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2000 Acura Integra P0420 Code: Universal vs. Direct Fit Catalytic Converter & Oxygen Sensor Diagnosis

Model: 2000 Integra Fault Code: P0420 Posted: 2007-10-09 11:05

I own a 2000 Acura Integra GS with 65,235 miles and an automatic transmission. One morning, I noticed a severe rattling noise when starting the car. The shop diagnosed a failing catalytic converter and replaced it with a universal-fit converter to save costs. Immediately, the rattle stopped. Two days later, the engine check light came on. The shop scanned the vehicle and found P0420 — indicating a catalytic converter efficiency failure. They suggested replacing the upstream oxygen sensor, which I did. After clearing the code, I hoped the issue would be resolved. However, after driving on the freeway, the check engine light returned. I took it back to the shop, and they replaced the converter again with a new one — this time claiming it was defective. The code cleared temporarily, but returned the next day. A second shop confirmed the same P0420 code. I now need to pass emissions testing within three weeks, and am seeking an emissions waiver due to repeated failures. I’m currently considering two options: installing a direct-fit catalytic converter or replacing the rear oxygen sensor. My question is: Does a faulty oxygen sensor trigger a P0420 code? I’ve heard conflicting advice — some say it does, others claim it only occurs when the rear O2 sensor fails to switch signals at a different rate than the front one. Is there a specific diagnostic code for oxygen sensor failure? Are there reliable ways to test these components before replacement? Any guidance on whether a universal-fit converter is safe or effective in this model would be greatly appreciated. I’m looking for accurate, technically sound advice to avoid further costs and ensure compliance with emissions standards.

Related fault codes
P0420
Comments (10)
Anonymous 2007-10-09 12:00

A faulty upstream oxygen sensor does not directly cause a P0420 code. The P0420 sets when the rear oxygen sensor shows the same signal rate as the front, indicating poor catalytic converter efficiency. A bad sensor typically fails by becoming inactive (no switching). In some vehicles, universal-fit converters may not be compatible and could lead to recurring issues. A direct-fit converter is generally recommended for better performance and compatibility.

Anonymous 2007-10-09 13:45

An oxygen sensor will only trigger a P0420 code in rare cases — typically when the front O2 sensor is brand new, the rear sensor is aging, or it's a Chrysler-made component. Even then, this scenario is uncommon. Direct-fit converters are often considered more reliable and properly matched to the vehicle’s system. For best results, use an OEM-quality converter and have other engine systems inspected to determine if underlying issues caused the original converter failure.

Anonymous 2007-10-09 14:13

To me, a 'direct fit' converter typically refers to an OEM-equivalent product like Walker Brand. While this may be considered a high-quality option, it's not universally agreed upon. A good point from COMP — perhaps the converters were functioning correctly and engine-related issues eventually led to their failure.

Anonymous 2007-10-09 16:51

I’ve seen too many poorly installed converter replacements to ignore this issue. In my experience, 'direct fit' should be interpreted as 'universal fit' — these can often be modified with welding and cutting. However, there's no guarantee they’ll match the correct size or function properly. While some may reduce emissions slightly, they don’t perform reliably compared to OEM units. The cost of metals in converters is significant — it’s hard to understand why anyone would expect a $150 converter to perform as well as a $500 one.

Anonymous 2007-10-10 06:53

Many consumers make purchasing decisions based on price rather than long-term value or performance.

Anonymous 2007-10-10 08:41

The issue is not lack of information — it's a lack of proper technician training and awareness of vehicle-specific requirements.

Anonymous 2007-10-10 10:53

I’ve had several customers request the cheapest available option, even after explaining the risks. I’ll install it, but no warranty is implied for such modifications.

Anonymous 2007-10-10 11:08

Thank you all for your input — this has been incredibly helpful. I admit I chose a low-cost converter initially based on price. This experience has taught me a valuable lesson: cost does not always equal reliability or performance.

Anonymous 2007-10-10 11:40

It’s not your fault at all. The technician should have clearly advised you about the risks of using a universal-fit converter in this model, especially given known compatibility issues with older Acura Integras.

Anonymous 2007-10-10 15:46

Assuming he is actually a qualified technician and not just a muffler shop installer — this kind of oversight highlights the need for better technical knowledge and vehicle-specific guidance in repair shops.