Confirmed computer failure with Toyota Corolla timing light

1991 formula: Toyota · Corolla model: E-AE101 engine model: 4A-FE mileage: 68,000km

Bad idling and bad rush

Sometimes the engine check lamp lights up after starting the engine, causing problems such as idling malfunction and poor engine racing. I received a request from the user and wanted it to be repaired at the time of vehicle inspection and received it.

Engine check lamp self diagnosis

According to the result of the inspection, since the engine check lamp was lit, I decided to see the self-diagnosis. If the Te1 terminal and the E1 terminal of the diagnosis and connector were short-circuited and the ignition switch was turned on, the lamp remained on but when the Te1 terminal was opened and the ignition switch was turned on, the lamp did not light up It was.

Next, although I turned the starter, I did not teach it easily, but as I continued to turn it, the engine check lamp lights up, the engine started and I was able to check the symptoms the user was told.

From the above results, it is suspected that the engine computer is defective because it does not display the diagnosis or code, and the engine starts after the engine check lamp lights up.


Confirm by manual

If you purchase the manual and confirm it, since there is a backup function in the engine computer, if you check the contents, if an error occurs in the EPU in the engine computer, the backup state is entered, the diagnostic code is not displayed, the ignition timing is It was found that BTDC 5 ° (position 5 ° before top dead center of piston) is fixed.

When the timing light ignition timing was actually confirmed, it was judged that it was caused by the engine computer, because it was idling and the ignition timing displayed BTDC 5 ° (position before 5 ° before top dead center of the piston) even if it was idle did.

I exchanged the engine computer and finished the trouble


Diagnosis code

  • When an abnormality occurs in the signal from each sensor, the engine control computer detects an abnormality signal and lights the check engine warning lamp in the combination meter to inform the driver. Also, the abnormal part is stored in the computer, the warning lamp blinks when the Tei terminal in the diagnostic connector is short-circuited and the IDL contact is turned ON. Inform the operator of the abnormal item according to the number of blinks (code number).
  • The test mode method which greatly improves detection accuracy compared with the conventional diagnostic function is adopted. As a result, detection precision such as signal instantaneous interruption due to defective connectors, disconnection of starter signal, speed sensor signal, etc. due to connector failure which was difficult to detect by the conventional diagnosis is improved, improvement of accuracy of diagnostic diagnosis work and simplification It was.

  • Diagnosis code and diagnostic content


Failsafe function

If an abnormality occurs in the input signal from each sensor and it is possible that engine malfunction, catalyst overheating, etc. may result if control is continued with the abnormality signal as it is, using the standard value that the microcomputer considers 100 million Continue control or stop the engine.

Fail-safe function when vehicle abnormality occurs

  • In case of intake pipe pressure signal abnormality (vacuum sensor)
    If an abnormality (disconnection or short circuit) occurs in the input signal from the purse sensor, the air-fuel ratio will be shifted and the engine will be out of order. In this case, shift to the backup mode to fix the ignition timing and fuel injection time to a fixed value, and make it possible to run.
  • When ignition signal abnormality (IG coil disconnection)
    If abnormality occurs in the ignition system, such as disconnection of the ignition coil, overheating of the catalyst may be caused by misfire. Therefore, if ignition confirmation signal (IGf) from igniter is not input for two consecutive rotations, it is judged that the ignition system is abnormal, and fuel injection is stopped.
  • Water temperature signal · intake sound signal abnormal (water temperature sensor · intake air temperature sensor)
    When an abnormality (disconnection or short circuit) occurs in the input signal from the water temperature, intake air temperature sensor, the air fuel ratio becomes excessive or dilute, and the engine malfunctions during engine stall or cold. In this case, control is carried out by fixing to the standard value of water temperature 80 ° C and intake air temperature 20 ° C.
  • Engine computer backupShould an abnormality occur in the CPU in the engine control computer, control should be performed at the specified fuel injection time and ignition timing according to conditions such as the starter signal and the ON / OFF of the IDL contact of the throttle position sensor It makes the state possible to run. At the same time, the warning lamp lights up to inform the driver.Diagnosis is not displayed during backup operation. In this case, do not short-circuit the Te1 terminal and do the ignition timing (fixed at BTDC 5o °).

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