Fehlercode P0420 (Katalysator) | VW, Ford, BMW, Opel, Toyota & Co. (2024)

FAQs

What is the most common cause for a P0420 code? ›

What Is the P0420 Code? Can I Still Drive? The P0420 code signals a low catalyst system efficiency. This code suggests that the oxygen levels are below the desired threshold (Bank 1), which most often results from problems with your car's exhaust or fuel systems.

A catalyst monitor uses signals from the downstream O2 sensor to determine catalyst efficiency. It uses signals from the upstream O2 sensor as a reference point. If any or both of these oxygen sensors fail, they can trigger the P0420 code.

Cracking the Code

A common emissions code seen in the field, a P0420 trouble code indicates that the catalytic converter isn't functioning efficiently. To work at peak efficiency, the emissions or feed gases entering the catalytic converter need to be perfectly balanced and not excessively elevated.

Estimated Cost of Repair for a P0420 Code

The average cost of repairing a catalytic converter can range from $1,000 to $2,500. A catalytic converter replacement starts around $2,000, O2 sensor replacement can cost $150 to $500.

P0420 means a catalytic converter problem affecting its efficiency or a problem with the oxygen sensors. So yes, it could be a bad plug which is allowing unburnt fuel to enter the cat and eventually damaging it.

P0420 is a typical error code caused by exhaust leakage. First, examine the exhaust system for evident damage. Welding could be a simple and inexpensive solution. However, if your exhaust is in bad general condition, it will most likely only be a temporary repair.

You need an OBDII reader to tell you which sensor is bad. You may have 2 or 4 sensors, depending upon whether you have a 4 cylinder, V6 or V8. When the 02 sensor goes bad, it will plug up the catalytic converter. So as soon as you know it's an 02 sensor it needs to get replaced.

Unfortunately, cleaning your catalytic converter does not guarantee it'll work effectively afterward. If your converter is defective, cleaning it will not make an impact and any symptoms present before the cleaning process will return. In the end, if nothing works, a replacement is the way to go.

The P0420 code will set when the catalytic converter isn't able to clear all of the unburnt fuel in the exhaust stream. That could be due to an excessively rich fuel mixture, a leaking fuel injector, or a compression/engine timing issue that won't burn the fuel correctly.

Look for the Exhaust Manifold — Follow the exhaust manifold from the engine. Bank 1 Sensor 1 oxygen sensor is typically mounted on the exhaust manifold or very close to it before the catalytic converter. Locate the Catalytic Converter — Find the catalytic converter, and trace the exhaust pipe back towards the engine.

What is the code P0420 on a BMW? ›

It's the catalytic converter. Or could be the oxygen sensor. Test your oxygen sensor. If it's good, you will most likely have to replace the CC.

If you have a bad MAP sensor your vehicle will not run very good. A bad MAP sensor can cause you to use excessive amounts of fuel and unburned fuel being pumped through your catalytic converter can cause it to go bad but typically PO420 is a catalyst inefficiency code.

How long does it take for P0420 to reset? The car's PCM will reset the code after a fixed interval, during which it rechecks all of its sensors. After around 10-20 cycles, the reset may occur automatically. A cycle is a phase in which you turn on and off the ignition.

Does P0420 Clear Itself? Once you've rectified the root cause of the issue, you can go about clearing the code. If you don't have access to an ODB II reader to clear the codes, it should clear itself within a couple of drives.

By the way, cruise control is often the best way to complete a catalyst monitor. Another car needed to be driven in 2nd gear to pass part of a monitor. Accelerate to 50 MPH, then decelerate to less than 6 MPH without touching the brake. Repeat at least 5 times.