a light I remember it creeping up when I was stopped. I will check my logs I snagged at home when I get off work.

What is bothering me the most is how it seems to only measure in whole numbers, no decimals like every other gauge. As I had it in Fahrenheit it was jumping in increments of 1.8.

Is this all normal, or should I be concerned about this sensor or the readings I am getting?

 

Mine reads only in whole numbers.
The only way to check accuracy is to compare it to a calibrated thermometer.

Here is how the JK's ambient temp sensor behaves. Below it, is what I did to check accuracy.
_________________________________
Vehicle with the key off for more than 4 hours...The CCN will update the ambient temperature reading immediately.

Vehicle with key off for more than 2 hours but less than 4 hours....The CCN will update the ambient temperature reading immediately after vehicle reaches above 20 mph (with no duration constraint) and will update every 500 ms thereafter.

Vehicle with the key off for less than 2 hours...The CCN will display the last temperature reading (which is stored in memory) just prior to the ignition being turned off. The CCN will not update the value in the display until the car has been driven at 20 MPH or above for 3 consecutive minutes.

If the vehicles speed and drive time doesn't meet the criteria the CCN will
continue to display the stored value until the criteria is met.

Once the criteria is met, then the CCN will update the display every 500 ms based off of the ambient temperature sensor output.
_________________________________






For your reading pleasure:

I did some tests when I went to the store today.

I have two thermometers.
One is calibrated and certified. (Alcohol Thermometer)
The other has a year long history of reading the same as the calibrated one, when sitting next to it. (Mercury Thermometer)

I taped the mercury thermometer next to the JK sensor.
The alcohol thermometer was in the passenger's front seat.
All the windows were open. It was a heavily overcast day.

After about 10 minutes of driving, I noted the following results.

The JK display read 70°F
The thermometer next to the sensor read 72°F
The thermometer in the cab read 71.5

After the return trip, I noted the following results.

The JK display read 69°F
The thermometer next to the sensor read 71°F
The thermometer in the cab read 71°F

After I parked and shut off the engine, I put the thermometer that was in the cab, next to the one by the JK sensor.
After 5 minutes, both test thermometers read 78°F. (Engine heat radiating from grill.)

 

I've never quite understood why they did that. I get that they're trying to avoid displaying an inaccurate reading, hence the speed and mileage requirement to ensure good airflow around the sensor - but the result of this algorithm is that they display an inaccurate reading anyway (one that's two hours old).

Not really a big deal most of the time, but it's annoying when the temperature drops quickly below freezing and you hop in your Jeep and drive over that shiny spot in the road thinking it can't be ice because your thermometer still shows the temperature of 35F from 2 hours ago...

 

It seems to me the reading would be more accurate than if it were allowed to display what it sensed after being bathed in engine bay heat.

Ice can be on the road when the air is above 32°F, and water can be on the road when the air is below 32°F.
The ambient air temp display on any vehicle can't be depended upon to indicate whether or not there is ice on the road.