Make :: Toyota
Model:: 4A-FE
In this section i am going to be explaining the fallowing components.
MAP (analogue voltage)
MAF (analogue)
TPS (linear type)
ECT
IAT
Signal Name ..........MAP sensor( Anolog Voltage)
Volt/division/range 0.5V
Time/division/range 5 sec/ 500 ms
Draw the pattern below:
- When the map sensor was being tested at IDLE the voltage was 0.043V..
- The voltage increased when RPM was increasing putting the resistenc in the sensor low,this happens becouse there is a hot wire inside the MAP sensor that the ECU tries to keep hot
- When deselarating there is less air flow because the butterfly is closing. when there is less air Then the ECU is designed to put out less current to keep the wire hot.
Explain in detail an electrical fault that would make this unit operate incorrectly.
- A bad resistent voltage signal output in to the ECU,.
- As a bad earth at the sensor or a shorting wire from the sensor would give a wrong reading to the ECU ,
- If the voltage signal from the sensor to the ECU is incorrect could result in messing up the ignition timing , airflow and ,fuel mixer.
- Low input voltage to this sensor will be a major problem as if not enoffe voltage is put in to the sensor, it could couse the sensor to operate incorrectly because the sensor would not have the full 5 volts to send the appropriate signal back to the ECU
MAp sensor simple diagram
- the orange line determinds when the engine was given extra RPM ( at the start of the first hill) than normal ,then anather quick rev same amount of RPM.
- this is a well diagnosed pattern that show the increase in voltage and deceleration timming and pattern.
Signal Name ..........TPS (linear type)
Volt/division/range...0.5V
Time/division/range..5s
- This sensor is accurate to the throttle butterfly angle because the sensor is connector directly to the throttle body.
- Point 1: is were the car is at IDOL.
- Voltage at this point is 0.5V.
- The throttle is slightly open letting a slight flow of air in..
- Point 2: is were the quick acceleration was applying(2000RPM). also the voltage rises at this point.
- the throttle was released. (voltage starts decreasing)
- This happens quiet fast for one rev.
- in 5 sec I got 5 revs.
- At point 3 the throttle closes(idle) again the voltage returns back to 0.5V
- this reading is accurate and matches the TPS sensor specs. (liner type)
- Lag, or struggl in acceleration, and tough could occur if the carbon not good.
- The reading shows that the rising and declaration happens smoothly. This shows that the TPS sensor is sending a clear voltage to the ECU.
- The voltage reading to the ECU can also go wrong if the grounding on the sensor is crowded(rusted), or a loose connection.
Signal Name ..........ECT
Volt/division/range...0.5V
Time/division/range..5s
- The engine coolant temperature sensor resistance changes acording to engine coolant temperature. The sensor resistance decreases as the surrounding temperature increases. This provides a reference signal to the ECU which indicates engine coolant temperature on the dashboard..
- to course a problem in the reading sent to the ECU i made a faulty grounding.
- If a wrong voltage signal is sent to the ECU threw the output from the ECT sensor , the ECU would calculate the difference and make the mixture acorddingto the calculations.
- This could result in the car running richer or leaner..
- the reading shows us the voltage signal stated at the top and slightly decreased this is becouse the engine was slightly wamer.
Signal Name .........IAT (thermistor,air tempratuer)
Volt/division/range...0.5V
Time/division/range..5s
- Using the heat gun i had to cearfuly send hot air in to the sensor threw the throttle body.
- The sensor is able to sense the amount of hot air (the denseity) entering the engine, then send a voltage signal to the ECU from the output of the IAT, the ECU can tell the density of the air and mix the rite amount of fuel in to the mixture according to it.
- bad grouning at the sensor, dirty sensor, bad connection at the sensor to the ECU, or even high resistenc at the intake can result in wrong output voltage at te ECU and having a hard time in starting the engine in the morning,
- This could also effect fuel economy(richer mostly), poor engine running condition, loss of power, and flat spots in the fuel line..
