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.

WS6 Oxygen Sensor On Vehicle

Oxygen Sensor On Vehicle 

The oxygen sensor in the Honda Accord that i used, was located on the headers on the exhaust manifold. It was a Zirconia switching sensor type with one wire.

2500 RPM

I back-probed the O2 sensor wire with a pin and connected it with an oscilloscope. It produced a AC pattern. The range is .9 volts to 0 volts. If the signal is not cycling normally, the signal will stay roughly this is because the system is still in open loop or has a leak o some sort. 

Idle RPM


The voltage range 0.008 volts to 0.9 volts. After calculations, the average voltage i worked out was 12 volts. The signal will show either a constant rich or lean situation or less cross counts.

O2 Rich 


The sensor voltage when as high as 1 volt. If its not normal we may see that we don't get the high part for as low or it may cycle, this will give as faulty signals.

WS5 Scan Tool Diagnostics

Scan Tool Diagnostics

Using a scan tool on a Honda Accord I recorded the follow live data.

Engine RPM = 770 

Throttle Angle = 9.4 - 9.8

Engine Coolant Temp = 78 degrees C

Intake Air Temp = 25 degrees C

Fuel Inj opening pulse = 2.35 ms

Transmission select position = P/N

Vehicle Speed = 0 Km/H

Oxygen Sensor =  .55 v

Air conditioning = OFF

Exhaust Gas Recirculation = 1.27 v

Fuel Evap = Off

Malfunction Indicator Light = Off

Live data is very important and if you know what the components readings should be then it can help you find faults in the engine.

Using the scan tool, I tested for any trouble codes and found none. To test me, my lecturer created a fault and the hood. So i tested for any trouble codes with the scan tool and found code 12 (MAF). Looking at the engine i found the MAF sensor and fixed the fault by plugging it back in. I then cleared the codes and tested again. No fault codes.

Scan tools are a big help in finding faults in a engine, but they don't fix the problem. We still need to do other tests as well such as back-probing and volt drop test do fully understand whats going on. 

WS2 Flash Codes

Flash Codes

I tested a Honda accord. We located the ECU Diagnostic Plug which was on the front passenger side down by the door. We fused the to pin plug and used a jumper wire to bridge them. Then turn the ignition on and the engine check light started to flash. By watching the engine check light we got code 3, 7 and 10.

By looking in a Manuel we found out what systems had been affected.

Code 3 = Map Sensor

Code 7 = TPS Sensor

Code 10 = IAT Sensor

Now knowing what systems have been affected i did a visual inspection of the engine and found the map, TPS and IAT sensors were unplugged. 

After plugging the affected components back in i cleared the codes by unplugging the negative lead to the battery for about 20 seconds, and then rechecked the codes. No codes came up.

Without these components the ECU wouldn't know whats going on so the cars performance would be very poor.     

WS1 Petrol Fuel Injector Testing

Petrol Fuel Injector Testing 

I tested the injectors on a Toyota 4A-FE. I used a stethoscope to listen to the taping of the injectors. They sounded sharp how the supposed to sound. 

I checked the battery voltage when the engine was at idle and recorded 13.9 volts which is good. The injector voltage is as follows.

Cyl 1 = 13.8v

Cyl 2 = 13.8v

Cyl 3 = 13.8v

Cyl 4 = 13.8v

With the engine idling i hooked up an LED tester to the ground wire of the injector. All injectors worked.

With the engine still at idle i connected a multimeter and set to duty cycle. My readings below.

Cyl 1 = 98.7 %

Cyl 2 = 98.7%

Cyl 3 = 98.8%

Cyl 4 = 98.7%

Accelerating the engine slightly the readings changed 

Cyl 1 = 80%

Cyl 2 = 79%

Cyl 3 = 81%

Cyl 4 =  80%

Changing the multimeter to Hz and with the engine at idle i recorded the following.

Cyl 1 = .014 Hz

Cyl 2 = .015 Hz

Cyl 3 = .017 Hz

Cyl 4 = .015 Hz

Accelerating the engine slightly the readings changed 

Cyl 1 = .026 Hz

Cyl 2 =  .029 Hz

Cyl 3 = .028 Hz

Cyl 4 = .026 Hz

Using this formula {Pulse width ms = (% Duty cycle/100)/Frequency} i calculated the pulse width for each injector. 

Time at idle (ms):

Cyl 1 = 8.5

Cyl 2 = 8.4

Cyl 3 = 6.64

Cyl 4 = 7.53 

Time when Revved (ms):

Cyl 1 = 7.69

Cyl 2 = 7.5

Cyl 3 = 6.55

Cyl 4 = 7.64

In Conclusion i think pulse with is more accurate way to test injectors because we can see how long the are opening in seconds, much easier to see rather than using Duty cycle or HZ.

  

WS4 Fuel Pressure and Flow (Petrol only)

Fuel Pressure and Flow

We connected up the fuel pressure gauge and tested the flow of the fuel. With the key on but the engine off i recorded 35 PSI. With the engine now turned on and running at idle it was still the same 35PSI. I use a special clamp on the fuel line but only for a short time and recorded 87PSI.

WS7 Exhaust Gas Analysis (Petrol Only)

Exhaust Gas Analysis 

I tested a couple of cars with the Exhaust Gas Analyzer, the first car was given mixed reading and found out the car had a exhaust leak which gave the O2 sensor a high Oxygen reading. The next car i tested the results follow.

Carbon Monoxide (CO) = .007
Hydrocarbons (HC) = 25
Carbon Dioxide (CO2) = 0
Oxygen (O2) = 207.9

When the engine was cold the the engine is running rich, this is why the HC is very high, (unburnt fuel). Also the CAT isn't working yet as the engine is not at running temperature. The engine is still running in open loop making it rich, this makes more CO.

CO = 1.9
HC = 180
Co2 = 13.3
O2 = 1.42


When the engine had warmed up i did the test again. The engine is now in closed loop and runs leaner. This leaves less HC in the exhaust and more CO2 because the mixture is burning properly. CO goes down because of good combustion.

CO = 1.51

HC = 130

Co2 = 13.8

O2 = 1.36

Next when ran the engine at 2500 RPM, and recorded the readings. It burned efficiently less air is left over because of good combustion.

CO = .6

HC = 73

Co2 = 144

O2 = .65

At idle again, we sprayed in CRC to run a rich mixture. HC rises in the exhaust because of more fuel to burn. CO goes up from incorrect burn and CO2 goes down. Less oxygen is left over because we have replaced it with extra HC.

CO = .8

HC = 115

Co2 = 14.2

O2 =  1.14

At idle, i created an vacuum leak and the engine and recorded my results. With a lean mix, HC goes right down, because of less fuel. In turn O2 goes up because less of it is used up to burn the fuel. CO2 goes up Because the burn is good and CO goes down.

CO = .2

HC = 75

Co2 = 14.5

O2 =  1.5

Snap Acceleration, CO goes up because of rich mixture not burning properly. CO2 goes down from poor combustion. HC goes right up because the injectors are spraying longer and O2 goes up from opening the throttle.

CO = 2.1

HC = 2000

Co2 = 9

O2 =  3.6

I disconnected one spark plug wire and grounded it with a jumper wire. This causes HC to rise because of no injection in one cylinder.

CO = 2.1

HC = 3294

Co2 = 8.2

O2 =  7.83

Summary


A catalytic Converter connects bad gases coming out of the car into friendly ones, thus HC, CO2 and CO will go down but the oxygen level will rise because the CAT is changing some of the gases into more oxygen and water.

The CAT becomes effective usually around 400 - 600 degrees F

WS8 Primary & Secondary Ignition Patterns

Primary Voltage Patterns

I set up a ignition oscilloscope to view the ignition patterns. The pattern is normal, the 200 volt is caused by the windings. The burn voltage is 35 volts, this is because it takes lots to start of but not so much to continue.

Primary Ignition 

Cyl 1         Cyl 2         Cyl 3         Cyl 4  

200v         200v          200v         200v           Firing Voltage

35v            35v           35v            35v            Burn Voltage

1.7ms        1.7ms        1.7ms        1.7ms         Burn Time

5.4ms        5.4ms        5.4ms        5.4ms         Dwell Time

The pattern shows us the dwell time, the voltage at ignition, burn time and voltage. This can show the spark is working.

Secondary Voltage Patterns

I set up the ignition oscilloscope to test the secondary windings.

The pattern looks good, i can see that the dwell time seams long and the firing voltage is very strong.

Snap Acceleration 

Cyl 1         Cyl 2         Cyl 3         Cyl 4  

  8               8                8                8           Firing Voltage (KV)

  .6              .6               .6               .6          Burn Time (ms)

 1815        1815         1815          1815        Snap Acceleration

This show that the Firing Voltage becomes higher and the Burn Time is lower.

Next i disconnected one spark plug lead and shorted to the engine using a jumper wire.   

Started the engine and let it idle, only for a short time. These are the results.

Cyl 1         Cyl 2         Cyl 3         Cyl 4  

  3                3               3               3           Firing Voltage (KV)

 1.5             1.5            1.5            1.5         Burn Time (ms) 

Spark Tester

Cyl 1         Cyl 2         Cyl 3         Cyl 4  

  2                2               2                2           Firing Voltage (KV)

  1                1               1                1         Burn Time (ms)