P009A - Intake Air Temperature / Ambient Air Temperature Correlation
Intake Air Temperature is monitored to allow the ECM to accurately adjust fueling and emission control systems as the temperature directly affects the air density. The Ambient Air Temperature Sensor can also be used by the ECM for fueling and emission control but it can also be used by other control systems for driver information and climate control.
Fault Code Explained
With the ignition switched on and the engine not running both these sensors should read the same temperature. The ECM has detected different readings from these sensors when they should be the same
If possible use a diagnostic computer to view live data readings for the sensors to establish which sensor is reading the incorrect value. Test the sensor supply Voltage and output signal.