WS3 IAT

General Lab Scope


Signal Name IAT
Volt/division/range 2V
Time/division/range 10 ms


Draw the pattern below:

Explain the operation of the sensor or device using the Graph:
( Use arrows at different points, and describe what happens there)
Arrow A zero voltage 
Arrow B when the engine was cold voltage about 0.9 V 
Arrow C when the engine warmed up after zero second time the voltage was almost zero volt
Arrow D voltage continue dropping


Explain in detail an electrical fault that would make this operate incorrectly
If the IAT resistance is high, when the engine heated up it will have the return voltage signal wrong to the ECU. ie: The resistance drops as the temperature increase.


Explain why this condition would cause this unit to malfunction/Use mathematical equatios to back up your explanation
This unit will malfunction as resistance in high temperature is high and the return voltage signal is will be high too, therefore ECU reads this high voltage and determine the condition of the engine as cold.
Calculate : The ECU sends a reference voltage of 5 volts and gets the return voltage in represent to the voltage drop and then determine condition of the engine.
ie: If the variable resistor is R2 = 2500 ohms Ref V = 5 V
R1 = 1000 ohms then the total current I = V/R = 5/2500+1000 ohms = 0.0014 Amps
So the voltage drop will be V = IR = 3.5 V
Then the signal voltage is 5 - 3.5 = 1.5 V
therefore the ECU will determine the amount of fuel needed for the condition of the engine. If the resistance increase in the sensor ground side, then 3.5 V drop will .


Using the grah on the previous page (use different color) draw the pattern that this unit would give with this falt decrease as well so ths will effecthe function of the sensor and ECU will recive wrong sgnal and make wrong adjustment to PWM.


Explain how this condition would affect the operation of the vehicle?
On the graph not much changing because the engine was warmed .