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A Dose of Digital: Part 1 - The Basics - Page 4 of 5

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© 2010 by Hib Halverson
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Scanning for Information

All 81-'10 Corvette ECMs transmit engine controls information over a "serial data link" which has a pin in the DLC. To see that information, you need an "off-board" device which can "scan" this serial data. Such devices take two forms: 1) a hand-held diagnostic computer called a "scan tester" (also a "scan tool" and for short, a "scanner" or a "tester"), or 2) scan test software which runs on a personal computer.

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When we're doing diagnostics, we prefer a scan tester, in this case, the Bosch MTS3100 Mastertech. Not only can a Mastertech display codes but it performs other tasks which make a DIY tech's job easier. We'll talk more about testers in the later parts of this series.
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There are, also, many software-based scan test applications which run on personal computers. Shown here, running on our Acer 5670, is EASE PC Scan Tool v8.0, which we think is pretty good scan test software. You'll read more about EASE in later in this series.
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Generally, a scan tester or scan test software is the best way to interface with your Corvette's on-board diagnostics. This is especially true for OBD-II systems. Like the various on-board display methods discussed previously, scan testers read DTCs. Testers, also, do what on-board display systems can't: show engine control parameters in real time, record "snapshots" or "captures" of data-a feature quite valuable in solving problems which are random or intermittent. With OBD-II scanners can display the system's failure records, a limited history of conditions present when a DTC sets. Lastly, a few scan testers are capable of "bi-directional" communication and can control of certain ECM functions for diagnostic testing or new component initialization purposes.

A lot of diagnostic work at the Corvette Action Center is done with a Bosch Diagnostics Mastertech (PN MTS3100) which is the tester the Santa Barbara, California company currently markets to non-dealer, service trade users. For this article, we used the Mastertech on Corvettes from: '81, '82, '89, '91, '92, '93, '95, '02, '04 and '09. We also scanned a '99 Blazer, an '01 Camaro, an '03 GMC Diesel pickup and an '07 Chevy HHR. Suffice to say: Mastertech works with just about any GM vehicle and, because of that, it's our choice in hardware-based testers.

Some scoff at the seeming frivolity of professional-grade equipment for DIY work, but trust us-wit the number of cars we work on, diagnosing the on-board computers of Corvettes and other GM vehicles is easiest with a Mastertech, or its brother, the TECH 2, GM's dealer scan tester.

That said, there are less expensive alternatives to pro-grade hardware and we will cover some of those diagnostic devices in future parts of this series.

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