Why Your Check Engine Light is On: Understanding P0420 and the Secondary Air Injection System Relay “B” Circuit Malfunction
If you own a car, you may have experienced the annoyance and anxiety of seeing the check engine light on. While some issues are minor and temporary, others can be more serious and costly.
One of the most common trouble codes that trigger the check engine light is P0420, which indicates a problem with the secondary air injection system relay “B” circuit. In this article, we will explain what this code means, what causes it, and what you can do to fix it.
Have you ever been driving peacefully and suddenly notice that your car’s dashboard is illuminated with a bright orange light? This is the check engine light, and it can be a signal that something is wrong with your vehicle. However, the problem may not be obvious, and you may need to take your car to a mechanic or a diagnostic tool to determine the issue.
One of the codes that are frequently associated with the check engine light is P0420, which implies a problem with the secondary air injection system relay “B” circuit. Let’s explore what that means and how to address it.
What is the secondary air injection system?
To understand P0420, we need to know what the secondary air injection system is and what it does. This system is designed to reduce the emissions of harmful pollutants from the exhaust gases of a car’s engine. When the engine is cold, it produces more pollutants, as the catalytic converter needs to reach a certain temperature to work efficiently.
The secondary air injection system injects fresh air into the exhaust stream, which helps to heat up the converter faster and reduce emissions. The system uses an air pump, a set of one-way check valves, and a relay to control the flow of air.
What is the secondary air injection system relay “B” circuit?
The secondary air injection system relay “B” circuit is a specific part of the system that is responsible for controlling the air pump.
The relay is an electrical switch that opens and closes a circuit to allow or block the flow of current. In this case, the relay “B” controls the air pump that injects air into the exhaust system. If the relay or the circuit that connects it to the engine control module (ECM) fails, the air pump may not work as intended, leading to increased emissions and triggering the check engine light.
What causes P0420 and how to diagnose it?
P0420 can have several causes, and diagnosing the exact one can be tricky. Some possible culprits are:
- A faulty secondary air injection system relay “B”
- A damaged or clogged air pump
- A disconnected or corroded relay or pump connector
- A vacuum leak or restriction in the air supply hoses or check valves
- A failed or contaminated catalytic converter
- An issue with the ECM or its sensors
To diagnose P0420, you need to use an OBD-II scanner or a diagnostic tool that can read the trouble codes and the live data from your car’s computer. You should also inspect the secondary air injection system and its components visually, check the wiring and the connectors, and test the relay and the pump. If you are not confident in your skills or tools, it’s best to take your car to a certified mechanic or a dealership.
What can you do to fix P0420?
The best way to fix P0420 depends on the exact cause of the problem. In some cases, you may need to replace the secondary air injection system relay “B” or the air pump, clean or replace the check valves or the air supply hoses, or repair the wiring or the connectors.
In other cases, you may need to replace the catalytic converter or the ECM. The cost of the repair can vary greatly, from a few dollars for a simple fix to hundreds or thousands of dollars for a major replacement.
The secondary air injection system relay “B” circuit malfunction is a common issue that can trigger the check engine light and affect the performance and the emissions of your car. By understanding what this code means, what causes it, and what you can do to fix it, you can save yourself time, money, and stress. Remember to diagnose the exact cause of P0420 before attempting any repair, and seek professional help if needed.
- What happens if you ignore P0420?
Ignoring P0420 can lead to increased emissions, reduced fuel economy, and potential damage to the catalytic converter or other components. You may also fail an emissions test or risk getting a ticket or a fine for driving with a faulty system.
- Can P0420 go away on its own?
P0420 may go away on its own if the issue was temporary or intermittent, but it’s not guaranteed. It’s best to diagnose and fix the problem as soon as possible to avoid further damage or complications.
- Can you drive with P0420?
You can drive with P0420, but you should get it checked as soon as possible to prevent further issues. Driving with a malfunctioning secondary air injection system can affect the performance and the safety of your car.
- How much does it cost to fix P0420?
The cost of fixing P0420 depends on the exact cause of the issue and the type of repair needed. It can range from a few dollars for a simple fix to hundreds or thousands of dollars for a major replacement.
- What else can trigger the check engine light?
The check engine light can be triggered by various issues, such as a malfunctioning oxygen sensor, a loose gas cap, a faulty mass airflow sensor, or a damaged spark plug. It’s important to read the code and diagnose the problem before attempting any repair.