Operation CHARM: Car repair manuals for everyone.
Manuals through 2025 now available!

Our trusted friends have launched a new website named LEMON, which has newer manuals. It also contains all the CHARM manuals.

LEMON is the spiritual successor to CHARM, I recommend you try it!

Link: lemon-manuals.la or lemon-manuals.org.ua

(Some people have issue connecting. LEMON is investigating. For now, use Firefox or change your DNS server)

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H70 - Monitor HO2S (PID)



- Key On, Engine Running.

- Engine at operating temperature.

- Access suspect HO2S PID using Scan Tool.

NOTE: (HO2S displayed as HO2S on Scan Tool.)

- View HO2S PID while wiggling, bending, and shaking small sections of the EEC harness from the PCM to the HO2S.

- Did the HO2S voltage stay high (greater than 0.45 volts) or low (less than 0.45 volts)?

YES -- ISOLATE cause of lack of HO2S switches and service. Complete PCM reset to clear DTCs. Clearing Diagnostic Trouble Codes

Rerun quick test. Diagnostic Subroutines (DSR) - Extracting Codes

NO -- Go to H71. H71 - Test Drive While Monitoring HO2S PID