WS5 Scan tool diagnostics

1999 Mazda Capella

No faults were indicated by the scan tool, so faults were created by Lecturer Steve.

After faults were created; vehicle was scanned again.

New faults were found as follows:

Comparing the value data before and after the faults:

-IAT temperature was originally 24.21, now 19.85 degrees Celsius

-MAF voltage was originally 1.88v, now 0.00 volts

When inspecting the engine bay, the IAT and MAF sensors were found loose or unplugged.

Both sensors were reconnected.

Scan tool was used again after sensors were reconnected, and these are the results.

The readings returned to normal.

Without knowing these parameters, it is possible to not know if there were any faults at all since the scan tool doesnt always pick up the faults. But by comparing the data from the different parameters, it is possible to find a fault if the scan tool doesnt pick any up.

WS4 Fuel Pressure and flow (petrol only)

Attach fuel gauge, briefly turn on key then turn it off. Check for fuel leaks.

No leaks.

Measure the fuel pressure with the key on, engine off.

284 kpa

Measure the fuel pressure engine edling. Watch the pressure for a couple minutes.

260kpa

When idling, use special tool to clamp the fuel return line.

500kpa

When idling, disconnect and plug the vacuum line to fuel pressure regulator.

300kpa

Turn off engine and watch the fuel pressure for 5 mins. Record residual.

250kpa

Read fuel volume. Record volume pumped in 15 seconds. Normal results around half a litre.

2.2 litres in 15 seconds

Its important to know the vehicles fuel pressure/flow so that you know whether the car is running at its optimum condition. Otherwise a faulty fuel pressure regulator maybe sending incorrect data to the ECU, and in turn several faults may incur in your vehicle. i.e: engine constantly running rich, or combustion chamber being flooded with gas. Emissions would be extremely high.

WS3B

WS3A Lab scope

Engine: Toyota 4A-FE

Signal name: Crankshaft Position Sensor

Volt/division/range: 2v

Time/division/range: 20ms

1. At this point, the sensor is directly in between the crank teeth giving a neutral magnetic force, and thus reading 0v.

2.As the next crank tooth approaches, the magnetic field starts to get stronger again, so the voltage reading starts to get stronger.

3. At this point the tooth is at its closest point with the sensor, and the magnetic field is at its strongest.

4. As the tooth continues rotating forward, it passes the sensor which sudddenly collapses the magnetic field, inducing a back EMF

If the sensor were damaged for any reason, or if it had faulty wiring or a bad ground connection, it wouldnt work properly. Also if there were any interference in the sensor lines, it could cause too much resistance, and therefore get an incorrect reading.
This is important because V=IxR. So if the resistance were too high, the voltage reading from the sensor would be far off what the actual reading should really be. The resistance could also be consuming so much voltage so the voltage reading could be far less than it actually is.

The blue line indicates what the readings may be if the sensor was faulty.
As the voltage is very high, it could possibly be a only a short time before this sensor would open circuit.


















Engine: Toyota 4A-FE

Signal name: Camshaft Position Sensor

Volt/division/range: 2v

Time/division/range: 50ms

The Cam position sensor is very similar to the crankshaft position sensor, so the tests will be similar also.

1. At this point, the sensor is directly in between the cam teeth giving a neutral magnetic force, and thus reading 0v.

2.As the next cam tooth approaches, the magnetic field starts to get stronger again, so the voltage reading starts to get stronger.

3. At this point the tooth is at its closest point with the sensor, and the magnetic field is at its strongest.

4. As the tooth continues rotating forward, it passes the sensor which sudddenly collapses the magnetic field, inducing a back EMF

If the sensor were damaged for any reason, or if it had faulty wiring or a bad ground connection, it wouldnt work properly. Also if there were any interference in the sensor lines, it could cause too much resistance, and therefore get an incorrect reading.
This is important because V=IxR. So if the resistance were too high, the voltage reading from the sensor would be far off what the actual reading should really be. The resistance could also be consuming so much voltage so the voltage reading could be far less than it actually is.
The blue line indicates what the readings may be if the sensor was faulty.
As the voltage is very low, it would send the wrong data to the ECU, which could induce more faults.

Engine: Toyota 4A-FE

Signal name: MAP sensor

Volt/division/range: 1v

Time/division/range: 500ms

a) Engine is idling. There is more vacuum so less voltage present. 1.8v.

b) Engine accelerating & drawing in more air so voltage starts to increase.

c) Voltage peaks and starts to decelerate.

d) Voltage drops even further as Manifold pressure increases.

e) Voltage returns to base voltage.


When the throttle opens up, the pressure inside the manifold is lost, and now has Lambda 1 or atmospheric pressure. Relying on the graph results, we see that the voltage on this MAP sensor increases as the pressure is lost, and voltage decreases as manifold pressure increases.
If there were a fault in this sensor, i.e: resistance in the signal wire etc. its possible that the voltage reading would become much lower than showed on the graph. A side effect of this would that the engine could be running leaner than needed.

Engine: Toyota 4A-FE

Signal name: MAF sensor (analogue)

Volt/division/range: 1v

Time/division/range: 500ms

1. At 0.00v, the acceleration begins and voltage rises.

2. The voltage increases because as the engine accelerates the throttle opens and air is travelling through the air intake. Air passes through the MAF sensor cooling the hot wire, so the ECU inputs more current to the hot wire to keep its temperature.

3. As the engine decelerates, there is less air passing through the MAF sensor, so less current is needed to keep the hot wire hot.

This MAF sensor is working fine. If there were any problems with this sensor, there would be no voltage reading, or if there were too much resistance, the voltage reading would be lower than the actual reading, as indicated in the sensors before this.

WS2 Flash codes

Flash codes

Experiment was performed on a Toyota 4A-FE engine.

Using the workshop manual follow the procedure to extract the codes, explain briefly what is the procedure:

In the diagnostic panel, I bridged the "TE1" & "E1" terminals.

The engine light flashes 'x' amount of times to indicate what the fault is.

e.g: for fault 12, the engine light will blink once, gap, then twice.

1 _ 2. Put them together and you have the number 12 etc.

Results are recorded as follows.

Code number System affected Condition described

12 G, N.E signal Rectified via 22, 31, 41

22 Water temp. Loose connection

31 Vac. sensor Loose connection

41 TPS Loose connection

Visual inspection to find the fault

Fortunately, with these faults that were identified all I had to do was just look for the component. i.e TPS, just look for the throttle and inspect the TPS.

Repair fault

Three sensors were loose or disconnected and all I had to do was reconnect them.

By rectifying 3 faults, the "G N.E signal" fault was also fixed.

Once I was sure all loose connections were tightened, I shut off the engine, disconnected and reconnected the battery and began the flash code test again to see if there were any outstanding faults.

The result I got was 1. 1 = Normal.

If the vehicle was to operate without the faults being rectified, the engine wouldnt operate correctly, and likely to damage the engine seeing that the TPS, Vac sensor, and water temp sensor werent operating. It would most likely be un-economic, and/or overheat.

Wiring up Ignition Systems

Standard Single Tower Coil