If the performance of the three-way catalyst fails or is missing, the fault indicator light of the car will usually light up. This is because the emission system of modern cars is equipped with sensors that can monitor the working status of the three-way catalyst and the composition of the exhaust gas. Once the three-way catalyst fails to function properly, the sensor will detect the abnormality and trigger a fault light as a warning.

The three-way catalyst is a core component in the automotive emission system, with a metal tank like appearance and a honeycomb shaped ceramic carrier inside. These carriers are coated with precious metal catalysts that can promote chemical reactions, such as platinum, palladium, and rhodium. The function of these catalysts is to convert harmful gases in exhaust into harmless water, carbon dioxide, and nitrogen, thereby significantly reducing pollution from automobile exhaust.

The fault light is an important component of the car fault diagnosis system, which lights up when any system or component of the vehicle has a problem. For example, when the engine control unit detects an abnormality in the emission system, it may light up the engine malfunction light or a dedicated exhaust emission indicator light to remind the driver to check and repair the vehicle as soon as possible.

Whether the diesel particulate filter (DPF) will sound an alarm without using a three-way catalyst mainly depends on the specific design and operating status of the vehicle.

Independent working mechanism of three-way catalyst and DPF

The three-way catalyst is mainly responsible for treating hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx) in gasoline vehicle exhaust, converting them into harmless carbon dioxide, water, and nitrogen. DPF is a device used in diesel vehicles to filter particulate matter (such as soot) from exhaust gases. The two belong to different emission treatment systems and usually work independently.

The impact of missing three-way catalyst on DPF

Weak direct correlation: Sensors in emission control systems mainly monitor parameters such as exhaust composition and temperature. If only the three-way catalyst (gasoline vehicle) is removed, it usually does not directly affect the sensor or regeneration mechanism of the DPF.

The possibility of indirect impact: If the failure of the three-way catalyst leads to an abnormal increase in exhaust gas temperature or a change in harmful substance concentration (such as an increase in incompletely oxidized carbon particles), it may indirectly affect the filtration efficiency or regeneration process of the DPF, but this situation is more likely to be related to high exhaust gas temperature or regeneration failure.

System design differences: Some vehicle models may use shared sensors (such as oxygen sensors) to monitor exhaust status. If both sensors share the same sensor and the three-way failure causes abnormal signals, it may trigger a DPF alarm.

Common causes of DPF alarm

Excessive accumulation of particulate matter: It is necessary to regularly burn particulate matter at high temperatures or chemically to restore filtration efficiency.

Regeneration failure: If the temperature is insufficient or the time is too long during the regeneration process, an alarm may be triggered.

Sensor malfunction: Malfunctions in the temperature or pressure sensors of the DPF itself may also cause false alarms.

Conclusion: Under normal circumstances, removing only the three-way catalyst will not directly cause DPF alarm. If an alarm occurs, it is recommended to check the status of the DPF itself or whether the system parameters are normal.