Catalytic Converter Monitor

2001 Mitsubishi Mirage LS, 4D Sedan, StandardSECTION Catalytic Converter Monitor

This monitor applies to DTCs P0421. Following conditions must be met during the test:

  • Atmospheric temperature is 14°F (-10°C) or more.
  • A/C switch is in OFF position.
  • On A/T, selector lever is in "D" range.

Monitor takes about 20 minutes to complete. To run monitor, use illustration. See Fig 1 . Perform steps as follows:

  1. Remove all test equipment from vehicle and install all components and connectors that were removed or disconnected during testing.
  2. Start engine.
  3. Accelerate to 45 MPH or more.
  4. Travel 300 seconds or more while keeping speed at 45-60 MPH. On M/T, use 5th gear. Brake pedal may be applied during this period if it is not applied more than a few seconds.
  5. Decelerate to 35-40 MPH.
  6. While keeping accelerator pedal opening degree constant, keep speed at 35-40 MPH for 90 seconds or more (during monitor). On M/T, use 4th gear.
  7. Fully close throttle and decelerate for 10 seconds. Brake may be applied during this period. Then, accelerate until speed is 35-40 MPH. Then repeat steps  6 and  7 five more times.
  8. Return vehicle to shop and turn ignition off.

Fig 1: Running Catalytic Converter Monitor
G99F52600Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
RENDER: 1.0x

NO RELATED

Recommended Tools & Savings

Use the Manual With the Right Hardware

Pair factory procedures with proven DIY tools so the instructions are easier to execute.

Affiliate disclosure: We may earn a commission at no extra cost to you.

When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • You smell fuel, burning insulation, or see smoke.
  • Brakes feel soft, pull hard to one side, or make grinding noises.
  • The engine overheats, stalls repeatedly, or misfires under load.
  • You are missing required tools, torque specs, or safe lifting equipment.
  • You are not confident in the next step or safety outcome.