Pinpoint Test AH: The Outside Air Temperature Display Is Inoperative/Incorrect
Instrumentation, Message Center and Warning Chimes
Pinpoint Test AH: The Outside Air Temperature Display Is Inoperative/Incorrect
Refer to Wiring Diagram Set 60, Instrument Cluster for schematic and connector information Electrical Diagrams.
Normal Operation
The ambient air temperature sensor is hardwired to the PCM through separate input and return circuits. The PCM provides a reference voltage to the ambient air temperature sensor and monitors the change in voltage resulting from changes in resistance as determined by outside air temperature. The PCM then messages the ambient air temperature data to the HVAC module, which then filters the temperature data and sends the updated temperature status through the Body Control Module (BCM) over the High Speed Controller Area Network (HS-CAN). The BCM (Body Control Module) in turn messages the ambient temperature data in degrees Celsius (metric) to the Instrument Panel Cluster (IPC) over the HS-CAN (High Speed Controller Area Network). When the Fahrenheit (English) display is selected by the driver, the IPC (Instrument Panel Cluster) converts the Celsius to Fahrenheit and displays the temperature in the message center.
The HVAC module is programmed to update the messaged outside temperature data at different rates depending on several criteria to prevent false temperature displays due to a condition known as heat soaking. Heat soaking is where the outside air temperature is hotter in the location of the Ambient Air Temperature (AAT) sensor than the actual outside air temperature.
When the sensed outside temperature rises, the display updates slowly at varying rates based on vehicle speed. When the sensed outside temperature drops, the display updates more quickly basically following the drop experienced by the AAT (Ambient Air Temperature) sensor.
This pinpoint test is intended to diagnose the following:
- Communication concern
- PCM concern
PINPOINT TEST AH : THE OUTSIDE AIR TEMPERATURE DISPLAY IS INOPERATIVE/INCORRECT
NOTICE: Use the correct probe adapter(s) when making measurements. Failure to use the correct probe adapter(s) may damage the connector.
AH1 RETRIEVE THE RECORDED DTCs FROM THE IPC (Instrument Panel Cluster) SELF-TEST
- Check for recorded IPC (Instrument Panel Cluster) DTCs from the self-test.
Are any DTCs recorded?
Yes
For DTC U0140:00, GO to Pinpoint Test AU Pinpoint Test AU: DTC U0140:00.
For DTC U0424:82, GO to Pinpoint Test BB Pinpoint Test BB: DTC U0424:82.
For all other DTCs, REFER to DTC Charts Instrumentation, Message Center and Warning Chimes.
No
GO to AH2.
AH2 RETRIEVE THE RECORDED DTCs FROM THE HVAC MODULE SELF-TEST
- Check for recorded HVAC module DTCs from the self-test.
Are any DTCs recorded?
Yes
REFER to Heating and Air Conditioning.
No
GO to AH3.
AH3 RETRIEVE THE RECORDED DTCs FROM THE PCM KOEO (Key ON Engine OFF) SELF-TEST
- Check for recorded PCM DTCs from the Key ON Engine OFF (KOEO) self-test.
Are any ambient temperature sensor DTCs recorded?
Yes
REFER to Computers and Control Systems Information.
No
The system is operating correctly at this time. The condition may have been caused by a heat soak concern.