Anyone tried an OBD anlyser?

Question

Every car is now fitted with an OBD (On Board Diagnostics) socket.
This allows the user to check for faults.
There are anumber of devices available for this.

Who has experience of this?
Which OBD device gives the best clues to avoid being ripped off by garages?

Thanks to 'petrovitch m'. Good to know you use these too (in Russia?). 450 volts? That can do some damage.

Answer 1

Code Readers like those available in parts stores can tell you what the fault code is, some can even tell you what the fault code means, but none can tell you how to go about diagnosing and fixing the problem. All too many times someone will use one of these and pull up say, an O2 Sensor related code and go "ahah, I need a new O2 sensor", only to find that doesn't fix the problem.

The code just gives you the symptom. It does not tell you what parts (if any) to fix.

Let's start with the basics. The Powertrain Control Module in your vehicle is a computer that both runs and monitors all the functions in your engine For emissions compliance purposes when the PCM finds a problem with some facet of the engines operation that might effect emissions it triggers a fault code specific to the nature of the problem detected. When this fault code is registered and stored in the PCM the check engine light is illuminated. If it is a Type 1 or "hard" code, the light remains illuminated until the code is manually removed by using a scan tool or code reader designed for that purpose which plugs into the PCM. This same tool allows you to read what the code is.

Let's use an example of a very common code; A misfiring cylinder would trigger a P0300 Random Cylinder Misfire code, which you would then see on the tools display. Possibly, this same problem might trigger other codes too. Let's throw in a P0301 - Misfire in Cylinder #1, just for fun.

So you've hooked up a scanner or code reader and found the code(s). Now what do you do with this information? Does just knowing the code tell you what to fix?

Usually not!

The code just tells you where to start looking because what the fault code gives you is the symptom, not the cure.

Example; If I were to post a question here saying I had a P0300 and P0301 code for a misfire I bet I would get a dozen responses saying to replace the spark plugs. However, spark plugs are only 1 of many things that could trigger this particular code. If there is an individual ignition coil for each cylinder it might be a coil failure. Barring that, it could be a faulty ignition wire or spark plug tube (for coil-on-plug setups). On dual-overhead cam engines oil could be leaking from the valve cover O-ring that seals the spark plug hole in that cylinder. Or the fuel injector for that cylinder could be malfunctioning. But even then is it a bad injector, a clogged injector or a problem in the PCM itself which is causing the injector to not fire when it is supposed to? Perhaps a mouse chewed through the wiring harness for that injector (seen it more than once)? There are other causes too but you get the idea.

So, to find out why your check engine light is on you need to start by having the code pulled. This can be done at an auto parts store - often at no charge - but these guys are not equipped, trained or qualified to do the kind of diagnostics required to properly identify most problems. Even to find a parts guy (or gal) with a remotely useful knowledge of parts is a rare thing indeed. These folks use cheap "Code Readers" that cost just a few hundred dollars and that only read what the code is and don't offer any troubleshooting tips or diagnostic aids. Often they will do things like pull a misfire code and sell you some spark plugs that don't fix the problem. Or sell you an EGR valve because they pulled an EGR related code but that won't fix the problem either because a the EGR issue is the symptom, not the problem.

Or you could take it to a mechanic who has a Diagnostic Scanner that costs several thousand (up to $10k for some units) plus hundreds of dollars/year to update which can pull up not just generic codes like the cheaper readers but also vehicle specific codes. It can view everything that is happening in the engine in real time, see a snapshot of exactly what the engine was doing the instant the code was stored, has troubleshooting tips and specs for all of the related sensors, electrical components etc. He's not gonna do this for free. He's gonna want $80-150 for the pleasure but then, your chances of success are much higher. The problem may be a simple one, it may not, but its the expertise and the equipment your paying for.

Buying a code reader for personal use is I think a total waste. They don't tell you much and you will hardly ever use it. If you are dying to know what the code is for cheap should the light pop on, just go to a parts store that offers free readings. I would suggest being weary though of efforts to sell you parts based on those readings. Parts counter people are not diagnostic technicians and they don't have the proper tools to do that.

Answer 2

Sears has two which are both pretty good. You can also find the same ones a bit less new on ebay. Get one that comes with decoder software that provides the explaination of the code. If you are unsure, ask about a code on ask Yahoo.
Some garages charge $70 to determine that your check engine light came on because the gas cap was loose once and the light stayed on.
Autozone will loan you an OBDII scanner and you can check the codes and turn off the check engine light. This may be a better choice for yor first time so you can decide if you want to buy one or just borrow one. Somethimes, depending on the people at the store, they can be very helpful to interpret the code and get you the right parts to fix a problem.
Good Luck!

Answer 3

I own a shop, and I don't think you have to go to a garage to get ripped off. Matter of fact, you don't even have to go to a garage to get your OBD checked. Auto Zone does them all day long for free, and the ones they can't figure out usually end up at the garages. I can assure ALL garages are not rip offs, or they wouldn't stay in business very long. You can purchase your very own code reader for about $50 at most parts stores, and they even come with software you can install on your computer to tell what all the codes are. The OBD-1 computers were different, and required some expensive equipment, but since the introduction of the OBD-2 in 1996 there is no reason to pay anyone to get your codes for you, and to tell you what they mean. The problem arrives when replacing the sensor doesn't fix the car, and then you must go to a garage to determine the damage. To get these types of scan tools you must fork out lots of dollars to cover all the cars on the road, and get training in how to read and understand what you read from these tools. You would not believe the vehicles I have done computer repair work to that was caused directly or indirectly by a bad installation of a sound system, and/or related accessories. Sometimes it may take all day to find the problem, and someone has to pay for my time. If that is ripping people off then I guess I rip people off. Doctors do it all the time too, so unless you have the knowledge to make these repairs yourself, you better just get out your wallet and suck it up.
Glad I could help. Good Luck!!!
Part 2:
I would like to add to mine. Todays vehicles are not what they used to be. One must stay on top of whats new, and attend educational seminars that cover the new technology added for the new year, or he/she will be left in the dust. To maintain certification, one has to pass tests to do so. Everyone complains about the high cost of having their vehicle repaired, but it is only going to get worse. I wouldn't advise anyone to try to repair their vehicle by purchasing a code reader, and stabbing in the dark by throwing parts at a vehicle just because a certain code is showing. The vehicle manufactures are pressing toward throw away cars, just like throw away lighters that you can no longer refill. If anyone wants to place blame, then blame the manufactures, and the enviromental laws we now must live with. Getting a code is easy, but in order to pinpoint the problem, one must (almost always) monitor the data stream of each sensor, and understand what these values mean and/or should mean. A code that points you to which circuit the fault is in, does in NO way indicate that particular sensor is bad. You must know how to check this total circuit from the computer, to the sensor, and back to the computer. Ground faults, low refference voltage, and even interference from bad wiring like the shielding of a wire may be bleeding out to and/or crossing over to other circuits. I have even ran into a car that wouldn't run right because a circuit from the computer was too close to a spark plug wire. It then becomes hard to justify charging a customer for the length of time it takes to find the problem. It's easy to say you were taken advantage of in a situation of this nature. Any and all computer related problems should be dealt with by someone who has the equipment, and the education to use this equipment properly, or expect to be ripped off by unqualified shops that are parts changers, and not electro/mechanical technicians.

Answer 4

Depending on the make of vehicle then your dealer will have the best equipment for this. Halfords do sell cheaper versions, or get in touch with your local Snap-On dealer if you have more cash to spend. They all do the same job of reader any fault codes on the vehicle, but it aint always that simple eg, it may say its o2 sensor incorrect reading, which at first you may think thats the fault but could be a wiring issue or mush more, it not always straight forward, (trust me)

Answer 5

Some of the higher priced models have an L.C.D. display that will actually give the code and what it means. Others just give the code and you have to look it up in a book that is normally supplied with them.

Answer 6

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Answer 7

In mi cuntery we keep away OBD if is possible, they interogate, fingers break, put 450 volts inside, not nice. you avoid.