Circuit Description

The closed loop mixture ratio feedback system provides the best air-fuel mixture ratio for driveability and emission control. The three way catalyst can then better reduce carbon dioxide (CO), hydrocarbons (HC) and nitrogen oxides (NOx) emissions. This system uses Heated Oxygen sensor 1 (HO2S 1), located in the exhaust manifold, to monitor whether the engine operation is rich or lean. The engine control module (ECM) adjusts the injection pulse width according to the sensor voltage signal. This maintains the mixture ratio within the ideal air-fuel mixture range).

The sensor element of the HO2S 1 is composed of an electrode layer, which transports ions. It has a heater in the element. Together with its control electronics, the sensor outputs a clear, continuous signal throughout a wide range. The HO2S 1 heater is integrated in the sensor. The ECM performs duty cycle control of the HO2S 1 corresponding to the engine operating condition to keep the temperature of the element within the specified range.

DTC P1148 indicates a malfunction in the closed loop control feedback system and will only set along with a HO2S 1 DTC.