P0421: Warm Up Catalyst Efficiency Below Threshold (Bank 1)
Is your scanner showing P0421?
No worries. We'll show you what it means and how to deal with it.
P0421: Warm Up Catalyst Efficiency Below Threshold (Bank 1)
OVERVIEWWhat Does The P0421 Code Mean?
Basically this means that the oxygen sensor downstream of the catalytic converter on bank 1 is detecting that the converter is not working as efficiently as it should be (according to specs). It is part of the vehicle emissions system.
What Are The Symptoms Of The P0421 Code?
You will likely not notice any drivability problems, although there may be symptoms. The code may be more likely to occur after the engine has had numerous cold starts in the past 1-2 days.
What Are The Potential Causes Of The P0421 Code?
A code P0421 may mean that one or more of the following has happened:
- The catalytic converter is no longer functioning properly
- An oxygen sensor is not reading (functioning) properly
- A sparkplug is fouled up
How Can You Fix The P0421 Code?
Measure the voltage at the oxygen sensor on Bank 1 (the rear sensor, or the sensor after the converter). In fact, it would be a good idea to test each oxygen O2 sensor while you’re at it.
One thing to note is that many vehicle manufacturers offer a longer warranty on emissions-related parts. So if you have a newer car but it’s out of it’s bumper-to-bumper warranty, there still may be warranty on this type of problem.
Many manufacturers give a five year, unlimited mileage warranty on these items. It’s worth checking into.
Recommended Parts
Below are some recommended auto parts to help you address the trouble code affecting your vehicle and get it running smoothly again:
Note: During the purchasing process, please check carefully whether the part you want to buy fits your car!
Check This Video For Reference
Reference Sources
P0421 Warm Up Catalyst Efficiency Below Threshold, OBD-Codes.
