Input Sensors and Actuators On Vehicle

Input Sensors and Actuators

Injectors

It is a good idea to check the voltage supply to the fuel injectors, when i tested it was 14.5 volts. If there was lower voltage than the battery, it could mean that there is a short creating resistance in the injector wires. This can affect how well the injectors respond.

Reference Voltage at TPS Sensor 

The purpose of the reference voltage to the throttle position sensor is so the sensor can work, 5 volts comes in and depending on the position of the valve depends on how much resistance is used before the sender to get a variable signal. If the reference voltage was not right, there could be possible shorts or damaged connections. This will increase resistance making  making the 5 volt reference voltage less sending incorrect signals back to the ECU

Ground at TPS Sensor 

I located the ground wire on the TPS sensor, back probed it and recorded a voltage reading of 0.008 volts. A good ground will usually read less than 0.05 volts. It is important to measure this because there needs to be a good ground for the sensor to work properly. If the TPS had a bad ground we would get incorrect signal readings sent back to the ECU resulting in poor running conditions.

Throttle Position Sensor Return/Output   


A TPS has a reference voltage, signal voltage and a ground. There is a potentiometer inside (linear)  or other type (switching) that only has lower and higher voltage. As the throttle, opens the resistance changes, changing  the signal voltage. When the car is at idle or throttle closed, there will be around half a volt. As the throttle opens up the voltage will increase until full throttle is reached and will have 5 volts on the signal. If there is any faults in the wiring or bad connections there will be a higher resistance effecting the signal voltage.






ECT (Engine Coolant Temperature) Sensor


The ECT has a resister in it that changes with coolant temperature. As the temperature rises the resistance gets lower. This allows a signal voltage to the ECU so it can determine what fuel to inject. The voltage will change the fuel injection, this is because when the engine is cold it will run more fuel, when hot the ECU will inject less fuel.

If there is bad connections there will be extra resistance making it hard for the ECT to tell the ECU exactly how hot the engine is, this will result in incorrect air/fuel ratio.