What Do I Need To Know About My Oxygen Sensor?

How Many EFIEs Do I Need?

This question comes up a lot. There are literally thousands of models of car, and each has it's own design. The number of oxygen sensors can vary from one to four or more. Do all of them need EFIEs to operate properly with fuel saving devices?

The short answer is, that all oxygen sensors on the engine side of the catalytic converter need EFIE devices. It is rare that there are more than 2 of these. Eight cylinder engines tend to have 2 sensors, one on each exhaust manifold, but often have only one. Six and four cylinder engines tend to have 1 sensor, but can have more. Regardless, all of these upstream sensors must be treated.

The sensors after the catalytic converter, or attached to it, were originally designed to tell the engine computer when the catalytic converter has gone bad, but were generally not used to modify the calculations on how much gas to give to the engine. They left this job to the upstream sensors. However, we are finding many vehicles that ARE using the downstream sensors as part of the air/fuel calculations, and EFIEs are needed on them to get those vehicles to respond. In some cases the vehicle's documentation reports this use of the downstream sensors, but in many cases there is no mention, even though treating the downstreams sensors has solved numerous fuel saving projects. We are now manufacturing a Quad EFIE that will have upstream and 2 downstream EFIE circuits in them to make treating all sensors more economical. We are trying to produce the quad EFIEs economically enough that folks can afford to treat all of their sensors and not have to worry about it.

What Type Of Sensor Do I Have?

This is an important question to answer. There are a number of different types of sensor, and some are handled differently. Oxygen sensors for many years were of a single type. These were more specifically called narrow band oxygen sensors, and almost all EFIEs are designed to work with these. In recent years, a new type of sensor has come out, the wide band oxygen sensor, and these devices communicate with the vehicle's computer in an entirely different way.

However in recent years we have a new type of sensor, known as a wide band sensor. You can find out more about this type of sensor in Oxygen Sensors, Types of. One type of oxygen sensor uses 4 wires. These are usually found on Toyotas, but I expect to see these used more on other vehicles too.

How do you know if you have an AFR sensor or narrow band oxygen sensor? You might get lucky and have it written on the vehicle information tag on your hood. Open the hood and look up. It may be written there. Otherwise, you will need some documentation for your vehicle. I don't mean the owner's guide that is given to you when you buy your new car. If you're going to be installing modifications to your engine, you should have a Haynes or a Chilton's manual for your car or truck, preferably Haynes as these are generally more informative. Another alternative is to get your wiring schematics from www.ahdol.com. This company will give you all of the wiring schematics for your vehicle in .pdf (Adobe Acrobat) format for $12 (last I checked). If you have an AFR sensor, it will be called such in the diagram. Otherwise it will be called, "Oxygen Sensor" or "Heated Oxygen Sensor" or sometimes HEGO (Heated Exhaust Gas Oxygen) sensor. I have found another resource where you possibly can get all of this information for free at AutoZone's web site. You can find out about it here. If you can wait a day or two, we will look your vehicle up for you and tell you what type, and how many sensors you have. Just fill out a Sensor Information Request Form, which gives us the data we need to look up your specific vehicle.

The most easily identifiable form of wide band sensor is the one that has 5 wires. As you might guess, these devices use 5 wires, and sometimes 6 wires, but the 6 wire version is the same sensor with an extra ground wire. You can always know that these are wide band sensors. There are no 5 or 6 wire narrow band sensors.

If you read the Installation Instructions, you'll see there's another reason to have a good wiring diagram for your car. That is so you can find the wires for your sensor(s) up near the computer, where you can easily access them. Believe me, they are worth the money for that alone. But if you have any doubt about the type of sensor you have, they are doubly valuable.

You can test your wires to see what kind of sensors you have. Use the Installation Instructions and read through section "1. Locate the oxygen sensor signal wire". This will describe how to determine which wires have which function from your oxygen sensor. If you have a narrow band sensor, you will find a signal wire that behaves as described in the instructions. If you have an AFR sensor, you will get different electrical phenomena entirely.

Summary

I hope this page hasn't confused you. But it's best to start digging in and finding out what you really have under the hood, so you don't end up purchasing an EFIE that you don't need or can't use. If you still have questions or are unable to find the information on your sensors, fill out the Sensor Request Form, and submit it. We will get back to you with the number and type of oxygen sensors you have, and give you a recommendation on which EFIE you need.