Fault phenomenon
    Last year in late December, is the coldest period of the year, a Toyota Dafa into my factory, requiring maintenance. According to the owner, the car recently started difficult, often to repeatedly start many times, take a long time to barely start the car, when the weather is particularly cold, according to the usual way to start the car, no matter how can not start, Let go of the water in the tank, put on hot water, only to start up the car. Owners and said, as long as the car did not cool down, the car's start performance is very good.
    Troubleshooting and troubleshooting
    According to the owners reflect the situation, we wait for the car to cool down, the water tank into the hot water to start the car, the purpose is to repeat the symptoms of failure, the results and the owner of the same situation; when we will start the car, found that The fault lights of the car are lit.
    Toyota Dajia Automobile 2.4L EFI engine and electronic control automatic transmission, set the cold start injector. According to the fault symptoms, the fault should occur in the start circuit, because the fault light, so start from the fault code check.
    The fault code is 22,41 and 43, the fault code means that the fault code 22 indicates that the cooling water temperature sensor signal is faulty; the fault code 41 is the throttle position sensor or its circuit fault And ECU failure; fault code 43 for the start signal is bad.
    More than three fault codes, of which 22 and 43 yards, and the car start performance, and 41 yards has nothing to do with the fault, and did not hear the owners of the problem of this reflection, it is suspected pseudo-code or old code. Clear the fault code, the idea of ​​launching a car road test, check the authenticity of the fault code, road test again after the extraction of the fault code, there is only the fault code 43, 22 and 41 code for the pseudo code or have been in the past but has been repaired But did not clear the fault code. The remaining 43 yards for the hard code, and the car with the current fault coincidence. According to the maintenance information, the emergence of 43 yards is the start circuit or start the motor and ECU fault; but according to the fault phenomenon, start the motor and ECU failure is very small, and start the circuit switch signal and cold start control circuit and Battery power failure and the possibility of failure, so a comprehensive inspection of these systems lines and electrical appliances.
    Check the battery voltage with Toyota special diagnostic apparatus, the voltage value is 12.5V, is normal. Check the ECU STA and the ignition switch ST1 feet between the line status, circuit diagram shown in Figure 1. Check the result is: shake the engine, with Toyota-specific diagnostic instrument to detect ECU STA pin and ignition switch ST1 pin voltage value is 0.25V; and the standard value should be 12V, indicating that the line somewhere ground short circuit, replace the line The
    Maintenance work so far, that failure can be ruled out, so start the engine, the car is still difficult, but improved, indicating that the fault is not completely ruled out.
    Toyota Dafang Automobile is set to have a cold start control system, so then in-depth inspection, remove the cold start fuel injector, and connected to the pipeline and plug the wiring harness; remove the starting motor on the start switch line, Ignition switch to ST1, found only one oil, then stop the fuel injection. According to this phenomenon, indicating that the cold start control circuit failure. Check the cold start control circuit and its electrical components.
    1, the detection of cold start injector. Unplug the injector harness connector, check the two plugs, injector conduction, and because of the test, the cold start injector oil spray smoothly, so you can certainly no problem with the injector.
    2, check the cold start temperature time switch. Place the ignition switch in the "off" position, unplug the temperature time switch of the wire connector, the time switch on the water to measure its resistance value, measured resistance value of 0, conduction, indicating good switch; detection STA and STJ terminal The resistance is ∞, no conduction.
    In order to further find out the point of failure, the STA terminal of the measurement switch and the STA terminal resistance of the ECU are 0, and the STJ terminal of the measuring switch and the STJ terminal of the ECU are ∞. The reason is that the circuit is broken and the wire is replaced. The car test, the car is very smooth, troubleshooting. Ask the owner, the original car had some time ago had been repaired, after the emergence of a cold start difficult trouble.
    The reason for the failure of the vehicle is that the STA's STA pin and the STJ pin of the ignition switch are grounded so that the ECU can not receive the STA signal. The ECU's self-diagnosis system outputs 43 yards, and the ECU's STJ pin and the temperature time switch are off, Set the cold start failure, so cold start difficult.