• What Is An EFIE?


• Which EFIE Do I Need?


• Finding The Signal Wire

EFIE stands for Electronic Fuel Injection Enhancer. The purpose of the EFIE is not to provide fuel efficiency, but to make it possible for a fuel efficiency device to work. The EFIE is designed to manage the Oxygen Sensor readings to the ECU (Environmental Control Unit). Basically, what happens when you install a fuel efficiency device, is that the emissions computer thinks something is wrong. There's nothing wrong, however; the added HHO to the engine will read as more output through the emissions sensors (in this case, the oxygen sensors). The ECU will then make fuel injectors adjust to what the engine now believes is a "lean" air/fuel ratio. It's only trying to adjust for this "wrongness". Without the EFIE, the actions the ECU takes is based on the oxygen sensor data, negating the efficiency increase that would have been realized by the efficiency device.

One fundamental point about an EFIE is that it is not a fuel efficiency device, on it's own. If all you did was add an EFIE to your car, with no other fuel efficiency system, you really won't see any difference in fuel economy. What happens , now, is you are just fooling the vehicle's computer and making it run off-spec, or differently than it was designed for. The EFIE was designed to make the car run according to spec, after another fuel efficiency device has been installed. In most cases, just the EFIE device, alone, may actually give you worse fuel economy.

The mechanics of this are that any time you add a technology to your vehicle, that improves the efficiency of combustion of the petroleum fuel you are burning, one of the results of this process is that there will be more oxygen appearing in the exhaust. When the sensors "see" this additional oxygen the computer interprets this as a "lean" condition, and incorrectly adds more fuel. This can severely reduce the mileage increase you will get from your combustion enhancement technology.

The EFIE solves this by adjusting the oxygen sensor's signal, to the ECU, so the computer is happy with the readings it's getting and it's making the correct adjustments for the various conditions of the engine.

Before we get into the details, please keep in mind that we recommend the Narrowband Series EFIEs for about 90% of all vehicles. We recommend these units for virtually all American cars, all foreign cars older than 1997, and most foreign cars after 1997. In the rest of the article we will cover why, and also the exceptions to the rule.

Basic Types of Oxygen Sensor

There are 2 basic kinds of oxygen sensor. They are called "narrow band" and the more modern, and superior, "wide band" oxygen sensor. The most important distinction is which of these 2 types of oxygen sensors you have. An EFIE made for one type will not work on the other. If you have any doubt about this point, you can contact us and let us look up your vehicle to be sure.

It is often easy to figure out what type of sensors you have. Is your car pre 1997? Then it's narrow band. Is it an American Car? It's narrow band (we've now seen a few wide bands 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 wide band sensors. Actually a very few cars started using wide band 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 wide band sensor. Note that Toyota and Honda uses a 4-wire wide band oxygen sensor. All other makes use 5-wire or 6-wire wide band sensors.

Here's another way to tell: Open your hood. Now look up. Do you see a sticker up under the hood with technical data about your vehicle? Often if you have wide band 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 wide band oxygen sensor.

One other point: If you have wide band sensors upstream of the catalytic converter, you will still have narrow band sensors downstream. As of this date (2009), we have never seen wide band oxygen sensors being used downstream.

Number of Sensors

The next point is, "how many sensors do you have?". V-6, V-8 and larger, usually have 2 sensors that are upstream of the catalytic converter, one on each exhaust manifold. Further, they will have 1 or 2 downstream sensors as well. Note: some pre-1996 vehicles don't have downstream sensors. Vehicles with 4 cylinder engines usually have 1 upstream sensor, and 1 downstream sensor. You will occasionally run into some oddball configurations that vary from these, but these are the usual configurations.

We recommend that you treat all oxygen sensors regardless of whether they are upstream or downstream. Many manufacturers are now using the downstream sensors in their air/fuel calculations, and others are using them to check the function of the upstream sensors, causing odd trouble lights and poor mileage gains. Because this has become so prevalent, these EFIE units are designed to include EFIEs for both the upstream and downstream oxygen sensors. These products include the correct combination of EFIEs to treat both your upstream and downstream sensors.

For instance, the Quad Narrowband EFIE has 2 digital EFIEs for treating 2 upstream narrow band oxygen sensors, and 2 analog EFIEs for treating 2 downstream sensors. Using analog EFIEs on the downstream sensors was not a cost saving consideration. We have found that analog EFIEs work better on downstream sensors, while digital EFIEs are clearly superior working on upstream sensors

For those who have wide band sensors, we have a similar product, theQuad Wideband EFIE, where 2 Wideband EFIEs for the upstream are combined with 2 Analog EFIEs for the 2 downstream sensors. Both the Wideband Quad EFIE and the Quad Narrowband Digital EFIE, come in a version designed for 4 cylinder engines too. These have 1 EFIE (either Wideband or Digital) for a single upstream sensor and a single analog EFIE for a single downstream sensor.

Have Questions? Contact Us

We know it can be a little confusing at times, trying to figure out what device is best for your vehicle. If you would like help with this, you can contact us, with the information on your vehicle and we will see that you get the product you need. We will just need your vehicles, Year, Make, Model, its Engine Size, and what country you drive in, if outside the US. Sometimes its just not clear which EFIE you need from the information you have available. In such cases, let us help you.

You May Not Need a Diagram

The following document has the wire colors for the oxygen sensor for many models of car. We've found this Oxygen Sensor Wire Colors page to be particularly useful. Be sure to magnify the image by clicking in it, for clear reading. Once you have identified the signal wire on the sensor, then go back to where the sensor wires plug into the vehicles wiring harness. You need to do this to find out what colors are used for the same wire in the vehicle's wiring.

Repair Manuals

When buying a new or used car, getting the vehicles repair manual for it is always a good idea. Included in these manuals are the wiring diagrams and the color codes for all of the sensors. There are several to choose from Haynes, Chilton's, Clymer and others will all be similar with the information contained. But we have always found Haynes to be the most informative. These manuals cost $20, which is generally money well spent. They are usually available from your local auto parts store, or you may even find a copy off of eBay. There are a few makes and models that they don't cover, but they have a manual for most vehicles sold in the US. For vehicles outside of the US, you can also ask an auto mechanic or your vehicles dealership. You also might want to try finding your manual on eBay, or even see if your local library has it.

AutoZone

Next, see if you can find your diagrams for free at AutoZone. AutoZone posts wiring diagrams for many cars and trucks for free. It also has a vast amount of repair information, including diagrams of part locations, detailed instructions, etc. If you don't have a repair manual for your car, you can just about get by with this all by itself. However, not all cars are covered by this service. You'll just have to look and see if yours is.

To see what they have for your vehicle, go to the AutoZone. Select "Vehicle Page" from their site. Then select the Year, Make, and Model, of your vehicle. You may have to register, as you may not get all of the same resources without registering. However, by registering, you can save your car's information. So, when you login again, all of the information is there without having to re-navigate the car selection.

If you have a hard time finding the wiring diagrams, to specifically find those, do the following:

1. Locate your Vehicle, Year, Make, and Model
2. Select "Repair Info" at the left side of the screen
3. Then select "Vehicle Repair Guides" -> "Chassis Electrical" -> "Wiring Diagrams"

You should be able to locate the ECU diagram, oxygen sensor signal wires, all of the other sensors etc., including the MAP (Manifold Absolute Pressure) sensor, if it has one. For some vehicles you’ll find which kind of sensor (DC voltage or frequency type), and even resistances = what pressure in the ECU. The same goes for it's entry on the CTS (Coolant Temperature Sensor), what temperature = what resistance from the sensor. This will help you enormously if you need to do adjustments to any other sensors, for any reason.

Mitchell's Online Repair Manuals

If the above resources weren't able to help you, then you can get your wiring diagrams from Mitchell's Online Repair Manual web site. The way to do this is to sign up for their 1 week subscription. This is a one-time payment, and entitles you to access for 1 week. You'll then want to copy the wiring diagrams and save them for your future reference.

Note: Unfortunately, this service is only for models that are sold in the United States. Models that are not sold here are not covered by this service. This includes domestic manufacturers, that make models sold only in overseas markets, but not in the U.S. If you are aware of a similar service that supplies diagrams for foreign makes and models, please email us, and we'll update this article with the information.

Once you've logged in, you'll do the following steps:

1. Press their "Subscribe" button, then select your vehicle, and finally pay them to join their service. You only need to sign up for 1 week.
2. Select "System Wiring Diagrams"
3. Go down until you find the section "Engine Performance Circuits"
4. Copy these diagrams. All of your sensors will be included in this section.
5. If you want any other diagrams, copy and save them as well.

Copying the Images

The images can be copied with just about any image processor, even Microsoft's "Paint" program. Below are the steps for several image programs, including Paint.

If you use these images directly in your browser, you'll need to blow them up. You'll see a link at the top "Click Here for full size versions". However, you don't need to blow them up when copying the images. They'll copy full size by using the following instructions. In each case, in the instructions below, you're going to open an image editing program, and then drag the image from your browser and drop it on the image editor.

(In case you don't know how to drag and drop, you put your mouse over the diagram in your web browser and push down the left mouse button. Hold the left mouse button down and move your mouse over your image editing program. Then release the mouse button. The full sized image will be copied into your image processor.

Below are the specific steps for 2 programs:

Microsoft Paint

You must do each file one at a time. You can't drag a 2nd image into the Paint program until the first one has been resized and saved. For each diagram image, do the following steps:

1. Image -> Resize -> Set the Horizontal and Vertical sizes to 50%.
2. Save As -> Set file type to "jpg" -> Then name the file (if you wish) and save.

Generic Paint Program

This is a free program that you can download and install. It was originally written at the University of Washington, and is still maintained by some of the original authors. It is completely free, and it is much better than Microsoft Paint. To get the free download, go to http://www.getpaint.net/. Once it’s installed, open the program and do the following:

Drag each image you want to save onto the Paint.net program window. You can drag all of the images into Paint.net, and it will create a new file for each image. You don't have to save each image before dragging in another one. For each image, do the following steps:

1. Image-Resize... -> By percentage -> 50%.
2. File -> Save As… -> Save as type: jpeg -> Use 50% quality setting.