* Faulty oxygen sensor
* Faulty catalytic converter
* Faulty EGR valve
* Vacuum leak
* Faulty EVAP system
Diagnostic Steps
1. Check the oxygen sensor. The oxygen sensor is located in the exhaust manifold. It monitors the amount of oxygen in the exhaust gas and sends a signal to the engine control unit (ECU). If the oxygen sensor is faulty, it can cause the P0402 code to set.
2. Check the catalytic converter. The catalytic converter is located in the exhaust system. It converts harmful pollutants in the exhaust gas into less harmful compounds. If the catalytic converter is faulty, it can cause the P0402 code to set.
3. Check the EGR valve. The EGR valve is located on the intake manifold. It recirculates a small amount of exhaust gas back into the engine. This helps to reduce emissions. If the EGR valve is faulty, it can cause the P0402 code to set.
4. Check for a vacuum leak. A vacuum leak can cause the P0402 code to set.
5. Check the EVAP system. The EVAP system is designed to prevent fuel vapor from escaping into the atmosphere. If the EVAP system is faulty, it can cause the P0402 code to set.
Repairs
The repairs for the P0402 code will depend on the cause of the code. If the oxygen sensor is faulty, it will need to be replaced. If the catalytic converter is faulty, it will need to be replaced. If the EGR valve is faulty, it will need to be replaced. If there is a vacuum leak, it will need to be repaired. If the EVAP system is faulty, it will need to be repaired.
