Fix your Catalytic Converter for $10?

Main ideas / concepts / lessons

• The video covers a common diagnostic scenario: an older car throws a P0420 / P420-style code (referred to by the creator as “P420”).
  • This typically indicates low catalytic converter efficiency, as detected by the downstream O2 sensor on Bank 1.
• The creator explains that many different issues can trigger the code, and they focus on determining whether the catalytic converter is actually the problem.
• Instead of immediately replacing the catalytic converter (often expensive and difficult to access), they try:
  • Catalytic cleaner first
  • then an approach involving O2 sensor “spacer” tricks to temporarily prevent the check-engine/emissions warning.

Diagnostic reasoning shown

• They use an OBD-II scanner to read the code.
• They explain the roles of the two O2 sensors:
  • Upstream O2 sensor: monitors whether the engine is running rich or lean; it does not directly measure catalytic converter efficiency.
  • Downstream O2 sensor: monitors catalyst performance by checking oxygen levels after the catalyst.
• They argue that P0420-style codes usually reflect catalyst inefficiency, but they emphasize other causes exist and that they “rule out” alternatives—leaving a dirty catalytic converter as the likely issue.
• To assess catalyst condition, they check tailpipe soot:
  • The Lexus tailpipe is described as pitch black and “thick,” suggesting heavy buildup/soot.

What they recommend (and what they warn against)

Catalytic converter replacement

• Conceptually, the catalyst “should” be replaced.
• However, the creator avoids it due to:
  • cost
  • labor/access difficulty for certain vehicles.

Catalytic cleaner

• They recommend trying Cataclean (about $30, available at O’Reilly’s).
• Key claim: it worked in their case.

O2 sensor spacers / altering sensor readings (warned against)

• They demonstrate a method intended to prevent the ECU from seeing true downstream readings reliably—so the light doesn’t trigger/continue.
• They explicitly warn:
  • “O2 spacers are illegal.”
  • The video is not advice for wrongdoing.
• They frame it as a “just don’t do it” approach and joke about “emissions police” showing up.

Method / instructions presented

A) Catalytic cleaner attempt (Cataclean)

• Choose a catalytic cleaner product:
  • The creator selects Cataclean, citing good reviews and availability at O’Reilly’s.
• Important note they stress:
  • “Read the instructions!”
• Procedure they used (explicitly called out as not standard):
  • Add the cleaner with a full tank of fuel.
• Reported outcome:
  • After about 100 miles, the check engine light turned off.
• Counterexample:
  • Their friend Joe (“the Cheapskate”) reportedly saw the light return after ~100 miles, and planned to use the cleaner periodically.

B) If the light comes on before an emissions test: downstream O2 “spacer” method (warned against)

This section describes a workaround meant to reduce (not fully eliminate) the downstream sensor’s ability to read exhaust gases normally, so the ECU doesn’t set/keep the code.

1) Understand sensor logic before intervening

• Don’t disconnect the downstream O2 sensor:
  • Disconnecting/cutting it would trigger another code and turn on the check engine light.
• The goal is to interfere only with exhaust flow to the sensor, reducing readings.

2) Lift/support the vehicle and pre-soak sensors

• Jack up the car:
  • They lift both sides at once to save time.
• For several days beforehand:
  • Soak the downstream O2 sensors with penetration spray multiple times.

3) Access the downstream O2 sensor (Lexus vs. other cars)

• Lexus-specific issues:
  • Heat shield is bent; they bend it back.
  • Passenger-side sensor wire routing has limited slack.
• Tools mentioned in the narrative:
  • “iPhone screen replacement” tool (used as a bending tool)
  • sockets, wobble extensions, impact wrench
• Their approach for the passenger side:
  • Because slack is limited, they often can’t disconnect the wire easily.
  • They free the sensor enough to remove it.

4) Remove downstream sensor(s)

• Driver side
  • The wire is attached to the frame.
  • Remove fasteners to gain at least ~12 inches of slack for multiple turns needed to remove the sensor.
  • Wire routing involves paths through/near the floor and under/near the driver seat.
• Passenger side
  • Connector is near the console.
  • Disconnect the connector, push wiring through the floor.
  • Use an impact wrench to break the sensor free, then remove it.

5) Build/install “spacers” using non-fouler adapters (workaround)

• They claim:
  • “O2 spacers are illegal”
  • they can’t be purchased from major retailers.
• Workaround described:
  • Buy spark plug non-foulers (about $10).
  • Modify them by drilling out the end to create an O2 spacer-like adapter.
• Additional claims made:
  • “Walmart sells O2 spacers” (and they describe drilling a non-fouler with careful technique).
• Fitment procedure:
  • Screw the modified spacer into the exhaust bung, tighten.
  • Install the O2 sensor by twisting in the correct order so threads seat properly (they describe needing about 5 turns to untwist/align).
• Clearance problem and fix:
  • Sometimes the spacer positions the sensor too close to the frame for a socket to fit.
  • Fix: tighten in stages
    • tighten spacer on sensor first,
    • then tighten spacer to bung using an adjustable wrench.
• Reinstall both sensors:
  • Driver side: reattach wiring.
  • Passenger side: fish wire up through the floor, under dash, reconnect connector.
  • Re-tuck carpet/restore coverings.

6) After installation: results and legal follow-up (as stated)

• Results reported:
  • “A few thousand miles” later: no light, no codes; the car passed inspection.
• Legal follow-up they state:
  • Because spacers are illegal, they removed them immediately and disposed of them properly.
• Their reverse-engineering instruction:
  • “Play everything backwards” to understand removal.
• Disclaimer:
  • The video is “for entertainment purposes only.”

Speakers / sources featured (as stated or implied)

• Mike (“the Backyard Mechanic”) — main narrator/creator
• Daughter — mentioned as informing him the check engine light turned off
• Joe the Cheapskate — referenced friend with different results
• “Emissions police” — used as a humorous/fictional threat
• OBD-II scanner / ECU (engine computer) — systems used for reading/understanding codes
• Retailers/brands mentioned:
  • O’Reilly’s — availability of Cataclean
  • Walmart — mentioned in connection with O2 spacer availability/claims
  • Autozone / Advance Auto Parts / Amazon — claimed not to sell “O2 spacers”
  • Cataclean — product used for cleaning