I am not sure what’s going on. I had the ice possible light on. I replaced both of the ambient air temperature sensors with factory GM parts. My review mirror is reading correctly but I am still getting the ice possible light. I tried swapping out sensors and I’m still getting it. I couldn’t find any kind of shirt that was visible in the wiring. What else could be the culprit? 2003 h2.

 

The temperature sensor with Light Green/Black and Brown wires is the one of interest, it connects to the HVAC which communicates its value via the BCM to the cluster display:-



Possibilities are:-

1. Wiring fault
2. Faulty Sensor (swapped?)
3. Faulty HVAC Module.

Double Check the Sensors
The sensors are negative temperature co-efficient thermistors i.e. resistors that decrease with temperature, they are not polarized or active in any way and usually very reliable.
Unplug both sensors, measure and compare their resistances they should be similar values, if so it's not the sensor (Note if you unplug a sensor with the HVAC ON it can take quite some time for the reading to stabilize)
According to GM at 68°F/20°C the resistance should be around 1.25KΩ, at 32°F/0°C = 3.20KΩ (note this info is unverified but will give you an idea)

HVAC
It's easy to pull-out the HVAC unit by slackening the top center console screws and pulling the plastic forward. Unplug the Grey connector C2 and measure the resistance between pins B (Green) & K (Brown) again this value should be similar to the above, if not check the wiring, if it is the issue is most likely the HVAC Module.

For the HVAC cost-wise it would be worth looking for dry joints on the PCB.
The HVAC temperatures can also be read using a diagnostic scan tool such as a Tech2.

For HVAC access and internals etc
Hope this helps, keep us posted 👍✔️
[Awaiting Resolution]

 

Awesome info. Thank you so much for posting it. I did swap the sensors out it didn’t make a difference. I checked the ohmage on both of them and they were both close to 9.32K ohms.

I will definitely start checking all the wiring. I just replaced the HVAC control panel 5 months ago and I think it was a dorman unit from O’Reilly auto parts. So maybe there is something wrong with it. I think they give a lifetime warranty, so that’s good. I’ll get on testing everything tomorrow and report back with my findings.
I appreciate all the good info

 

Fonzie any luck?