Why does the fault light come on after vehicle inspection?
4 Answers
During the vehicle inspection, tests such as tailpipe emissions and vehicle braking are conducted. Inspectors may abruptly apply the brakes or pull the handbrake sharply, which can cause the vehicle's computer to misjudge and trigger the fault light after inspection. Below are the specific details about vehicle annual inspection: Scope: In addition to safety inspections, the annual inspection includes checks on the vehicle's appearance, chassis, lights, horn, and tailpipe emissions to promptly eliminate potential hazards. It also involves reviewing the owner's driving license, vehicle registration, and car insurance. Any outstanding traffic violations must be resolved; otherwise, the vehicle will not pass the inspection. Time: The driving license has a corresponding inspection period, which can be found on the duplicate of the vehicle registration. The inspection must be completed at the vehicle management office.
I encountered a similar situation after my last annual inspection. Later, I found out that the testing station's operations might interfere with the vehicle's sensors. Especially during the emissions test, when the engine runs at high RPM for an extended period, it can cause temporary error data in the oxygen sensor or catalytic converter, triggering the dashboard warning light. Some vehicles may have their battery disconnected, or the OBD port might not be securely plugged in after the test, leading to false alarms. I recommend turning off the engine and waiting for 15 minutes before restarting—many temporary faults will clear automatically. If the light remains on, using a diagnostic tool to read the fault code is the most reliable approach. Don’t rush to repairs; there’s a good chance nothing is actually broken. Such sporadic faults after inspections are quite common and often disappear after a few days of driving. As long as the vehicle runs normally, there’s no need to worry too much.
I've researched this issue, and there are generally three scenarios where the warning light comes on after the annual inspection: the OBD device connection during the inspection line may trigger temporary fault codes; high-speed conditions during the emissions test can cause sensor misjudgments; and there's also the self-check errors caused by the computer reset after the battery is disconnected. In fact, most of the time, there's nothing wrong with the car itself—it's just the electronic systems being interfered with by the inspection process. If the warning light is yellow, you can usually continue driving, but pay attention to any actual symptoms like sluggish acceleration or increased fuel consumption. However, if the engine light is red, you must shut it off immediately. It's best to go to a 4S shop to read the fault codes for confirmation, as they have professional equipment. Nowadays, inspection stations usually remind you about this situation.
After my last vehicle inspection, the engine light came on. The technician said it was normal. The exhaust emission test requires high RPMs, which might cause the sensors to falsely report carbon buildup or excessive emissions. Additionally, many vehicles will perform self-checks on systems like EPB and ABS after a power disconnection, and incomplete initialization can also trigger warnings. Usually, these fault codes are sporadic error codes that can be cleared with a diagnostic tool. If it's inconvenient to visit a repair shop, you can try turning the ignition on and off three times to reset the computer. Note that tire rotation might also trigger the tire pressure monitoring light, which can be reset manually. The key is to distinguish the color of the warning lights.
