A flickering check engine light on a 2016 Honda Odyssey turned out to be an early warning of a failing catalytic converter.

The vehicle owner brought the Odyssey to OOROO Auto in the Tucson Foothills after noticing the check engine light flickering for a few days before it settled into a steady glow. The van was otherwise running well, with no rough idle or loss of power reported.

As with every visit, OOROO’s technicians performed a comprehensive digital vehicle inspection alongside the engine diagnostic. Rather than stopping at the code that triggered the light, the OOROO team looked at the exhaust and emissions system as a whole, along with the rest of the vehicle’s key maintenance points.

Why the Catalytic Converter Matters

The catalytic converter uses precious-metal catalysts to convert harmful exhaust gases into less harmful compounds before they exit the tailpipe. Oxygen sensors positioned before and after the converter monitor how efficiently this conversion is happening.

When a converter starts to break down internally, several things can happen:

• The check engine light illuminates, often flickering at first before staying steady
• Emissions output rises, which can cause a vehicle to fail smog testing
• Fuel efficiency and engine performance can gradually decline
• Post-catalyst oxygen sensor readings become erratic instead of steady
• Left unaddressed, a failing converter can eventually restrict exhaust flow and affect engine performance

What Our Inspection Revealed

OOROO’s technician scanned the Odyssey’s computer and found a P0420 code, indicating a catalyst efficiency problem on bank 1.

• The technician cleared the code and took the vehicle on a test drive to monitor live catalytic converter temperatures and oxygen sensor voltage
• The bank 1 sensor 2 signal should read as a steady line when the converter is working properly, but it was fluctuating
• Bank 1 sensor 2 voltage was reading erratically, confirming the converter itself was the source of the problem rather than a wiring or sensor fault alone
• Given the vehicle’s mileage of about 106,000 miles and the wear pattern observed, OOROO recommended replacing both catalytic converters, with the bank 1 converter as the minimum necessary repair
• All other emissions monitors passed self-testing except the EVAP system, which was noted for the owner’s awareness

Why OOROO Looks Beyond the Check Engine Light

A check engine light rarely points to just one isolated part. OOROO’s inspection also covered routine maintenance items that keep the rest of the vehicle running reliably:

• Engine oil and filter condition
• Cabin air filter condition, which affects interior air quality and HVAC airflow
• AC system performance, tested with a full diagnostic
• General visual inspection of belts, hoses, and other wear items

Checking these systems together, rather than in isolation, is how OOROO catches small issues before they turn into larger repairs.

The Recommended Honda Odyssey Repair

Based on the diagnostic findings, the following work was completed:

• Removed and replaced the rear (primary) catalytic converter on bank 1, including new gasket and mounting hardware
• Performed a full synthetic 0W20 oil and filter change using Valvoline products
• Replaced the cabin air filter with a premium filter
• Completed an AC system diagnostic test

Replacing the converter with new gaskets and studs, rather than reusing worn hardware, helps ensure a proper seal and reduces the chance of a future exhaust leak at the same joint.

Should Both Catalytic Converters Be Replaced at Once?

Not always. OOROO’s technician recommended replacing both converters due to the vehicle’s mileage and overall wear, but the minimum necessary repair, the bank 1 converter showing the failed sensor readings, was the one addressed during this visit. The second converter’s condition was documented so the owner can plan ahead and decide when to address it, based on budget and how the vehicle performs going forward.

Happy Car Club Membership Savings

The vehicle owner was a member of OOROO’s Happy Car Club and received a membership discount on their service. The Happy Car Club is designed to help drivers save on routine maintenance and repairs over time.

Signs Your Honda May Need Catalytic Converter Repair

Schedule a professional inspection if you notice:

• A check engine light that flickers before staying on steady
• Reduced fuel economy without an obvious cause
• A sulfur or rotten-egg smell from the exhaust
• A rattling noise from underneath the vehicle, which can indicate a converter breaking apart internally
• Failed emissions or smog testing
• Sluggish acceleration or a feeling that the engine is working harder than usual

OOROO’s Approach to Catalytic Converter Repair

This visit shows why a check engine light deserves a full diagnostic rather than a quick code clear. A P0420 code can come from several different causes, and confirming the actual failure with live sensor data during a test drive is what separates a guess from an accurate diagnosis.

It also shows the value of looking at the whole vehicle during a single visit. Addressing the converter alongside routine maintenance like the oil change and cabin filter helps keep every system working the way it should.

If your vehicle’s check engine light has started flickering, or you’re due for routine maintenance, bring it to OOROO Auto in the Tucson Foothills. OOROO’s technicians will inspect it, explain exactly what they find, and help you decide what to prioritize.