Outside air temperature problem
07-27-2008, 08:07 PM
#11
Join Date: 07-27-2008
Location: Hillsboro, Oregon
Posts: 9
This is a description of how the OAT sensor works. Its more complicated than one would think.
You will notice the very interesting information on how they changed the location of the sensor for 2008 models.
Outside Air Temperature
The outside air temperature is read by the body control module (BCM) and transmitted over serial data to the instrument panel cluster (IPC) for display in the driver information center (DIC). The BCM provides the logic for reading the outside air temperature sensor. The BCM sends the temperature to the IPC in Celsius. The IPC is responsible for displaying the temperature and converting to Fahrenheit.
The sensor operates within a temperature range of -40°C to +60°C (-40°F to +140°F). The ambient air temperature sensor is mounted in the forward engine area, behind the left front headlamp. This causes an air flow issue due to the sensor's location and can effect the ambient air update display parameter in the DIC of the vehicle. For model year 2008 the ambient air temperature sensor will have a new location closer to the grill airflow. In the present position, it is exposed to limited airflow from the grill before it reaches the radiator. The sensor signal varies between 0-5 volts.
The ambient air temperature sensor algorithm uses 3 pieces of information, outside air temperature data, vehicle speed, and time the engine was turned off.
The ambient air temperature is updated and displayed by the DIC under the following conditions:
Conditions
DIC Display
If the current ambient air temperature value is cooler than or equal to the old temperature value. Vehicle speed is in excess of 33 mph.
Displays outside actual temperature. Display updates every second.
If the current ambient air temperature value is warmer than the old temperature value. Vehicle speed is less than or drops below 18 mph.
Displays last temperature recorded during last ignition cycle. No update.
New ambient temperature exceeds the previous ignition cycle recorded ambient temperature, and vehicle speed exceeds 18 mph but is less than 33 mph.
Displays outside actual temperature. Display will be updated at a slow rate.
Vehicle speed is greater than or equal to 45 mph. (for at least 3 minutes)
Displays outside actual temperature Display updates at a quicker rate.
You will notice the very interesting information on how they changed the location of the sensor for 2008 models.
Outside Air Temperature
The outside air temperature is read by the body control module (BCM) and transmitted over serial data to the instrument panel cluster (IPC) for display in the driver information center (DIC). The BCM provides the logic for reading the outside air temperature sensor. The BCM sends the temperature to the IPC in Celsius. The IPC is responsible for displaying the temperature and converting to Fahrenheit.
The sensor operates within a temperature range of -40°C to +60°C (-40°F to +140°F). The ambient air temperature sensor is mounted in the forward engine area, behind the left front headlamp. This causes an air flow issue due to the sensor's location and can effect the ambient air update display parameter in the DIC of the vehicle. For model year 2008 the ambient air temperature sensor will have a new location closer to the grill airflow. In the present position, it is exposed to limited airflow from the grill before it reaches the radiator. The sensor signal varies between 0-5 volts.
The ambient air temperature sensor algorithm uses 3 pieces of information, outside air temperature data, vehicle speed, and time the engine was turned off.
The ambient air temperature is updated and displayed by the DIC under the following conditions:
Conditions
DIC Display
If the current ambient air temperature value is cooler than or equal to the old temperature value. Vehicle speed is in excess of 33 mph.
Displays outside actual temperature. Display updates every second.
If the current ambient air temperature value is warmer than the old temperature value. Vehicle speed is less than or drops below 18 mph.
Displays last temperature recorded during last ignition cycle. No update.
New ambient temperature exceeds the previous ignition cycle recorded ambient temperature, and vehicle speed exceeds 18 mph but is less than 33 mph.
Displays outside actual temperature. Display will be updated at a slow rate.
Vehicle speed is greater than or equal to 45 mph. (for at least 3 minutes)
Displays outside actual temperature Display updates at a quicker rate.
07-28-2008, 01:14 AM
#12
Member
Join Date: 07-24-2008
Location: St Louis Missouri (Affton)
Posts: 34
Outside Temp Problem
This may seem like nothing to some folks, but I paid for this vehicle and I want the options to work properly. Has anyone had the dealer fix the problem or found out from GM what the problem is ?
Mine is the same as the rest, sticks on one temp jumps to another temp at times then sticks there. HELP !
2008 HHR SS Born 06/12/2008
Mine is the same as the rest, sticks on one temp jumps to another temp at times then sticks there. HELP !
2008 HHR SS Born 06/12/2008
07-28-2008, 07:07 PM
#13
Senior Member
Join Date: 06-21-2008
Location: Dallas, Texas
Posts: 332
I was concerned about mine being broke when I first got it. After a few weeks, it's perfectly fine. I don't know if I just got used to how it works or what. But it was 105 driving home, which was friggin hot, but correct, lol.
I say give it a couple of weeks before you bring it in. Unless it's off by 30 degrees or something.
I say give it a couple of weeks before you bring it in. Unless it's off by 30 degrees or something.
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