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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Oxygen Sensor: Description and Operation







Front heated oxygen sensor (HO2S)
Linear probe




Preheating, front heated oxygen sensor (HO2S)
Resistance approximately 3 (at 20°C)




Rear heated oxygen sensor (HO2S)
Binary probe




Preheating, rear heated oxygen sensor (HO2S)
Resistance approximately 10 (at 20°C)