What's the reason for a car not performing self-check after power-on?
2 Answers
If a car does not perform self-check after power-on, it may be due to wiring or computer malfunctions. It is necessary to check whether there is an issue with the power supply to the engine control unit (ECU), followed by verifying if the ECU itself is functioning properly. Common reasons for the self-check light to illuminate: Sensor issues: Sensors include those for coolant temperature, crankshaft position, air flow, intake air temperature, oxygen levels, etc. When these sensors are damaged, have poor connections, or experience signal interruptions, the car's ECU cannot accurately obtain engine data, which may trigger the engine self-check light. Maintenance issues: Poor engine maintenance is the most common reason for the engine self-check light to illuminate. Vehicles have specific maintenance schedules, and if the owner does not adhere to these schedules, combined with poor driving habits, it can increase the operational burden on the engine.
I've been driving for over twenty years and have encountered several instances where the vehicle powers on but fails to perform a self-check, which is quite annoying. The most common causes are insufficient battery power or loose connections. Once in winter, I forgot to turn off the lights, and the battery drained completely. The next day, when I powered on the car, the dashboard was completely dark, not even a single light turned on. You also need to check the fuse box—there might be a blown fuse or poor contact in the ignition switch. If the ECU control unit malfunctions, it can also prevent the self-check. I simply use a basic multimeter to test the battery voltage—if it's below 12 volts, you'll need to recharge or replace it. Clean the connections to prevent rust and ensure they're secure—don’t take it lightly. Starting the car without a self-check might prevent the engine from cranking and affect the safety system's detection. Make it a habit to regularly test the battery to avoid such hassles.
