1) Connect LEXUS hand-held tester to DLC3, or connect probe of oscilloscope between terminals OXL1, OXL2, OXR1, OXR2 and E1 of ECM.
(2) Start engine and warm it up with all accessories switched OFF until water temperature is stable.
(3) Race engine at 2,500 3,000 rpm for about 3 minutes.
(4) After confirming that waveforms of heated oxygen sensors bank 1, 2 sensor 1 (OXL1, OXR2), oscillate around 0.5 V during feedback to ECM, check waveform of heated oxygen sensors bank 1, 2 sensor 2 (OXL2, OXR2).
HINT: If there is a malfunction in system, waveform of heated oxygen sensors bank 1, 2 sensor 2 (OXL2, OXR2) is almost same as that of heated oxygen sensors bank 1, 2 sensor 1 (OXL1, OXR1) as shown.
There are some cases where, even though a malfunction exists, MIL may either light up or not light up.