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Home >> Lexus >> 2003 >> SC 430 >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Diagnostic Tests >> DTC P0420: Catalyst System Efficiency Below Threshold (Bank 1) Or DTC P0430: Catalyst System Efficiency Below Threshold (Bank 2) >> Confirmation Engine Racing Pattern

Confirmation Engine Racing Pattern

  1. Connect hand-held tester to DLC3, or connect probe of oscilloscope between terminals OXL1, OXL2, OXR1, OXR2 and E1 of ECM connectors. Start engine and warm it up with all the accessories off until engine coolant temperature is stable.
  2. Race engine at 2500-3000 RPM for about 3 minutes. After confirming that waveforms of heated oxygen sensor (bank 1, 2 sensor 1 (OXL1, OXR1 )), waveforms around 0.5 volts during feedback to ECM, check waveform of heated oxygen sensor (bank 1, 2 sensor 2 (OXL2, OXR2)). See Fig 1.
  3. If there is a malfunction in the system, the waveform of heated oxygen sensor (bank 1, 2 sensor 2 (OXL2, OXR2)) is almost the same as that of heated oxygen sensor (bank 1, 2 sensor 1 (OXL1, OXR1)) on the left. See Fig 2. There are some cases where, even though a malfunction exists, MIL may light up or not light up.
    Fig 1: Confirmation Engine Racing Pattern
    G00232361Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    Fig 2: Heated Oxygen Sensor Waveform
    G00232362Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002