The USB OBD II Computer Cable—How to Use It, What It Does, and How to Make It Work for You!
When the check engine light device was started, it was intended to help control vehicle emission to help protect our environment. Now, almost everyone has an OBD II port in their cars. We use these ports to get trouble codes (also known as check engine lights and "CEL") and diagnose our vehicles.
What a lot of people don't realize is that we can do much more with our OBD II ports than find out if our engine is having trouble. In this article, we're going in-depth about exactly what OBD II ports are and how we use them today.
OBD II Code Readers: USB vs. Hand-Held
OBD II has come a long way since 1996 and we now have the technology to own OBD II code readers in our home and office. You used to have to pay a pretty penny (upwards of $50) just to get a code read, but in today's modern world you can get your own basic OBD II code reader for that same price.
It's still true, however, that you get what you pay for. That said, the average DIY mechanic won't need anything too expensive when it comes to a new code reader. You can buy a basic hand-held OBD II code scanner for around $50 from your local auto store or retail store (or even cheaper on Amazon). However, with technology comes new ways of reading your trouble codes and now your personal laptop (equipped with a USB OBD II cable and the proper software) can do all the work for you.
I'll go into some of the basics of what hand-held readers can do vs USB laptop readers and my opinion on them both.
Hand-held OBD2 Readers
Lets start with the hand-held OBD II readers. For a basic code reader that can read check engine lights, give you the codes (though they don't usually tell you what they mean), and erase them for you, you're looking at around $50 at a retail store or maybe $38 shipped from an online vendor.
These are very basic and only tell you what codes you're getting and can clear the check engine light for you. A decent ODB II code reader can cost anywhere from $90 - $200 and they have more data capabilities, such as showing you the freeze frame, which is the captured data that is stored about important sensors at the time a check engine light is triggered. Freeze frame data can show you exactly where a problem is if you understand how a car works and use your knowledge about the symptoms you're experiencing with the CEL you're receiving.
Using a USB OBD2 Code Reader
However, a few years back, people figured out how to create USB-driven OBD II cables which hook up to your laptop and can check sensor data and do anything else a hand-held OBD II code reader can do. They can actually do a bit more with the proper software. For half the cost of handheld and the ability to do more, it sounds promising enough already, right?
One of the better things about the USB OBD II cables is that you aren't limited by the cable, as in one is not better than the other, it simply serves as a link between your computer (which does all the work) and your OBD II port in your car (which will be sending all the data).
For roughly $20 dollars you can get a USB OBD II cable on Amazon or you can try your luck on Ebay. However, you will not find one in your local auto or retail store. Just remember, unless the cable is absolutely poorly made or damaged, there are hardly any differences between one USB OBD II cable and another. The software is what matters! I'll cover that below.
OBD II Software for the Computer
Like anything else, you get what you pay for! There are literally tons of OBD II scanning software that is out there. Some of it's free and some of it costs a good chunk of money. I'm going to briefly talk about a few products, what they do, what features they have and most importantly, how much they cost!
ScanTool — An Expensive but Well-Known Product
Price tag: from $65.99
One of the better known lines of OBD II software scanning products is called "ScanTool" and you can find all their programs and OBD II USB Cables over at www.scantool.net. They actually have a whole line of different types of products, from specially-designed products for different car manufacturers, touch-screen based programs and even your basic checking and clearing codes programs. Their programs range from $25 to roughly $130, with more for add-ons you can get, not to mention their specific OBD II cable for your computer. Not bad, but you can get a very good tuner for about the price of their "full setup."
ProScan—The One I Use
Price tag: $39.99
Another quality program is called "ProScan" and it's actually the one I use on my laptop. This does work with a generic USB OBD II cable as that's what I use. This program is very nice and has just enough features to keep me interested in it and not just as a "okay, time to get the laptop to check the codes" type of thing.
It tells you what codes mean in plain English so you don't have to spend time Googling whatever code you received. It clears codes quickly and has monitors for pretty much any sensor you can imagine. It has an HP/Torque estimator and can even give you pretty accurate 1/4 mile times. Although I suggest if you want to use either of these features, you do it in a safe environment with few people.
EasyOBDII—The One I Recommend
Price tag: $19.99
The last program I'm going to talk about is called "EasyOBDII." It's a rather good program and was one of the first ones I found and tinkered with. It gives you some pretty good sensor and other kinds of car information. However, there is a very limited free trial which only lets you just about read codes and do a few other small things -- you can't even clear your CEL with it unless you have a paid version.
However, the very good news is that a commercial license only costs $19.99! I'm not positive, but I believe that the commercial version unlocks everything you should need (and more). The best bang for your buck is probably with this program and the fact that you can get the free version and mess around with it to become familiar with the program is a very good marketing strategy.
To be honest, I do love ProScan, but if I hadn't snagged a free copy of it, I would have definitely bought EasyOBDII for a mere $20. However, my best suggestion would be to research, research, research and come to your own conclusions. My opinions are simply that, my opinions! Make sure you can understand and work the software before you even begin thinking about getting a USB OBD II cable!
Background: What Is an OBD-II Port?
OBD is actually short for "On-Board Diagnostics" and, like the name suggests, it gives you diagnostics on your OBD-II equipped car. Not all cars have them, but if your car is from 1996 or more recent then it almost certainly does because as of 1996 it was required by law. There is a chance that your pre-1996 car has an OBD II port, although you would have to physically check to be sure.
What Are OBD Systems?
First, a little history on the OBD port and what it is. On-board diagnostics, or OBD, in an automotive context, is a generic term referring to a vehicle's self-diagnostic and reporting capability. OBD systems give the vehicle owner or repair technician access to state-of-health information for various vehicle sub-systems. The amount of diagnostic information available via OBD has varied widely since their introduction of on-board vehicle computers in the early 1980s in which made OBD possible.
In 1985, OBD I was introduced to standardise the way in which vehicle computers could be monitored. The list of functions that OBD I was able to do grew with the need for real-time misfire detection, catalytic converters, Lambda sensors, and fault code capability.
After the OBD-I, the little known OBD 1.5 was released. This was almost like a beta version of OBD II. General Motors used it in some 1994 and 95 vehicles. Post-catalytic lambda sensors were fitted and the standards that dictated OBD II brought us the P Code (Trouble Codes).
Finally, in 1996 OBD II was introduced and with this came the 16-pin diagnostic connector that we see today. The OBD II standard specified the type of diagnostic connector, the messaging format, and the way in which the electrical signaling protocols would be wired to it. The OBD II standard also provided an extensive list of diagnostic trouble codes (DTC's) As a result of this standardization, a single device could query the on-board computers in any vehicle.
The OBD-II specification provided for a standardized connector, the female 16-pin J1962 connector. Unlike the OBD-I connector, which was sometimes found under the bonnet of the vehicle, the OBD-II connector is nearly always located on the driver's side of the car often close to the steering column.
SAE J1962 defines the pins out of the connector as:
- Bus positive line of SAE-J1850
- Ford DCL(+) Argentina, Brazil (pre OBD-II) 1997-2000
- Chassis ground
- Signal ground
- CAN high (ISO 15765-4 and J2234)
- K line of ISO 9141-2 and ISO 14230-4
- Bus negative line of J1850
- Ford DCL(-) Argentina, Brazil (pre OBD-II) 1997-2000
- CAN low (ISO 15765-4 and J2234)
- L line of ISO 9141-2 and ISO 14230-4
- Battery voltage
Unspecified pins (marked with a "-") are left to the vehicle manufacturer's discretion which can be connected to a model's specific systems.
What Trouble Codes Mean and What to Do About Them
If your car is "throwing a trouble code," e.g. the check engine light is on, then this is a job for your OBD II equipment. It is the same as the "Service Engine Soon" light (SES) or the "Malfunction Indicator Lamp" (MIL) light which are displayed in your vehicle. Your OBD II code scanner or even your laptop computer can tell you exactly why your check engine light is on.
The check engine light comes on after a period of time when your computer is sensing that something is going wrong (or "out of spec"). When your check engine light comes on in your dash, this means that the vehicle engine computer (ecm) has stored some electrical signal indicating that your engine has a problem that can affect engine performance, drivability, stability, and/or gas mileage. Most of the time, these trouble codes are important to check and fix immediately.
However, there are some exceptions to this. Just because you see the CEL does not automatically mean that the engine itself is at fault. For example, if you accidentally unplugged a vacuum hose, left a coil or plug connector loose, or even left your gas cap off by accident, chances are it will set off the CEL. The proper way to analyze a light is to scan for codes and analyze it based on the engine symptoms.
If you have retrieved your code (or had a mechanic or auto store retrieve it for you) it's time to figure out what it means! I would suggest looking up your codes on the OBD Codes website for the best accuracy across all makes and models of cars.
My Personal Views on USB vs Hand-Held OBD II Code Readers
As a typical "DIY" home mechanic, I enjoy working on my car and when I have the spare time I do whatever maintenance I can on it. I've had check engine lights come on before and have had the pleasure of using multiple types of OBD II code scanners in order to figure out what went wrong with my car.
My First Hand-Held OBD II
The first one I used was one I found at Wal-Mart for $56 after tax and it didn't do too much. It displayed the codes to me and I could browse the other codes and erase them. If I wanted to re-read the codes I would simply click a button again (a total of three buttons were on the reader) and it would display any codes again. That was it. For $56 I felt that this was a little too basic for me and all I needed it for was a one-time read, so I took it back after I figured out what the codes meant, since the OBD II code reader didn't tell me.
My Second OBD II Code Reader
Then, I tried a buddy's Ebay OBD II code reader. He didn't specifically say it was from Ebay, but it was very much like the one I had, but smaller and with a tackier setup. He plugged it in and said it was weird because it had actually given him "F" before the codes, which he "never saw before" but if I had to guess, it simply meant that the code was a Ford code (the codes can sometime vary between different makes of car) and considering I have a Mustang, that made sense to me.
His code reader also decided to make up a P0000 code, which I couldn't find on any type of database nor manage to bring up on any other OBD II code scanner. However, it did let you scroll through the codes and clear them, much like the one I bought from Ebay. It was the same basic setup and abilities, although I'm sure he paid about half of what I did for mine.
After I sent my friend on his way and fixed the problem (or so I thought) I managed to still have a code or two left (there were a few codes strung together due to an important fuse blowing) so I tried to find a cheap reader I could order. I wasn't going to drive my car again for a few days, so it could sit while I waited for the new one to come.
My First USB OBD II Cable
I searched Ebay and found tons of the USB OBD II cables and decided, "Hey, if I can find some pretty good software, why not?!" so that's what I did. Even though the majority of the USB OBD II cables come with software, they are usually limited or trials. Also, the sellers are all Chinese sellers and if they're located in the U.S., I guarantee they are reselling the Chinese cables, at least, my seller was. The cable came pretty quick and I recommend you buy from a U.S. seller, although you'll pay more obviously, but that's up to you.
So the day came that I got my cable and I was thrilled. I checked out the included software and Googled all I could for free software and it seems that the free stuff you can get is very limited, usually to the point where you can't even clear the Check Engine Light, although it will tell you what the code is AND (drumroll please!) will tell you in plain English was the code means!
What this means is that instead of seeing a P0307 code, it will tell you the code plus "Misfire on cylinder #7" since that's what a P0307 code means, so you don't have to go look up what the code means which saves time and trouble, and allows you to get to work immediately.
I managed to get a pretty nice program through a connection and I really like it. I can quickly and easily connect my USB OBD II cable right to the car from the computer and access any check engine light data (even pending codes), view live data, get an estimated 1/4 mile time, and even get HP/Torque readings (although the two latter seem to be a bit finicky and requies some messing around with).
Overall, for a mere $22 for the USB OBD II cable, I am very pleased with everything the software allows you to do and view. I bought my cable months ago and have used it constantly, even if it's just to help me monitor data. It's a great tool and I highly recommend it. However, if you don't have a newer laptop (or a laptop at all) I would stick with a hand-held one as it would probably be quicker and easier for you.
It all depends what you need and want out of an OBD II code scanner or if you want tuning capabilities, which I haven't found any decent software for yet under $500. At that rate, you can just buy a custom tuner for your vehicle. It's up to you!
OBD II Related Products - We All Need Them!
Did you know it could cost up to $50 for a shop to "diagnose" your check engine light?
Save money on the diagnosis and do it yourself! Pay for a code scanner and it will pay for itself on your first CEL!
Basic USB Reader
Video: How to Use an OBD-II Scan Tool
Got something to say? Say it! I welcome all comments and hope I was able to help you out!
buddy adams on December 08, 2017:
im looking at buying a laptop and a usb/obd cable im looking to adjust perementers on my hotrod and scan cars trucks and some commercial trucks also what do i need
wrench on October 07, 2015:
I believe the p0000 sets when all criteria have not been met to pass emmissions. This code sets when you clear codes, and only goes away after all emission related tests have run and passed at least 1 time.
peter crowther on September 28, 2015:
hi my peugeot boxer 2001 has a green 2 pin plug and next to it a 3 pin plug . how can i make a turnaround for the OBD 16 pin
robertjackson on July 15, 2015:
The OBD 2 cable and the entire software and interface are used for thorough engine diagnostics. There is definitely a complex mechanism working behind OBD. The male plug is connected with the computer in the car while the female plug is connected to a series of car components for which proper checks are conducted. The OBD 2 sensors collect any information from the car and transfer the same to the computer through the Obd2 Connector.
Johnlee on April 24, 2015:
I liked it I've been trying to understand can buses because of a problem with my Hemi ram but I am looking for diagnostic software to use on dodge,ford and Chevy diesels I want their data on my laptop also my big dog motorcycle .use the laptop for more than a music movie platform I saw a laptop on a hotrod once and wanted the setup ever since give us more of this type info thanks jl
electronic spark on March 05, 2015:
Tried CarPort v2.2.7 on windows8. Wouldn't find my usb cable. I tried it then on xp and wouldn't even start, complained about some dll.
electronic spark on March 04, 2015:
What software you recommend for manufacturer specific diagnostic like vw airbag and brake. I have a cable and Ross tech free software version but it doesn't work very well. After many tries and resets i get a couple of seconds of connect time. Not quite enough to check code and reset intermittent airbag for example.
DaniellD on April 29, 2013:
Great article, I really liked it.
I think it would be nice if you had a list of engine codes and what they mean, or at least links to sites that offer engine code decoding like
but overall it is very informative and useful post, thanks
squmarini on January 26, 2013:
Good information. Tnx.
anonymous on January 13, 2013:
Hi man! Thanks for this very very useful post. It helped me to learn on it and decide which OBD-II to USB cable to buy!
BrianLGilman on November 19, 2012:
Very informative... A very confusing subject for most people including myself. Thanx for clearing the issue up a bit.
anonymous on October 31, 2012:
i am maxwell,i wanna know where can i get that OBD II cable? And does it come with the software? I am from south africa. Email: firstname.lastname@example.org
anonymous on August 18, 2012:
Very, very nice post, thanks a lot for this information !
I have a little question: you can change the parameters of measure, like, the mpg could be changed in the software to km/L, for example ? I'm from Brazil and here we use IS units. ^^
Thanks again !
tyang21 on May 21, 2011:
I use on and it has saved me hundreds doing the stuff myself. Obd ii scanner