TTEC4848 Vehicle Electronic Controls- blog 2 on car test

Engine Electronic Control Systems

    On-car test

From these test we used TOYOTA 4A-FE engine to test Input sensors and Actuators On-car.

Throttle Position Sensor(TPS)

First we found the TPS of the engine, and checked this TPS is four pin type. We use voltmeter checked four wires and we know: Red- 5V ref voltage/ Black & white- Signal output/ Blue- Idle speed/ Brown- Ground. After we checked the voltage change when we open the throttle, and we turn the ignition on but not start the engine we half open the throttle we could read the voltage is 2.17V, than we fully open the throttle we read is 3.88V, also we slowly open the throttle from close position to fully open position and checked from the voltmeter, the voltage readings is slowly increase. It is mean this TPS in good condition.

Than we start engine and open the throttle position we could hear the different from close position to open position, the engine speed was increase. So we could know if disconnect the TPS and the ECU cannot know how many air from intake to engine so the ECU cannot put correct fuel to mixture.

Engine Coolant Temperature (ECT)

We found the ECT from my engine bottom and it is tow wire: White- Signal/ Brown- Ground. We use voltmeter to read the DC volts is 3.8V and this reading from the cold engine, than we start the engine and wait about few minutes when the engine warming up we checked the voltage again and we are reading is 0.45V. So it's mean the ECT works good and connection is good. Follow the work sheet we checked the ground coolant temperature sensor and we got the reading is 0.0085V less than 0.05V.

If bad connection of the ECT it will be give the ECU wrong signal,and the ECU would not made right signal to the other system, because the ECU cannot know the engine in which situation cold or warm.

Mass Air Flow sensor (MAF)

From this car we found the MAF sensor is hot wire type and it has five pin: Black- Battery/ Green- Ref. signal/ Yellow & Black- 5V from ECU/ Brown- Ground/ Blue- none, we know the green wire is signal feed back to ECU. 

In the test we use multimeter to check the Hz we were read is 0.2Hz, than we checked voltage is 0.6V, so we know it has good connection and in the good condition. Than we start the car when the engine is cold we read is 1.17V, after few minutes we step on the throttle to get quick, but just short acceleration of the engine. We record the increased reading on the meter: 2.3V.

Camshaft Position Sensor (CMP)

We found the CMP is tow pin type, it has tow wires and after use voltmeter checked we know: White- Ground/ Black- Signal.

We checked DC volts: 0.1-0.3V, AC volts:1-3.7V, Hz:100-160Hz(when accelerated 25Hz higher) and % Duty Cycle:75%(when accelerated we got same reading)

From this test we know the CMP is signal to the ECU, than ECU telling the coils when to fire. The information is critical, because an engine can only run properly if the spark plugs fire near the top of the compression stroke, and the computer would be unable to adjust the ignition timing to compensate for driving conditions without that information.