Bad external temp readings

Have a '02 Envoy.
Anyone seen low readings on their digital Ext Temp gauge?

It's about 85 degrees out and my gauge starting going south on my commute to the office -- from upper 70s to -24 by the time I parked.

After parked for a couple of hours, the gauge reads correctly initially but quickly goes down inaccurately (75 degrees to 38 within minutes).
By the time I returned from a lunch run, it was below zero once again..

I know the air temp sensor is along the plastic air intake 'tube'. Could it be this part failing? Where is the external temp sensor/thermometer located?

Thanks for any ideas... Just got the vehicle two months ago and it's been trouble free (until now).

The ambient air temp sensor is behind the middle of the grille. It is clipped to the radiator/ hood latch support.

They are known to be a problem, and I have replaced MANY.
It is an easy replacement, that takes about 5 minutes.

-Take off the top clips on the grille (4 across the top)
-Lean grille forward just far enough to access the sensor.
-Unclip with a clip tool or similar.
-Unplug old one and reinstall new one in reverse order of installation.
-No calibration or programming needed.

The little plastic one on the intake is the IAT (Intake Air Temperature) Sensor, and has nothing to do with the mirror thermometer.

Hope this helps.

Hey -- Thanks a ton for the response!

I stopped by my GMC dealer and got the part for $14.90+tax this morning after running the situation by the parts counter. Your message gives me the added confidence that replacing the part will solve the issue. The timing of the failure coincides with the arrival of humidity in the Ohio valley so, again, I appreciate the response.


The ambient air temp sensor is behind the middle of the grille. It is clipped to the radiator/ hood latch support.

They are known to be a problem, and I have replaced MANY.
It is an easy replacement, that takes about 5 minutes.

-Take off the top clips on the grille (4 across the top)
-Lean grille forward just far enough to access the sensor.
-Unclip with a clip tool or similar.
-Unplug old one and reinstall new one in reverse order of installation.
-No calibration or programming needed.

The little plastic one on the intake is the IAT (Intake Air Temperature) Sensor, and has nothing to do with the mirror thermometer.

Hope this helps.

You would think they would find a better place than the grille to put the sensor. All the engine heat and stuff liekt hat.

Does anyone have a GM part number for the temp sensor? My wifes mirror just says "OC". I'm hoping to find it cheap at gmpartsdirect.com.

Thanks,
Alan

1504-7946 is the part number