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

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General Description




The oxygen sensor-1 is installed on the exhaust manifold (precatalyst) and the oxygen sensor-2 is installed on the exhaust pipe (post catalyst). Each sensor detect the concentration of oxygen in the exhaust gases.

ECM (PCM) detects the air-fuel ratio of the mixture supplied to the engine by monitoring the signal (output voltage) from sensor-1.The signal (output voltage) from sensor-2 is used to detect malfunction of the three way catalytic converter.

Each oxygen sensor heater promotes activation of the oxygen sensor.