Toyota 4Runner Catalytic Converter Replacement Guide (1999-2004)

Is Your 4Runner's Catalytic Converter Failing?

The most common sign of a failing catalytic converter in a 1999-2004 Toyota 4Runner is the Check Engine Light turning on. If you scan the code, you will likely see P0420 (Catalyst System Efficiency Below Threshold Bank 1). On V6 or V8 models, you might also see P0430 for Bank 2. This code means the oxygen sensors are detecting that the converter is no longer cleaning the exhaust effectively.

Other symptoms include:

• Poor Engine Performance: You might notice your 4Runner feels sluggish or can't accelerate properly, especially on the highway. This can happen if the inside of the converter breaks apart and creates a blockage.
• Rotten Egg Smell: A strong sulfur or rotten egg smell from the exhaust is a classic sign of a converter that isn't working right.
• Rattling Noises: If the ceramic honeycomb inside the converter breaks, you may hear a rattling sound from under the vehicle.
• Failed Emissions Test: Your vehicle will not pass a smog check with a bad catalytic converter.

OEM vs. Aftermarket Converters for the 4Runner

When it's time to replace the converter, you have two main choices: original equipment (OEM) from Toyota or an aftermarket part. For the 4Runner, this is a big decision.

• OEM Toyota Converters: These are the highest quality and are guaranteed to work with your 4Runner's sensitive computer system. However, they are extremely expensive, often costing over $1,300 for a single part.
• Aftermarket Converters: These are much more affordable. The challenge is that many cheaper aftermarket converters don't have enough of the precious metals needed to satisfy the 4Runner's computer. This can cause the dreaded P0420 code to come back even after you've installed a new part.

Choosing the Right Aftermarket Brand

Not all aftermarket brands are created equal. For a 1999-2004 4Runner, it's often best to invest in a higher-quality aftermarket part to avoid problems.

Tier 1: High-Quality Aftermarket (Recommended)

• MagnaFlow: A well-regarded brand that offers direct-fit and CARB-compliant options. They generally have a good reputation for build quality and are more likely to keep the check engine light off, though they are one of the more expensive aftermarket choices.
• Walker (CARB-Compliant Models): Walker's CalCat line is designed to meet stricter emissions standards and is a solid choice. Their standard federal converters are a budget option, but may be less effective.

Tier 2: Standard/Economy Aftermarket

• AP Exhaust, Eastern Catalytic, Evan Fischer: These brands provide affordable, direct-fit solutions that meet federal EPA standards. They can be a good value, but be aware that on a sensitive vehicle like the 4Runner, there is a higher risk of the P0420 code returning compared to a premium or OEM part.
• Davico Converters: Often the most budget-friendly option, but some owners and mechanics have reported issues with fitment and quality control. This is a 'get what you pay for' option.

Generation Differences (1999-2004)

This year range covers two different 4Runner generations with different exhaust setups.

• 1999-2002 (3rd Gen): These models with the 3.4L V6 or 2.7L 4-Cyl often have a simpler system. Federal emissions vehicles may have one or two converters, while California emissions models have a two-converter setup.
• 2003-2004 (4th Gen): These models with the 4.0L V6 or 4.7L V8 have a more complex system, often with four catalytic converters—two integrated with the exhaust manifolds and two further downstream. A P0420 or P0430 code usually points to one of the main converters, not the manifold converters.
🎬 See this walkthrough for replacing a 4th Gen manifold converter.

Frequently Asked Questions