Oxygen Sensor Testing

Oxygen Sensors: What Do They Do?

Oxygen sensors are devices which measure the amount of oxygen in the gas or liquid that is being analyzed.

Today, oxygen sensors are being used mainly in cars. They sense the amount of oxygen in the exhaust gas being emitted from the car and determine if the air to fuel ratio is at an optimum. The ideal or optimum air-fuel ratio is said to be 14.7:1.

When the amount of air in the exhaust is greater, then the mixture is said to be a lean mixture. In this case, the exhaust fumes will be full of nitrogen oxides. Such a mixture may often cause an increase in the fuel efficiency of the car, but it may lead to an eventual damage to the engine.

When the amount of fuel in the exhaust is greater, then the mixture is said to be a rich mixture. In this case, the exhaust fumes will be full of unburnt fuel vapors that are full of hydrocarbons. This may cause an increase in the power of the car, and a decrease in the car’s fuel economy. However, this can eventually lead to damage of the catalytic converter of the car.

The engine management computer or ECU checks the data supplied by the oxygen sensor against look-up tables and adjusts the air-fuel ratio in order to have complete combustion occurring in the engine.

Oxygen Sensor Testing: Importance of Oxygen Sensor Testing

From the above, we can see that an oxygen sensor performs an important function in a car: it ensures that the car performs optimally. Along with this function, an oxygen sensor is also useful to maintain emission levels from the car’s exhaust gas in order to control environmental pollution.

Thus it is very clear, that the oxygen sensor of the car must be kept in good working order.

Normally, an oxygen sensor has a life for 30,000 to 50,000 miles in an un-heated condition and for 100,000 miles in a heated condition. Apart from that other factors such as soot on the ceramic element on the sensor, use of leaded fuels, or use of fuels with silicones or silicates can lead to damage and failure of the oxygen sensor and hamper the performance of the car.

Therefore it is extremely essential to know if the oxygen sensor is performing as it should be. The method to test this is known as Oxygen Sensor Testing.

How To Determine If The Oxygen Sensor Is Working Properly?

One can determine if the oxygen sensor is working properly or not if the typical symptoms show up.

One symptom is if the car’s fuel economy drops or if the car begins to lose power.

However, as a disclaimer, it would be right to state here that these symptoms do not necessarily point towards only a failure of the oxygen sensor. But it could be one of the factors or causes. Therefore it would be the best to check it out whilst one is looking into the causes.

Most cars also have a sensor light on the dashboard of the car. However, one should consult the owners’ manual before rushing off to change the sensor when the light comes on. More often than not, the light is triggered when the car has run a certain number of miles or has been started a certain number of times.

Oxygen sensor testing is the method used by most automobile mechanics to see if the oxygen sensor is in working order. To do this, the equipment needed is a high impedance DC voltmeter. One can say that this voltmeter is an Oxygen Sensor Tester.

Attach the positive lead of the voltmeter to the oxygen sensor’s output wire while it is attached to the car’s ECU. One can use jumper wires to gain this access as well. The negative lead of the voltmeter is to be attached to the ground or on the engine block or an accessory bracket.

Set the voltmeter to look for 1 volt DC. In cold, the engine should output between 0.1 volts to 0.2 volts while when the engine has been running for over 20 minutes, it would be warm and the output should fluctuate between 0.1 volts to 0.9 volts.

Some cars use either 2 or 3 wires instead of 1 wire. In these cars, the heated sensors will give an output of 12 volts on one lead, ground on the second lead and the sensor signal on the third lead. In these cars, when you turn the key to ‘ON’ but do not start the engine, there will be a change in the signal.

This is a simple method of testing if the oxygen sensor is working properly or not.

This way, one can ensure that the oxygen sensor in one’s car is in proper working order and if not, one can take the necessary steps to change, replace or repair it.