On the 2002 GMC Envoy, when the outside temp display is not working, this is most commonly due to a problem with the Ambient Air Temp sensor. The air temperature sensors are a 2 wire negative temperature co-efficient thermistor. As the air temperature surrounding the sensor increases, the sensor resistance decreases. The sensor signal voltage decreases as the resistance decreases. The sensor operates within a temperature range between -40°C (-40°F) to 101°C (215°F) . You can find the sensor under the hood mounted to the radiator fan shroud. Carefully inspect the electrical connector and wire harness for any loose, broken or damaged wires. If the visual inspection checks ok, then replacement of the Ambient Air Temp Sensor should solve the problem.
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