What is the fault when checking the engine emission system?
2 Answers
Checking the engine emission system may reveal faults caused by a dirty three-way catalytic converter or oxygen sensor, which triggers the warning light. In such cases, it is necessary to visit a 4S dealership for resolution. Automobile emission standards refer to regulations on the content of harmful gases such as CO (carbon monoxide), HC+NOx (hydrocarbons and nitrogen oxides), and PM (particulate matter, soot) emitted from vehicle exhaust. The three-way catalytic converter is a device that transforms harmful gases like CO, HC, and NOx from vehicle exhaust into harmless carbon dioxide, water, and nitrogen through oxidation and reduction reactions. The core component of the three-way catalytic converter is a porous ceramic material installed in a specially designed exhaust pipe. It is called a carrier because it does not participate in the catalytic reaction itself but is coated with precious metals such as platinum, rhodium, palladium, and rare earth coatings. It is the most important external purification device installed in the vehicle's exhaust system. The oxygen sensor is an essential component. Since the air-fuel ratio of the mixture significantly affects the purification capability of the three-way catalyst for CO, HC, and NOx, an oxygen sensor is installed in the exhaust pipe to detect the oxygen concentration in the exhaust and send feedback signals to the ECU. The ECU then adjusts the fuel injection amount to maintain the air-fuel ratio near the theoretical value. (Text/Photo/Video: Pacific Auto Network Xu Shuanghe)
When the engine emission system detects a fault, I think it's common but not complicated. First, it could be an oxygen sensor issue—this component monitors the oxygen level in the exhaust. If it ages, it sends incorrect signals to the ECU, leading to improper air-fuel mixture and triggering the warning light. A clogged or burnt catalytic converter can also set off the alarm due to inadequate exhaust purification. Another possibility is a stuck EGR valve, which affects exhaust gas recirculation. I've dealt with similar cases before and recommend scanning the OBD codes immediately—for example, P0420 indicates low catalytic converter efficiency. Don't delay, or fuel consumption may spike, and the vehicle might fail the annual inspection. For routine maintenance, cleaning sensors and inspecting the exhaust system can extend component lifespan.
