Circuit Description

WARNING: This page is about a different car, the 2004 Pontiac Vibe. However, it is still accessible from the selected car via links, so may be relevant.

The DTC P2195 Heated Oxygen Sensor (HO2S) Signal Biased Lean Sensor 1 diagnostic monitors the signal voltage of the HO2S. The heated oxygen sensor (HO2S) produces a voltage that varies between 100-900 mV. The powertrain control module (PCM) monitors this voltage and determines by the exhaust gas oxygen content whether the air/fuel mixture is rich or lean. When the voltage input at the PCM is about 100 mV, the HO2S is indicating a lean air/fuel mixture. When the voltage input is about 900 mV, the HO2S is indicating rich air/fuel mixture. The PCM constantly monitors the HO2S signal during Closed Loop operation and compensates for the rich or the lean condition by decreasing or increasing fuel injector pulse width. A DTC P2195 may set if the HO2S 1 voltage remains excessively low for an extended period of time.

DTC P2195

Air Fuel Mixture	Exhaust O2 Content	HO2S 1 Output	Fuel System Response
Lean Mixture	High Oxygen	Low Voltage	Rich Command
Rich Mixture	Low Oxygen	High Voltage	Lean Command