What is the reason why the engine light does not illuminate during power-on self-check?
4 Answers
It is normal for the engine light not to illuminate during the power-on self-check because the engine light typically turns on when the car is not started and automatically turns off within 3-5 seconds after starting. Additional information: If the engine fault light remains illuminated while driving, it usually indicates an engine malfunction. Possible causes: The engine fault light often illuminates due to issues with the fuel emission system. When the fault light is on, try starting and turning off the vehicle three times, then observe whether the fault light remains illuminated upon restarting. If it stays on, promptly visit a service center for inspection.
When the engine light doesn't illuminate during power-on self-test, focus on the instrument cluster system. I've encountered this several times - the most common causes are damaged backlight or burnt bulbs in the dashboard. Loose connectors in the instrument cluster assembly can also interrupt signal transmission, basically poor contact. Another possibility is communication line failure between ECU and dashboard, like rodent-chewed wiring harness preventing self-test signals. The worst case is crashed engine control module, when the dashboard receives no command to illuminate warning lights. I recommend first checking instrument cluster fuses, and if okay, visit a repair shop promptly for diagnostic trouble code reading.
This is a common issue I encounter during car repairs, with the core problem being that the dashboard isn't receiving the self-check signal from the ECU. If you've confirmed other dashboard lights are functioning, first rule out a blown fuse. Next, consider whether the engine warning light's LED or circuit is damaged, which would require removing the dashboard for inspection. Pay special attention to checking if the communication line from the OBD interface to the dashboard is intact, as some owners may accidentally damage the wiring when installing aftermarket devices. Some vehicle models also experience cases of lost dashboard programming, requiring a system reflash. Here's a handy tip: if the tachometer works normally after ignition, it generally indicates the ECU is functioning properly, and the issue lies with the dashboard components.
When the engine malfunction indicator light fails to illuminate during power-on, it essentially indicates a failure in the indicator system. Based on experience, troubleshooting can be divided into three levels: The most basic is instrument cluster failure, such as a burnt-out bulb or damaged cluster assembly. The intermediate level involves wiring issues, particularly aging or cracked wiring harnesses between the engine compartment and the instrument cluster. The most critical issue is a communication breakdown with the electronic control unit (ECU), where the instrument cluster fails to receive the illumination command. It must be emphasized that this is extremely dangerous—this light serves as the monitoring system's eyes. Its failure to illuminate means you would remain completely unaware of actual malfunctions. There have been documented cases where owners missed turbocharger fault warnings due to a non-functional indicator light, ultimately resulting in engine cylinder scoring.
