P0420 Which Catalytic Converter
P0420 Which Catalytic Converter
Understanding which catalytic converter P0420 points to, how to locate it on your specific engine, and what to do before replacing it.
Bank 1 catalytic converter location for P0420 replacement
Replace with your featured image in WordPress
P0420: Which Catalytic Converter Does It Refer To?
P0420 specifically refers to the catalytic converter on Bank 1 of your engine. Bank 1 is always the side of the engine that contains cylinder number one. On a four-cylinder engine, there is only one bank and therefore only one catalytic converter, so P0420 refers to that single converter. On V6 and V8 engines, the cylinders are split across two banks, and each bank typically has its own catalytic converter. Bank 1 is the side with cylinder one, and its converter is what P0420 is flagging. The Bank 2 converter is covered by a separate code, P0430. If you are only seeing P0420 and not P0430, you only need to address the Bank 1 converter, not both.
🔧 Diagnose Before You Buy a Converter
- 👉 OBD2 Scanner with Live Data (Confirm Which Component Is Failing)
- 👉 Fuel System Cleaner (Try This First)
- 👉 Replacement Downstream O2 Sensor (Rule This Out First)
- 👉 Catalytic Converter Replacement (Bank 1)
💡 Replacing the wrong component is expensive and frustrating. Use a scanner with live data to confirm the converter is actually the problem before purchasing one.
Which Converter by Engine Type
Four-Cylinder Engines (One Converter)
Four-cylinder engines have a single exhaust bank and a single catalytic converter. P0420 on a four-cylinder always refers to that one converter. There is no Bank 2 on these engines. Common four-cylinder vehicles include the Toyota Camry and Corolla, Honda Civic and Accord, Chevy Malibu, Ford Focus, and most compact and mid-size sedans.
V6 Engines (Usually Two Converters)
Most V6 engines have two separate exhaust banks and two catalytic converters, one for each bank. P0420 refers specifically to the Bank 1 converter, which is on the side of the engine containing cylinder number one. The location of cylinder one varies by manufacturer and model, so if you are unsure which side Bank 1 is on for your specific vehicle, a quick search for your make, model, and year will confirm it. Common V6 vehicles include the Toyota Camry V6, Honda Accord V6, Chevy Traverse, and Dodge Charger V6.
V8 Engines (Two Converters)
V8 engines also typically have two exhaust banks and two catalytic converters. P0420 refers to the Bank 1 converter only. On most GM V8 engines like those found in the Silverado and Tahoe, Bank 1 is the driver’s side. On Ford V8 engines, Bank 1 is typically the passenger side. Confirm for your specific vehicle before ordering parts.
What If You Have Both P0420 and P0430?
If both codes are present simultaneously, both converters are flagged. However, having both codes at the same time often indicates a shared root cause like an exhaust leak, a fuel system issue, or a bad MAF sensor rather than two independently failing converters. Always investigate and rule out the cheaper causes before replacing both converters at once.
OEM vs Aftermarket: Which Converter to Buy
Made by or for the original manufacturer. Most expensive option but typically the highest quality and longest lasting. Usually the safest choice for passing emissions long term.
✅ Best long-term choice
Made to bolt directly onto your vehicle’s existing exhaust system without modification. More affordable than OEM. Quality varies by brand. Look for reputable brands with a warranty.
✅ Good value option
Requires cutting and welding to fit your exhaust. The cheapest option but installation is more complex and emission compliance is harder to verify. Not recommended for most drivers.
⚠️ Professional install required
Required in California and states that follow California emissions standards. Must display a CARB executive order number. Using a non-CARB converter in these states is illegal and will fail inspection.
🚨 Required in CA and select states
Before You Buy a Converter: Rule Out These First
Connect an OBD2 scanner with live data capability and watch both oxygen sensors on Bank 1. If the downstream sensor mimics the upstream sensor exactly, the converter is likely failing. If the downstream sensor is stuck at a fixed voltage or barely responsive, the sensor itself may be bad.
A bottle of fuel system cleaner through a full tank costs almost nothing and clears P0420 in borderline converter efficiency cases. Always worth doing before any parts purchase.
The downstream O2 sensor triggers P0420 and a failing sensor produces the same code as a failing converter. At $50 to $150 for the part versus $500 to $2,000 for a converter, ruling out the sensor first is always the right financial decision.
An exhaust leak before the Bank 1 converter corrupts the O2 sensor readings and can trigger P0420 without any converter failure. Have the exhaust system inspected on a lift before purchasing a converter.
Once you have confirmed the converter is the issue, purchase a quality replacement catalytic converter designed for your specific vehicle. Confirm CARB compliance for your state. Have all underlying engine issues resolved before installation and clear the P0420 code with your scanner after the repair is complete.
The Bottom Line
P0420 refers specifically to the Bank 1 catalytic converter, which is always the side of your engine containing cylinder number one. On a four-cylinder, that is your only converter. On a V6 or V8, it is the converter on the Bank 1 side only. Before purchasing any converter, confirm the diagnosis with an OBD2 scanner, try a fuel system cleaner, and rule out the downstream O2 sensor. A replacement catalytic converter is the right fix when everything else has been eliminated, but it should always be the last step in the process, not the first.