Symptom: Toyota Corolla car equipped with 3S-FE engine, the car in the course of the occasional turn off the phenomenon, but can immediately start after the flame, but this time the engine is turned off for no reason to stop.
    Troubleshooting: after the car check results are as follows: 1. engine start without high pressure fire; 2. engine fuel injection nozzle can not measure the fuel injection pulse; 3. open the ignition switch, the engine failure warning light does not light (normally open Ignition switch, the engine fault light should be lit. After the engine starts the electronic control unit on the electronic control components for 4 ~ 6s self-test, to confirm the fault when the fault light is always bright, no fault when the fault light goes out). Taking into account the car ignition and fuel injection are directly controlled by the ECU, it is likely that the ECU lacks the operating voltage and can not work due.
    First check ECUEFI insurance, insurance without burning phenomenon. With a dedicated engine fault detector for testing, detector display no communication links. With a short connection to connect the diagnostic plug TE1 feet and E1 feet, to manually read the fault code, fault light is still not bright. In order to prevent E1 feet off bad, directly to the TE1 feet ground, fault lights did not respond. The owner reflects the fault light before the repair is good. This is more sure that the engine does not fire is caused by the ECU does not work.
    Find all the power lines BATT, + B, + B1 and all ground lines E, E01, E02 of the ECU, as shown in the figure, are found to be normal. We had to remove the ECU shell, its internal components for testing. Measured by the input line of fire, the cable can be sent to the ECU internal, pin no problem, and its internal components are not significantly burned, open welding phenomenon. In order to further determine the quality of the computer, we have to replace the ECU assembly comparison test. The replacement of a normal driving the same model on the ECU after the start of the test, still can not catch the fire. And the car ECU installed on the normal car, the engine can start the fire once, and the engine fault detector can communicate with the ECU, the engine conditions are normal, indicating that the car computer is intact, then the reason out Where?
    To this end, had to press the circuit diagram of the lines carefully "inventory." When the throttle valve operating voltage is detected, suddenly light up. The working voltage is not even 5V, only less than 0.7V voltage. It can be seen from the part of the circuit diagram, the intake pressure sensor, throttle opening sensor and CO concentration regulator variable resistor three share a power cord, the power regulator sent by the ECU, the normal value should be 5V. Replacement ECU comparison experiment has been determined ECU is normal, then it should be able to send 5V normal voltage. Must be on the line somewhere there is a short circuit caused by the voltage drop on the line is too large. Unplug the ECU plug, unplug the throttle position sensor plug, measure the throttle position sensor harness side line 4 (working power) to ground resistance, found less than 1Ω, abnormal value. Unplug the intake pressure sensor plug and measure the harness side line 3 (working power) to ground resistance and find that it is also only 1Ω. Check the CO concentration regulator variable resistor, pull out the variable resistor plug, wire harness side line 3 to ground resistance, found with the harness shaking its resistance sometimes infinite, sometimes 0. This shows that there may be a problem with the wiring harness of the CO concentration regulator.