Basic Types of Oxygen Sensor
There are 2 basic kinds of oxygen sensor. They are called "Narrowband" and the more modern, and superior, "Wideband" oxygen sensor. These are discussed in more detail in our Knowledge Base articles: Oxygen Sensors Types, and a more specific article on Wideband Oxygen Sensors. The most important distinction is which of these 2 types of oxygen sensors you have. An EFIE made for one type will not work correctly on the other, despite the occasional claim by an ill-informed manufacturer or supplier.
It is often easy to figure out what type of sensors you have. Is your car pre-1997? Then it's Narrowband. Is it an American Car? We've now seen a few Wideband sensors equipped in 2009+ American cars, but none before that. If it is a German or Japanese make and was built after 2000, then you should suspect that it has Wideband sensors. Actually, a very few manufacturers started using Wideband sensors in 1997, but it is only after 2000 that they are used with any regularity. But, here's another test: Does the sensor have more than 4 wires? If it does, then its a Wideband sensor for sure. Note that Toyota and Honda use a 4-wire Wideband oxygen sensor, so this test won't work for those makes. All other manufacturers that equip Wideband sensors use 5-wire or 6-wire Wideband sensors.
Try this: Open your hood. Now look up. Do you see a sticker under the hood with technical data about your vehicle? Often if you have Wideband sensors, they are noted on these stickers for the mechanics. Note that it may be called an AFR (Air/Fuel Ratio) sensor, or AFS (Air/Fuel Sensor). These are all synonyms for a Wideband oxygen sensor.
If All Else Fails
If you still don't know for sure what type of sensors you have, you'll have to figure it out by looking at the actual sensors, and perhaps measuring their voltage. First lets cover some basic facts about oxygen sensors:
- There are only 2 kinds of sensors. Narrowband or Wideband.
- There are 2 basic locations and uses for oxygen sensors. Upstream of the catalytic converter and downstream of the catalytic converter. Sometimes the downstream sensors are mounted in the cat, rather than after the cat.
- When Wideband sensors are used, they are only used upstream of the catalytic converter. Narrowband sensors are used downstream. There is no reason not to use Wideband downstream sensors, but we have never seen this done by any manufacturer as of May 2013.
- V-type engines (V6, V8 etc) with 2 banks of cylinders usually have sensors on each side of the engine. This will mean that there will be 2 upstream sensors, and often 2 downstream sensors also.
- All oxygen sensors are mounted in the exhaust stream of the engine. This will be the exhaust manifold, pipe, catalytic converter etc.
- Downstream sensors were required by law in the U.S. in 1996. Prior to '96 you will sometimes see downstream sensors, but most often you will not. Most of the time, pre-96 engines will have only one Narrowband oxygen sensor. After 1996 you will always see at least one downstream sensor in U.S. cars and trucks. In most cases, cars in the rest of the world also started using downstream sensors at the same time.
Putting It All Together
Look at your engine. How many banks of cylinders do you have? If you have a V6 or V8, there will be 2 banks. 4 cylinder engines or straight 6 engines only have one. Next look at your exhaust pipe and find the upstream sensor(s). How many wires does it have? If it has more than 4, it's Wideband. If it has 4 or less, it's Narrowband... unless it's Toyota or Honda. For these manufacturers, you'll need to measure the voltage to confirm which type it is (see below). Now, count your downstream sensors. We know already that these are Narrowband.
You have now determined what type of sensors you have, and can now select the correct EFIE for your engine. As far as I know, we're the only company that makes EFIEs that will cover all the different variations with one device. We have Quad and Dual Digital EFIEs for the Narrowband types, and Quad and Dual Wideband EFIEs for the Wideband type. Our Wideband EFIEs have both Wideband EFIEs for upstream sensors and Narrowband EFIEs for the downstream sensors. Our Dual Wideband is for 4 cylinder engines and has one Wideband and one Narrowband EFIE, and the Quad Wideband has 2 of each type. You can find our full line of EFIEs in our store, here.
Measuring the Voltage
You probably have been able to identify your sensors without having to measure the voltage. However, if you have a Toyota or Honda with 4-wire upstream sensors, then you will need to measure the voltage of the signal wire. If you look at the wires on the sensor, you will find 2 that are the same color. These will be the heater. Then you will have 2 that are unique. These are the signal and reference wires. These are the only 2 you need to measure. The trick is that you need to measure them while they are in use in a running engine. Test with the engine idling. The easiest way to do this to use a sharp meter probe to puncture the insulation of the wire with your red probe. The black probe should be grounded. Now, if the voltage is above 2 volts, then it's Wideband. If it's below 1 volt then it's Narrowband. Both wires will be above 2 volts for Wideband sensors. For Narrowband one will be between 0 and 1 volt and constantly changing, and the other will be 0 volts.