Mitsubishi P0420 Error Code: How to Fix It

Q: Can I drive with P0420 code on my Mitsubishi?

You can drive short distances with P0420, but it's not recommended long-term. The code indicates your catalytic converter isn't working properly, which affects emissions and fuel economy. In some states, you won't pass emissions testing with this code active.

Q: Will P0420 cause my Mitsubishi to fail inspection?

Yes, P0420 will typically cause your vehicle to fail emissions inspection in most states. The code indicates the catalytic converter isn't meeting EPA efficiency standards, which is required for emissions compliance.

Q: How much does it cost to fix P0420 on a Mitsubishi?

Costs vary widely depending on the root cause. Oxygen sensor replacement ranges from $200-400, while catalytic converter replacement can cost $800-2000 depending on your specific Mitsubishi model and whether you use OEM or aftermarket parts.

Q: Can bad gas cause P0420 in Mitsubishi vehicles?

Poor quality fuel or fuel contamination can contribute to catalytic converter problems over time, but rarely causes immediate P0420 codes. However, using fuel system cleaner or switching to higher quality gasoline may help if the converter is only mildly degraded.

Q: Why does P0420 keep coming back after clearing it?

P0420 returns because the underlying problem hasn't been fixed. The ECU continuously monitors catalytic converter efficiency, and if it detects the converter isn't working properly during two consecutive drive cycles, the code will reset and the check engine light will return.

Abstract

The P0420 error code on Mitsubishi vehicles indicates that the catalytic converter's efficiency has dropped below the required threshold on Bank 1. This means your catalytic converter isn't cleaning exhaust gases as effectively as it should, which can affect fuel economy and emissions compliance.