What are the reasons for OBD failure?
2 Answers
OBD failure can be attributed to the following reasons: 1. Outdated OBD system; 2. Malfunctioning sensors in the OBD system; 3. Engine failure. OBD is a diagnostic system developed for vehicle fault detection. During vehicle operation, the OBD continuously monitors the vehicle's condition with the assistance of numerous sensors. If a fault occurs during operation, the OBD stores it in the form of a fault code. When the vehicle requires maintenance, simply connecting a diagnostic tool can identify the fault location, facilitating repairs by technicians. By reading vehicle data and checking for engine faults or fault codes, an OBD that fails inspection will not pass the annual inspection.
I recently failed the OBD inspection for several reasons. For example, the oxygen sensor was faulty—it monitors emissions and throws errors if aged or water-damaged. There was also a clogged catalytic converter; it triggers a warning light when the engine burns incompletely, causing excessive exhaust emissions. Loose wiring connections are common too—my car had signal interruptions due to corroded plugs. Software issues can arise as well, sometimes due to poor compatibility after ECU updates. The most annoying part was the multiple engine fault codes, often caused by carbon buildup or poor fuel quality triggering chain reactions. Using higher-quality gasoline and regular sensor checks can help prevent issues, but failing OBD inspections affects annual checks and environmental compliance. I recommend first using a diagnostic tool to read the codes yourself to confirm the problem before heading to a professional repair shop—it saves time and hassle.
