OBD-II code readers/scanners considered

I have been considering getting a handheld OBD-II scanner for use with Volvo (2007 model year), and am looking for advice.
I gather that there is a spectrum of answers, from $50 to $5,000.
What features are essential, desirable, or useless? Why?
What brands are good, are bad?
I have been google trolling, and one recommendation that comes up is that the reader should be CAN (or CAN bus) compliant. (CAN is a communications bus used to connect things together in a car.)
I do like the idea of recording while driving, and later graphing.
Likewise, having the reader contain the dictionary of codes, with the ability to update over the web, sounds almost essential.
The home computers are MacOS, which may or may not matter for this updating over the web.
Thanks,
Joe Gwinn
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it is critically important that you figure out which ones will actually read your car's data - they all read the P-codes, but it is the manufacturer's data you want to read. I use an AutoExray unit that was about $600 - the less expensive units just read the P-codes and didn't help me with my issues (which are bizarre issues unique to this particular series of cars and year). Call the vendors, look at hte web sites.
there are also units that work with a laptop that are worth considering, but I haven't seen anything that works with a Mac - but a PC laptop is cheaper than a decent scanner, so just buy a laptop if you want to go that way

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If the reader does not contain a code, I suspect a search on the internet will find it. So I would not pay much extra for having the dictionary contain the codes. A shop would have more use for that since it saves time.
Dan
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Joseph Gwinn wrote:

You aren't likely to find scanner software that works with a Mac as the market of Mac users who also DIY auto work is exceedingly small. You should be able to find a used Wintel laptop quite cheap ~$150 that will work just fine with the scanner packages since they don't require much horsepower. Take a look at the "auto enginuity" scanner package, it has it's limitations, but will do your code reading, clearing, display / graph live data, log data while driving, etc.
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What's important is that it be compatible with the physical layer used by your car -- at one point, there were three different physical layers, all of which could claim to be OBD-II. While I think CAN is universal now, you'll want to check that.
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Joe: Make sure the reader that you decided on is fully compatable with Volvo's interface. VWs require the use of VCDS to do any adjustments within the computer system on the car and standard OBDC-II readers can only access the standard P codes in the system VW's system reports out over 10K more codes that the readers can't dechipher. Don't know about Volvos, but I do know that you don't want to drop the cash on a reader that won't do the job for you.
Craig C.
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Mine is an Equus Innova. I have the bottom end code reader, but a scanner is better. They seem to make quality stuff. They are a California firm, and their products are sold under several brand names. The ones sold by Canadian Tire here are just rebranded Innova instruments.
Steve R.

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I had an innova unit - no complaints about what it did, but it didn't read out dynamic parameters, and I absolutely required that (specifically engine power percentage) to do what I needed to do (my excuese for buying).
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I think I want dynamic parameters also.
I have some coworkers that drive fast Volvos and are likely to know what works and doesn't work. One of these coworkers may be modifying engine control programs (the latter day equivalent of changing the camshaft). I'll report what I find from them.
Joe Gwinn
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Don't even think about buying anything that does not support CAN protocol.
I'm not much help on the Volvo but I have used the aftermarket readers on a laptop. When they work correctly , it is so nice to be able to set the laptop up in the vehicle and drive down the road dealing with strange problems.
But the unit I borrowed (was planning to buy) did not have certain codes for the Explorer I was working on. An e-mail to the support folks showed that my software had been bought out by a new company, the seller was responsible for the code updates, the fellow never got around to doing what he was supposed to. End of story.
Moral of the story: if you need the special codes, make sure it works.
Joseph Gwinn wrote:

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