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GMWrencher, ASE Certified Technician
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Experience:  100% GM Certified ASE Master Automobile Medium/Heavy Truck. Licensed State Auto Inspector
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2007 impala ltz: ambient air temp sensor and did the reset..programmed

Resolved Question:

2007 impala ltz replaced ambient air temp sensor and did the reset (a/c and recirc simultaniously). The temp updates but after a little while it reads wrong temp again. Does this have to be programmed for the car, or is reset enough. Also, it was replaced because on hot days using remote start the A/C would not come on. Was this the right sensor to replace? I have read some arguements in another thread about a manifold air temp sensor being the culprit and not the ambient air temp sensor. Any help would be appreciated.
Submitted: 6 years ago.
Category: Chevy
Expert:  GMWrencher replied 6 years ago.

Hello, I will do my best to help answer your General Motors Vehicle questions.


Remote start cooling/heating is dependent on outside air temperature, not intake air temperature.

Are you 100% sure you replaced the correct sensor?

Explain why you think its reading wrong.?

Please explain how much it is off and how and where you are driving.

Edited by GMWrencher on 7/3/2010 at 2:23 PM EST
Customer: replied 6 years ago.

Replaced the plug-in sensor mounted on the radiator support, just under the shroud on the driver's side. Bought new ambient air sensor from dealer and it matched what was taken out. Before replacement it read about 50 deg low. After replacing it was about the same. Read about AC/Recirc to reset and it jumped up to where it should be, but the next time the car sat, it was off again. The car is black and today it is around 100 deg. Started the car at lunch and it read 107 deg. Did the AC/Recirc reset and it jumped up to 140, which is where I would expect it to be sitting in direct sunlight. Car is driven in Boston, MA

Expert:  GMWrencher replied 6 years ago.

Maybe today... Its hot all up and down the east coast, but to be honest rarely see ambient temperature sensors spike that high. You may have a condition with connections or possible corrosion within the sensor circuits. It may not be apparent, but salt and brine can wick into sensor circuits, and with that sensor catching the incoming air it may have an issue. If the circuits have high resistance or have an issue with signal bleed from one to another, it will be noticed as an incorrect reading.


Do you notice an issue while driving in the rain or moisture, or more when its dry?

Does weather change the reading?


Read this quote from the operation, and compare to your issue.


Outside Air Temperature Sensor
The air temperature sensor is a 2-wire negative temperature co-efficient thermistor. A signal and low reference circuit enables the sensor to operate. As the air temperature surrounding the sensor increases, the sensor resistance decreases. The sensor signal decreases as the resistance decreases. The sensor signal varies between 0-5 volts. The HVAC control module converts the signal to a range between 0-255 counts.

The ambient sensor operates within a temperature range between -30 to +51°C (-22 to +123.8°F). The driver information center (DIC) displays the ambient air temperature that it receives from the HVAC control module through a GMLAN message. If the HVAC control module has determined that the ambient temperature sensor has failed the DIC will display 86°C (186°F) if shorted to ground and -40°C (-40°F) if open or shorted to voltage.

The HVAC module controls the temperature displayed on the DIC and the instant update feature as follows:


When the HVAC module A/C and RECIRCULATION buttons are pressed simultaneously.
Updates temperature display instantly.

At start up with the engine OFF more than 3 hours
Displays actual outside temperature

At start up with the engine OFF less than 3 hours
Displays last stored temperature unless temperature has decreased. The temperature reading is always instantly up dated if ambient air temperature has decreased.

Vehicle moving above 16 km/h (10 mph) for 5 minutes
Updates temperature display at a slow filtered rate.

Vehicle moving at 51 km/h (32 mph) or greater for 2.5 minutes
Updates temperature display rapidly.

When the ambient air decreases.
Updates temperature display rapidly.

Edited by GMWrencher on 7/6/2010 at 6:32 PM EST
GMWrencher, ASE Certified Technician
Category: Chevy
Satisfied Customers: 439
Experience: 100% GM Certified ASE Master Automobile Medium/Heavy Truck. Licensed State Auto Inspector
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