How to Fix the Check Engine Light on a Mini Cooper – P0420 Error Code

by parker
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Welcome back to another episode of The Savage Garage. In today’s video, we will be addressing the check engine light issue on a Mini Cooper. After a few weeks of driving, the engine light came on and the car started to experience reduced fuel economy and a slight decrease in performance. To understand the cause of this issue, we will be using a scan tool to diagnose the problem and find a solution.

Before we begin, I would like to introduce you to the Topton scan tool, which is a versatile device that allows us to read generic codes and analyze live data. If you want a detailed review of this tool, check out our video where we go into depth about its features and functionality.

To get started, we connect the scan tool to the Mini Cooper’s OBD port, which is located under the dashboard. Once connected, we turn on the ignition and perform a generic OBD scan to retrieve any stored fault codes. The scan reveals a P0420 error code, which indicates a catalyst system efficiency below threshold in Bank 1. This code is a common issue in many cars and suggests that the catalytic converter is not functioning properly.

To confirm our diagnosis, we examine the live data from the oxygen sensors. Normally, the first oxygen sensor in Bank 1 should fluctuate between 0.1 and 0.9 volts, while the second sensor after the catalytic converter should maintain a steady voltage around 0.4 or 0.5 volts. However, in our case, both sensors are displaying similar voltage readings, indicating that the catalytic converter is not effectively reducing CO2 emissions.

There are several possible causes for a malfunctioning catalytic converter. One potential reason could be the recent head gasket repair, during which the converter could have been damaged by burning off excess water. However, without further investigation, it is difficult to determine the exact cause. In any case, we will be replacing the catalytic converter that connects to the exhaust manifold.

The catalytic converter we obtained is a high-quality aftermarket product. It comes with two oxygen sensor ports, making it necessary to transfer the sensors from the old catalytic converter to the new one. The replacement process involves removing the coolant reservoir, bending the heat shield, and accessing the bolts that secure the old catalytic converter to the exhaust manifold. With the help of an electric ratchet, we quickly remove all the necessary components.

Once the bolts are removed, the old catalytic converter is free from the engine. The only thing holding it in place is the oxygen sensor wiring, which we can easily disconnect for easy removal. We install the new catalytic converter in reverse order, securing it to the exhaust manifold and reconnecting the oxygen sensors. After reassembling the other components, we start the engine to ensure that the check engine light is no longer illuminated.

In conclusion, a P0420 error code in a Mini Cooper usually points to a faulty catalytic converter. By using a scan tool to identify the issue and replace the defective part, we can resolve the check engine light problem and restore the car’s performance. It is important to remember that this process requires some mechanical skills and knowledge, so if you are not confident in completing it yourself, it is best to consult a professional mechanic.

If you found this article helpful, please share it with others who may be facing a similar issue with their Mini Cooper. As always, let us know in the comments if you have any questions or suggestions for future videos.

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