Cars used to love springing the odd surprise, such as when you were driving along quite happily, only to suddenly find yourself shuddering to a halt as smoke and steam belched out of seemingly all of the vents and orifices at once.
But not any more. Now, a car can tell you pretty much what's ailing it through a warning light and a fault-code reader. Click here to see our test of the best fault-code readers you can buy.
Here, we explain what some of the most common fault codes mean.
P0420
This is a fault code that indicates a catalyst efficiency that's below the required threshold. The catalytic converter is responsible for transforming exhaust gases into harmless substances, so you don't want it to be underperforming. This fault code usually means that your car's emissions system isn't functioning as it should, which will lead to higher levels of pollutants being released from the engine.
Worse still, if you don't address this issue, it could lead to more extensive damage down the line.
What are the symptoms of the P0420 fault code?
The most common symptom of the P0420 fault code is reduced fuel economy. Other symptoms include a decrease in overall engine performance, an illuminated check engine light, and increased emissions of hydrocarbons. Symptoms may also include rough idling, misfires, and stalling when the car is idling for long periods.
What causes a P0420 fault code?
The most common cause is a damaged or faulty oxygen sensor. There are two oxygen sensors in the exhaust that feed information back to the ECU (Engine Control Unit). If one isn’t working correctly, then the ECU won't be able to control the air/fuel mixture properly, so it throws up the P0420 fault code.
Can you drive with a P0420 code?
You can, but it might not be pleasant. However, if you're having other issues with your vehicle, such as a misfire or if the engine keeps stalling, then it's best to get the fault code checked out as soon as possible to avoid any further damage.
How do you fix a P0420 fault code?
Troubleshooting a P0420 fault code requires some technical knowledge. You will need to inspect the oxygen sensor, catalytic converter, and other related parts in order to pinpoint the source of the problem. Once you've identified the issue, you can replace the affected component using the relevant procedure contained in the Haynes manual for your vehicle.
