Faulty oxygen sensor and trouble codes – autos – nigeria type 1 diabetes autoimmune disease

An oxygen sensor (O2 sensor) measures the amount of the oxygen in the exhaust gases, sending the voltage signal to the engine computer (ECM). The ECM uses the signal from the front and the rear oxygen sensors to control the engine operation and to monitor the performance of the catalytic converter, which is a major part of the vehicle’s emission control system. A typical modern car has two or four oxygen sensors in the exhaust: one in front of the catalytic converter(s) and one after.

There are few types of oxygen sensors, but here we will consider a commonly used, the voltage-generating type. As the name implies, a voltage-generating oxygen sensor generates small voltage proportional to the difference in the amount of oxygen inside and outside of the exhaust.

When the air-fuel mixture entering the engine is lean (less fuel and more air), there is more oxygen in the exhaust and the oxygen sensor will generate a very small voltage (0.1-0.2V).


This is because the difference between the amount of oxygen inside the exhaust is small compared to the outside. If the air-fuel mixture becomes rich (more fuel and less air), there is less oxygen in the exhaust, so the oxygen sensor will generate more voltage (around 0.9V). By measuring the oxygen sensor voltage, the engine computer (ECM) knows if the air/fuel mixture is lean or rich. To work properly, an oxygen sensor must be heated to a certain temperature. In the 80-s, an oxygen sensor was heated by the hot exhaust gases. Newer cars use heated oxygen sensors, with an electric heating element inside.

A front oxygen sensor is one of the main fuel injection system components used to determine how much fuel is injected in the engine. A faulty or lazy oxygen sensor is a common reason for poor gas mileage. Your mechanic can check the oxygen sensor with a scan tool.

A front oxygen sensor is installed in the exhaust manifold or in the exhaust down pipe, close to the engine, right before the catalytic converter. It monitors the amount of the oxygen in the exhaust gases and provides the feedback signal to the engine computer whether the air-fuel mixture is lean or rich

When the car is started cold, the front oxygen sensor is not fully warmed up, and the ECM does not use the front O2 sensor signal for fuel trim adjustment. This mode is called open loop. Only when the oxygen sensor is fully warmed up, the fuel injection system goes into closed loop mode.

Some cars have a broadband air/fuel ratio sensor installed instead of a regular oxygen sensor. An air/fuel ratio sensor works differently, but serves the same purpose – to detect whether the air/fuel mixture entering the engine is rich or lean. An air-fuel ratio sensor is more precise and can measure wider range of air/fuel ratio.

Typically, the engine bank that contains cylinder 1 is called Bank 1. A typical in-line 4-cylinder engine has only one bank of four cylinders (Bank 1) and two oxygen sensors, one in front of the catalytic converter (in a technical literature it’s called Front O2 sensor or Sensor 1 and one after it (Rear O2 sensor or Sensor 2 . Therefore, in an in-line 4-cylinder engine, the term Bank 1, Sensor 1 simply refers to the front oxygen sensor. Bank 1, Sensor 2 is the rear oxygen sensor. A V6 or V8 engine has two banks (or two parts of that V , each with three or four cylinders respectively. Usually, in a V6 or V8 engine, the bank that contains the cylinder number 1 is called Bank 1 and the opposite bank is called Bank 2. A typical V6 or V8 engine has two catalytic converters and four oxygen sensors: Sensor 1 or Front O2 sensor refers to a sensor closer to the engine, before the catalytic converter and Sensor 2 or Rear O2 Sensor is the one after. For example, the Bank 1 Sensor 2 is the rear oxygen sensor of the bank containing the cylinder number 1.

Oxygen sensor problems are common. A faulty oxygen sensor may cause poor gas mileage, emission test failure and various driveability problems (hesitation, poor acceleration, surging, etc.). If the oxygen sensor has a problem, the check engine light on the instrument panel will come on. Here are few examples of engine trouble codes that could be cause by a problem with an oxygen sensor: