Make :: Toyota
Model:: 4A-FE
1.0 Locate Oxygen Sensor
1.1 Locate an oxygen sensor on your vehicle. Describe where it is located:
- THe oxygen sensor is located in the exhoust manifold, before the catalytic converter.
- This sensor is bolted directly into the exhaust to measure the amount of oxygen exciting the engine.
- This sensor has 3 wires.
1.3 Record the colors for each of the wires at the sensor side of the connector (not the ECU side of the connector). Then list the use of the wires. Usually a black or blue wire will be the O2 sensor signal, Grey may be the sensor ground. Heater power and ground are often white. But there may be other colors..
Colour Use or Purpose
White(Blue) Output wire.
White Back to ECU wire.
Black O2 signal wire.
Ground Body is the ground
1.4 What type of Oxygen Sensor is this? (tick one)
- Zirconium oxygen sensor
2.0 after probing the Oxygen Signal Wire with a pin and connect to an oscilloscope. Check that you are connected to the Oxygen sensor signal: Run the engine and check that you are
seeing a signal. Connected OK
Graph below is when the rpm is reved up to 2500.
- the higyest voltage reading was- 0.8V
- lowest voltage point? -0.4V.
- the average voltage reading was calculated by the ossylescope 0.7V
- in 10-seconds there are 2 Cross Counts
3.6 If the signal is not cycling normally, describe what the signal
does:
- The signal is working properly, if it is not, the engine could be running ruff and sluggish..
- YOu will be able to feel the uneven amount of fuel being burnt...
4.0 Watch and Record Oxygen Signal pattern at Idle rpm. Let the engine warm up and enter closed loop so you see a normal cycling pattern. You may have to hold the rpm about 2500 for half a minute to go into closed loop. Then let the RPM come down to idle.
4.1 Freeze your pattern and draw or photograph it onto the graph below: Note the voltage and time per division or scale next to the graph.
- the voltage goes up to 0.802V
- the lowest voltage reading is 0.024V
- the average voltage reading i got was 0.022V
- in 10 seconds there were 2 Cross Counts
- Would be cross counting a lot more the voltage reading will be jumping up and down more than usual.. wouldnt be a smooth flow down..
5.1 Freeze your pattern as it goes rich and draw or photograph
it onto the graph below: Note the voltage and time per division
or scale next to the graph.
- the higest voltage increased at 2500 RPM was O.874V.
5.3 If this signal is not going high normally, describe what the signal does?
- This means that the oxygen sensor is sending a signal to the ECU threw the output wire,this signal is telling the ECU to put in more fuel in to the mixture because the engine is struggling to run,this happens quick..
on smooth acceleration at 3000RPM let the acceleration drop suddenly. when declelerating the voltage goes below 0.2V and the engine goes leaner. the result is recorded below
The lowest voltage that the sensor voltage whent was -0.002V
6.2 If this signal is not going low normally, describe what the signal
does:
- This means the sensor is not adjusting to the changes happening (maybe not quickly enough).
- It cannot calculate the pressuer changing. so the signal goes wrong.
7.0 Measure the Response Time of the sensor. You want to know
that the sensor can respond quickly to changes in the exhaust gas.
The best way is to do a sudden acceleration, freeze the pattern, and
measure how long it took the sensor to go from lean to rich.
7.1 Freeze your pattern as it goes suddenly rich from a lean
condition and draw it into the graph below: Normally you want
the voltage to go from below 0.2V to above 0.8V. in less than
100 ms. Note the voltage and time per division or scale next to
the graph.
- This oxygen sensor seems to be working fine under the manufactures standers. .
- The changes accordingly and quickly under the various kinds of conditions, and under load. .
- It is a good thing that this sensor adjusts to the changes smoothly and efficiently.
- Yet this could still be a bad point because if there is a air leak in the intake manifold or a small hole in one of the housing in the intake hoses, or even a loose wirering giving the ecu a sightly wrong reading, the oxygen sensor will adjust to changes and get the engine to a smoother running condition.
- As electritions its our job to find these faults and fix them , (not by removing parts and fitting new ones but by checking for faults and referring to the manual).
