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Home >> Lexus >> 2003 >> IS 300 Base, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Diagnostic Tests >> DTC P0420: Catalyst System Efficiency Below Threshold (Bank 1) Or P0430: Catalyst System Efficiency Below Threshold (Bank 2) >> Confirmation Test

Confirmation Test

  1. Connect Lexus scan tool to Data Link Connector (DLC) No. 3. See Figure or connect probe of oscilloscope between terminals OX1A, OX1B, OX2A, OX2B and E1 of ECM connectors.
  2. Start engine and warm it up with all accessories switched off until engine coolant temperature is stable.
  3. Race engine at 2,500-3,000 RPM for about 3 minutes.
  4. After confirming waveform of heated oxygen sensor bank 1, 2 sensor 1 (OX1A, OX2A), oscillate around 0.5 volt during feedback to ECM, check waveform of heated oxygen sensor bank 1, 2 sensor 2 (OX1 B, OX2B). If there is a malfunction both waveforms will be almost the same. Even though a malfunction exits, the MIL may not illuminate.
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