Why does the engine malfunction indicator light sometimes turn on and off?
4 Answers
It may be due to poor gasoline atomization and combustion efficiency when starting the engine cold, as the engine temperature is low. Engine malfunction indicator light intermittently turning on and off: This phenomenon occurs more frequently in winter, but generally requires no special attention. Within the first 5-10 minutes of starting, the engine malfunction light may flicker on and off, and the symptom will disappear once the coolant temperature normalizes. Vehicle self-diagnosis system: When a vehicle malfunction occurs, the malfunction indicator light on the dashboard will illuminate to alert the owner of potential issues. Pressing a button will display the fault code on the dashboard. Simultaneously, this fault signal will be stored in memory. Even after turning off the ignition switch, resolving the fault, or the indicator light turning off, the fault signal remains stored in memory to assist technicians in diagnosing the vehicle's problem.
I noticed the engine warning light comes on intermittently, mainly due to some electronic components developing intermittent faults. For instance, sensors like the oxygen sensor or intake air temperature sensor may send inaccurate signals under specific conditions, such as during cold starts or high-speed driving when signal fluctuations occur, causing the light to flash and then go off. Wiring issues are also common—oxidized or loose connectors can cause intermittent current flow. Sometimes the engine control unit misinterprets error codes, especially on bumpy roads, all of which can lead to the warning light appearing unpredictably. If the engine runs normally, it might just be a soft fault, but long-term neglect can affect emissions and fuel consumption. It's best to use an OBD scanner to check the codes and address them. I recommend regularly inspecting sensors and wiring to prevent minor issues from becoming serious.
As an average car owner, I find the intermittent illumination of the check engine light quite annoying. Once after rain, the light came on but disappeared when the weather cleared. A mechanic later explained it was caused by temporary short-circuiting due to moisture intrusion in wiring connectors. Minor fuel system issues often trigger this too - like a clogged fuel injector that only triggers warnings during aggressive driving. During normal operation, if the light comes on but the engine runs smoothly, it might not be serious, but I recommend watching for vibrations or unusual odors and getting the code scanned at a shop promptly. Don't delay, as a minor sensor fault could escalate into major repairs, increasing maintenance costs.
I have experience with this warning light flashing while driving. It's usually caused by aging sensors or signal interference, such as false alarms from the oxygen sensor at idle. Poor wiring connections are also a factor - loose plugs can make the light flicker on and off. If there's no change in engine power, it's mostly a soft fault, but you should promptly use diagnostic tools to read the trouble codes and prevent increased fuel consumption.
