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?

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1982 300SD " Wotan" ..On the road as of Jan 8, 2007 with Historic Tags

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

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1984 300SD Turbo Diesel 150,000 miles

OBK member #23

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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.

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01 Ford Excursion Powerstroke
99 E300 Turbodiesel
91 Vette with 383 motor
05 Polaris Sportsman 800 EFI
06 Polaris Sportsman 500 EFI
03 SeaDoo GTX SC Red
03 SeaDoo GTX SC Yellow
04 Tailgator 21 ft Toy Hauler
11 Harley Davidson 883 SuperLow

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.

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1982 300SD " Wotan" ..On the road as of Jan 8, 2007 with Historic Tags

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.

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01 Ford Excursion Powerstroke
99 E300 Turbodiesel
91 Vette with 383 motor
05 Polaris Sportsman 800 EFI
06 Polaris Sportsman 500 EFI
03 SeaDoo GTX SC Red
03 SeaDoo GTX SC Yellow
04 Tailgator 21 ft Toy Hauler
11 Harley Davidson 883 SuperLow

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?".

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01 Ford Excursion Powerstroke
99 E300 Turbodiesel
91 Vette with 383 motor
05 Polaris Sportsman 800 EFI
06 Polaris Sportsman 500 EFI
03 SeaDoo GTX SC Red
03 SeaDoo GTX SC Yellow
04 Tailgator 21 ft Toy Hauler
11 Harley Davidson 883 SuperLow

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?

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1982 300SD " Wotan" ..On the road as of Jan 8, 2007 with Historic Tags

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.

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01 Ford Excursion Powerstroke
99 E300 Turbodiesel
91 Vette with 383 motor
05 Polaris Sportsman 800 EFI
06 Polaris Sportsman 500 EFI
03 SeaDoo GTX SC Red
03 SeaDoo GTX SC Yellow
04 Tailgator 21 ft Toy Hauler
11 Harley Davidson 883 SuperLow

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.

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1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra