3-2604/14/2009NP10-V8JLR: AJ133 5.0-Liter DFI V8 EngineTechnical Training
Ambient Air Temperature SensorEngine Management System
AMBIENT AIR TEMPERATURE SENSOR
The ambient air temperature (AAT) sensor is located in
the underside of the LH exterior door mirror. The sensor
is an NTC thermistor – the element resistance decreases
as the sensor temperature increases, which produces a
low signal voltage.
The ECM supplies the sensor with a 5V reference volt-
age and ground, and measures the returned signal volt-
age as an outside temperature.
The AAT signal is used by the ECM for a number of
functions including engine cooling fan control and A/C
compressor displacement control.
The ECM also transmits an ambient temperature mes-
sage on the high speed CAN bus for use by other control
modules.
NOTE: If there is a fault with the AAT sensor, the ECM
calculates the AAT from the temperature inputs of the
IAT sensors. If the AAT sensor and the temperature
inputs of the IAT sensors are all faulty, the ECM adopts a
default ambient temperature value of 20°C (68°F).
Failure Mode
• Default value of 20°C (68°F)
PinFunction
Pin 1 5V supply
Pin 2 Ground
