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P0421

Hello, thank you for writing in. The code P0421 means the exhaust system is detecting an issue with the fumes being to rich. This can happen when the spark plugs are worn and cause the fuel not to burn correctly,...

Hi there. The P0421 error code typically indicates that the catalytic converter (https://www.yourmechanic.com/services/catalytic-converter-replacement) is wearing out and needs to be replaced. However, it could also be sensors that are damaged sending false information. In regards of the wheel bearing, that...

Hello. The codes P0421 (https://www.yourmechanic.com/article/p0421-obd-ii-trouble-code-warm-up-catalyst-efficiency-below-threshold-bank-1-by-andrew-quinn) and P0401 (https://www.yourmechanic.com/article/p0401-obd-ii-trouble-code-exhaust-gas-recirculation-flow-malfunction-by-jay-safford) refer to the oxygen sensor (https://www.yourmechanic.com/services/oxygen-sensor-replacement) and EGR valve (https://www.yourmechanic.com/services/exhaust-gas-recirculation-egr-valve-replacement), respectively. It is possible that an issue with one is causing the fault to be seen by the other, as they will...

Hello. When you get the P0421 code (https://www.yourmechanic.com/article/p0421-obd-ii-trouble-code-warm-up-catalyst-efficiency-below-threshold-bank-1-by-andrew-quinn), it usually means that you have a failing catalytic converter (https://www.yourmechanic.com/services/catalytic-converter-replacement). It is very common for converters to fail on this vehicle over time. Most of the time I use a scan...