OBD II code readers
 

May finally get into the 21st Century and get a OBD reader.
From those who use them, what features are valuable, and which are superfluous?

Autozone & Advance Auto will read codes for free. Why waste your money?

I have an OTC diagnostic computer. It was like $2,499 in 1999. I bought it last year, totally worth having. Fantastic tool.

I'd want it to be able to see what the ECM sees and not just read codes. Sometimes there are codes and they are created by other issues. I had a right and left bank lean condition code. MAF. If you can see the MAF output, you can make a more educated guess.

I've got a Scangauge that will read out most of the inputs to the ECM. I used it to identify a a bad cat by comparing the the voltage output of the front O2 sensor to the voltage of the rear O2 sensor. Other inputs that can be read are inlet air temperature, alternator voltage, engine rpm and many others. With a little programing real time mpg can be displayed. Benz switched formats at some time so the appropriate reader should be used.

Because there is a difference between simply reading the codes, and everything that might be available from the computer to help diagnose rather than simply throw parts at a problem.

I go to AutoZone and they give me about 2 feet of printout of ALL the possible sources. I want to know which of 12 possible components is giving out of spec readings.

Lets not forget the convenience of having it at home to diagnose at will instead of running down to the store, assuming it is open and borrowing the equipment which may or may not be available and may or may not be exactly what you want.

If you can afford it, buy one.

And +1 on the AZ units not being anything like a true diagnostic computer.

For what they cost today, I would think that the savings from tossing parts at a problem would more than pay for it. Not to mention the frustration of having to come back one more time to say "That part didn't fix it. Now what?".

No reader will give that information. You need the factory diagnostic computer for that-big bucks.

I see some that say " freeze Frame" or "graphing data".
Any idea what that sort of promotional speak really means?

Unless I am thinking of something else, it is a way to capture the data stream. When I used Diacom, it would allow me to capture say 5 seconds of data that the ECM sees. That allows me to put it up on a screen and slowly figure out what it means.

That gives data in real time as the car is driven. It won't do much for your desire of a machine to think for you.

freeze frame tells you what was happening when it threw the code.i carry my scanner in my suburban because if say i'm cruising along and have to hit the brakes all the sudden it will throw a pp420 code which is a bad catalyst.but that is not my problem.i can drive this thing for 5000 miles and if i don't have to get on the brakes hard it does not throw a code.i bought mine at o'reilly's for like 120 bucks.well worth it.

I have this one. Just make sure your car is supported. Generally you don't have to do any programming to see MPG, that is a standard guage. But you have to type in some stuff to calculate HP and read the O2 sensors I think.

If my CEL comes on I can check the code right away. I was driving and my alt light came on, I switched one of my gauges to voltage and could see exactly what was happening. Very nice. I can also monitor the condition of my MAF by checking the long term fuel trim.