Intake Air Temperature Sensor Testing

INTAKE AIR TEMPERATURE SENSOR OPERATION













OPERATION
- The intake air temperature sensor functions to convert the temperature of the air drawn into the engine to a voltage, and to input that voltage as a signal to the engine control module. The engine control module, based upon those signals, then corrects the amount to fuel injection, etc.
- The 5 V power supply within the engine control module is supplied, by way of the resistance within the unit, to the intake air temperature sensor, it passes through the intake air temperature sensor, which is a type of resistor, and is grounded as the engine control module. Note that the resistance of the intake air temperature sensor decreases when the temperature of the intake air increases.
- The intake air temperature sensor terminal voltage becomes higher when the resistance of the intake air temperature sensor increases, and becomes lower when the resistance decreases. Consequently, the intake air temperature sensor terminal voltage varies in accordance with the temperature of the intake air, becoming lower when the temperature of the intake air increases.

TROUBLESHOOTING HINTS
Because the intake air temperature of the intake air in the air cleaner, it indicates a temperature different than the temperature of the outside air when the engine is running.




INSPECTION
Using Scan Tool

HARNESS INSPECTION



STEP 1. Check for continuity in the ground circuit.
- Volume air flow sensor connector: Disconnected
OK: GO TO STEP 2
NG: Repair the harness. (A5 - 49)




STEP 2. Check for an open or short-circuit between the intake air temperature sensor and the engine control module.
- Volume air flow sensor connector: Disconnected
- Engine control module connector: Disconnected
OK: GO TO STEP 3
NG: Repair the harness. (A6 - 62)




STEP 3. Measure the power supply voltage.
- Volume air flow sensor connector: Disconnected
- Ignition switch: ON
- Engine control module connector: Connected
Voltage (V): 4.5 - 4.9
OK: STOP
NG: Replace the engine control module.

INTAKE AIR TEMPERATURE CHECK
1. Disconnect the volume air flow sensor connectors.




2. Measure the resistance between terminal (5) and terminal (6).




Standard value:







3. Measure the resistance while heating the sensor using a hair drier.
4. If resistance does not decrease as heat increases or the resistance remains unchanged, replace the volume air flow sensor assembly.