The purpose of an Oxygen Sensor
The Oxygen sensor is an electronic device that measures the proportion of oxygen (O2) in the gas or liquid being analyzed located in the exhaust pump. The O2 sensor is mounted in the exhaust manifold to monitor how much unburned oxygen is in the exhaust as the exhaust exits the engine. Monitoring oxygen levels in the exhaust is a way of gauging the fuel mixture. It tells the computer if the fuel mixture is burning rich (less oxygen) or lean (more oxygen). One end of it detects the amount of oxygen while the other end connects to the wiring that relays the sensor's reading to the ECU.
Heated and Non-heated Oxygen Sensors
The oxygen sensor must be hot (about 600 degrees or higher) before it starts to generate a voltage signal, so many oxygen sensors have a small heating element inside to help them reach operating temperature more quickly and will stay at the proper temperature for a more extended period. That's why three and four wire heated oxygen sensors were created, in order to reach operating temperature more rapidly.
Non-heated sensors were used in older cars and were burned by the exhaust gases. But it could take a minute or longer to reach the temperature required for operation.
Narrowband and Wideband Oxygen Sensors
A narrowband O2 (Oxygen) sensor only reads if rich or lean is running the engine, the stoichiometric air/fuel ratio is 14.7:1. A wideband O2 is designed to read a broad range of air-fuel ratios. Some wideband will read from 10:1 up to 20:1. Knowing how far we are away from Stoich, we can calibrate the engine under all conditions. Especially the areas of full power which are critical to performance and longevity.
Upstream and Downstream Sensors
The upstream oxygen sensor is located before the catalytic converter. This measures the level of pollutants coming directly from the engine. It also senses any raw, unburned fuel coming from the combustion chambers. The downstream oxygen sensor is located directly after the catalytic converter. This sensor measures the pollutants making it through the converter and out of the tailpipe. The data from this sensor is compared to that of the upstream sensor. If the data between the two sensors becomes more similar, the vehicle's computer may trigger a catalyst inefficiency check engine code, which turns on the Check Engine light.
It’s always important to know the location of the oxygen sensor if it fails. The number and location of the oxygen sensors are specific to every vehicle's year, make and model. The location of the oxygen sensor is usually identified by position (sensor 1, sensor 2) and by cylinder bank (bank 1, bank 2).
Bank 1 is the side of the engine where cylinder #1 is located.
Bank 2 is opposite to Bank 1.
Sensor 1 is the upstream sensor.
Sensor 2 is the downstream sensor.
If it is a four-cylinder engine, there is only one bank: bank 1.
Over time the oxygen sensor can get worn out because of built up carbon deposits over it, which can cause the faulty function. Or the sensor can also get contaminated with silicon content from the coolant or antifreeze.
If the oxygen sensor fails, there will be some symptoms that will inform you about its failure.
Rough Engine Idle
A bad oxygen sensor will send wrong information to the ECU. This may cause sending more fuel to the engine than required. Then the engine can start to stall. This causes the engine to have a rough idle.
A defective oxygen sensor will fail to keep the exhaust emissions under check, thereby resulting in increased exhaust emissions. Increased emissions are due to the engine running rich/lean.
Poor Gas Mileage
An automobile's gas mileage can be broken because of the worn-out oxygen sensor. The ECU sends a wrong amount of fuel to the engine because of a bad sensor which may result in decreased gas mileage.
When the amount of air-fuel mixture sent to the engine is not optimal, the combustion in the engine cylinders gets affected, which can cause the engine to misfire. This usually occurs either when the engine accelerates or idles. Engine hesitation, which happens during acceleration, is also an indicator of a bad oxygen sensor.
If you clean the oxygen sensors regularly, it will keep them from malfunctioning fast. Unheated 1 or 2 wire O2 sensors on 1976 through early 1990s vehicles can be replaced every 30,000 to 50,000 miles. Heated 3 and 4-wire O2 sensors on the mid-1980s through mid-1990s applications can be changed every 60,000 miles. On OBDII equipped vehicles (1996 & up), a replacement interval of 100,000 miles is recommended.
Direct-Fit or Universal-Fit
Direct-Fit Oxygen Sensor
Direct fit type oxygen sensors are just like in the Original Equipment (OE), as opposed to “Universal” fit sensors, which can be used in multiple applications. Direct Fit sensors are easy to install with No Wire Cutting or Splicing required, with made to measure cable lengths and original connector plugs fitted. Direct Fit Oxygen Sensors are matched to the vehicle application (make, model and series) and cannot be mixed and matched. They are easy to install.
Universal-Fit Oxygen Sensor
Universal oxygen sensors were widely used in the early years of vehicles that were equipped with oxygen sensors. It requires some minor modifications. This style fits hundreds of applications, but you still need to confirm your application before purchasing. This style is recommended only if your vehicle already has a universal-fit oxygen sensor in it. Incorrect use of a universal sensor can result in serious damage to the engine management system, including the failure of the engine control unit (ECU) or the catalytic converter.
Frequently Asked Questions
How many oxygen sensors does my vehicle have?
This depends on your automobile's year, make and model. Older cars had a minimum of two sensors whereas newer automobiles can have six, eight or more oxygen sensors.
What is California emissions sensor?
This sensor is designed specially to meet the emissions specifications for the State of California.
My oxygen sensor has an orange/black/white color. What does it mean?
An orange-colored oxygen sensor is usually an indication of lead poisoning. The oxygen sensor might also turn black indicating carbon buildup or may turn white due to silicone poisoning or antifreeze contamination. The source of these problems should be inspected and fixed, before replacing the oxygen sensors.
What do the P0130 and P0136 codes mean?
The P0130 code indicates the malfunctioning of the oxygen sensor (Bank 1, Sensor 1) and P0136 code indicates a defective oxygen sensor (Bank 2, Sensor 1).