ECT - Coolant temperature sensor

• Measures the temperature of the coolant in the system and feeds it to ECU which uses this data to give you good, smooth driving while the engine is cold. A cold engine will have a high voltage output and as the engine gets warmer the voltage output sent to the ECU will decrease.
• Measured in DC volts
• Average readings are 2.5V on a cold engine and 0.4V on a warm engine
• Effects fuel injection and ignition timing

TPS - Throttle position sensor

• Important to ensure economic and smooth driving and can be adjusted to increase operation. It supplies information to the ECU about the position the throttle is in. Signs of a bad TPS can be Hesitation while trying to accelerate, Random stalling of the engine and surging idle
• Measured in DC volts
• Average readings are 0.5V closed throttle and 3.8V open throttle

CKP - Crank position sensor

• Determines the position and rotation off the crank. The ECU uses this information to control fuel injection timing and ignition timing
• Measured in AC volts and Hertz
• Average readings are 0.5V / 0.027KHz at idle and 1.5V / 0.086KHz at 2500 RPM

MAP sensor - Manifold absolute pressure sensor

• Measures the change in vacuum. The ECU needs to know this to calculate how much fuel to inject, when there is high vacuum in the manifold the throttle is wide open and all the air is being used so the computer adjusts the fuel mixture by holding the injectors open for a longer period of time, feeding more fuel to the engine as more air is flowing through. When there is low vacuum there is alot of air in the manifold so the ECU doesn't need to hold the injectors open for long (Usually during Cruise mode)
• Affects the injectors
• Measured in DC volts
• Average readings are 1.4V at Idle vacuum and 5V at no vacuum or engine off

IAT - Air temperature sensor

• Measures how dense the air is
• Measured in DC volts
• Average readings are 2.4V on a cold engine and 2V on a warm engine

Fuel injector

• Measured in duty cycle
• Average readings are 3.7% at idle and 30% under acceleration

Idle Air Control

• Measured in duty cycle
• Average readings are 64% at idle and 32% under acceleration

VSS - Vechicle speed sensor

• Sends electrical pulses to the ECU, When the vechicles speed increase the pulse increases.
• Measured in frequency (HERTZ)

Open loop circuit:
Is when the O2 sensor is not functioning so there is no change in your air to fuel ratio. This is used when your engine is cold as the ECU wants to richen the mixture and doesn't want the O2 senor trying to lean it out. The O2 senor operates when it reaches 300 degrees C. Until then it is a open loop circuit. Another condition where open loop circuit is used is when your engine is under hard acceleration. Again the ECU wants to make the engine run rich and doesn't want the O2 sensor trying to lean out the engine to meet the 14.7-1 Ratio as you need as much power as possible from the engine until you back off the accelerator.

Closed loop:
Is when the O2 sensor is up to its 300 degrees C operating temperature and controlling the ECU telling it to either Richen the engine or lean it out. So under normal driving conditions your system operates at closed loop, letting the O2 sensor give feedback to the ECU on wether to make it run lean or rich.