Check HO2S

IG "OFF". Disconnect HO2S connector.
Check that the HO2S is securely installed.
Check the HO2S for contamination or damage, water intrusion in connector, incorrect fuel pressure, VAC leaks.
Is the sensor normal?
YES
- Go to "Check The Signal Waveform Of HO2S " as below.
NO
- Substitute with a known - good HO2S and check for proper operation. If the problem is corrected, go to "VERIFICATION OF VEHICLE REPAIR " procedure.