Why Is My Check Engine Light (MIL) On? How To Turn Off MIL Light?

If a fault occurs in the engine and the connected systems, the engine malfunction indicator light (MIL) or (Check Engine Light)  illuminates, informing the driver that there is a problem. When the ignition is switched on, the fault lamp always illuminates for inspection, the fault lamp goes out after the engine has started, if it does not go off, there is a fault in the engine. The only way to know why the malfunction (check engine) lamp is on, is to connect the vehicle to the diagnostic device. The parts cannot be changed and the fault detection cannot be made by prediction.

 

The main task of the engine malfunction indicator light is that the driver will notice the increase in harmful gases from the exhaust as a result of abnormal operation on the engine and fix it as soon as possible. The engine works perfectly thanks to the harmony and trouble-free operation of dozens of sensors,  actuators, electronic equipment and mechanical systems in the vehicle. In the event of a fault in any of these, the operation of the engine is impaired, the engine malfunction indicator light (MIL) illuminates.

Rarely, sometimes due to a instant and temporary problem, the fault lights may come on even though there is no abnormality in engine operation and performance. A short-term communication failure, non-contact cables, interruption of ECUs, etc. cause malfunction lamp illuminates. The system runs a logical test of these faults and checks whether they are repeated, which may require several trips, and if the fault is found to be absent, the system can automatically turn off the fault light. The vehicle must be connected to the diagnostic device in order to understand what is actually going on.

How To Turn Off The Engine Malfunction Lamp?

To switch off the fault lamp, connect the vehicle to the diagnostic device and clear the fault memory. The procedure for clearing the fault depends on whether the fault is permanent or temporary. This separation and quenching process is briefly described below.

Fault Lamp - Check Engine Light

When the engine fails, the fault lamp usually lights up in the form of a yellow engine. Fault lamp; Also called MIL (Malfunction Indicator Light). Sometimes the warning lamp may contain the text "Check Engine" in the symbol.

Features of Fault Codes (DTC)

When the fault codes are read on the device, details of the fault are given.

Trouble codes (DTC Trouble Codes), consisting of letters and numbers, can be seen from a table to see what it means. For example: P0100

Current DTC: Currently valid faults. Indicates that this fault is still present.

Pending DTC: The type of fault in which the fault has occurred but is still tested. The pending fault is passed to either history failures or current failures over time.

History DTC: History malfunction. This fault has occurred in the past and the fault code has been stored in memory, but does not continue. This fault can be cleared manually or the system will automatically remove the fault from the list screen over time.

Temporary DTC: Sometimes the fault is illuminated due to a instant non-contact cables or instantaneous situation in the electronic equipment, the fault does not recur again, this is called a temporary fault, which must be cleared by the computer (diagnostic device) and will not return. On some models, the ECU software automatically detects that this is a transient failure, for which the ECU monitors the engine operation in terms of hours, revolutions, number of travels; if not repeated, turns off the MIL light. On some vehicle models, the diagnostic software indicates that this is a permanent fault when clearing the fault log, and refuses to delete it, or tests whether the fault has been cleared immediately after deleting it, and if the fault persists, it returns the fault code.

Sometimes when you fix a problem, you turn off the fault lamp, for example; brake fluid low warning lamp illuminated, complete when extinguished. Tank cap not fully closed warning lamp illuminated, squeezes out, after a while indicator lamp turns off. Plugs out of an electronic component, plug in it.

Permanent Malfunction: This malfunction means that there is a non-transient and ongoing (continuous) malfunction. This means that this fault will not go away until it detects and fix the problem. In this case, the repair and replacement of the defective part is done first, then the fault memory is erased again, normally the fault memory is expected to be erased, if the fault does not come back, the problem is eliminated. However the road test must be taken or the engine should be run in various situations according to the type of the fault. Make sure that the malfunction lamp does not come on.

Why Malfunction Indicator Lamp Is On

In the event of an abnormal condition or malfunction of the engine, the engine malfunction lamp will illuminate, the sensors that most often illuminate the engine malfunction lamp; usually the lambda sensor or knock sensor. The lambda sensor switches on the fault lamp in the event of fuel-injection and air-fuel mixture problems and combustion efficiency problems. The knock sensor is more concerned with ignition failure.

Engine Malfunction Indicator Lamp Flashing

If the fault lamp in the shape of a yellow engine flashes, there is a serious problem with the engine runing, the engine control unit (ecu) will turn the light on and off, putting the engine in limp mode. Limp mode is an emergency strategy that the ECU uses to avoid damaging the engine. It tries to fix the operation of the engine, changing the ignition advance and injection timing, limiting engine speed, limiting engine power, neglecting gas demand. Sometimes stopping and restarting may cause this mode to cancel. Service is required as soon as possible.

Diagnostic Scan Tool: It is a system in which each brand develops its software specially for itself, reads the fault codes, details the fault code, identifies the possible causes of the faults and the parts to be checked and even includes instructions on how to fix them. The vehicle cable connector (OBD terminal) is universal type socket which connects the car and the scan tool.

What Is OBD and EOBD?

OBD means on-board diagnostics, this was first used by the automotive manufacturers in the US. E-OBD is the European version of the  OBD (Euro On-board Diagnose).

Logic of the system; If a fault or an abnormal condition occurs in the engine and this increases the exhaust emissions, warn the driver to have it repaired.