Visual Check

Turn the ignition switch "OFF" & Disconnect HO2S (S1) connector.
Check that HO2S (S1) is contaminated or damaged by foreign materials.
Has a problem been found?
YES
- Go to "Check HO2S (S1) performance ".
NO
- Replace the HO2S (S1) with an usable one and check for proper operation. If the problem is corrected, replace the HO2S (S1) and then go to "Verification of Vehicle Repair ".