Diagnostic Scan Tool

[oj88]

As mentioned, diagnostic scan tools are just that, scan tools. They basically allows you to see and clear DTCs whenever the CEL is lit up. Some can provide real-time engine runtime information like AFR, MAF/MAP, timing advance, ECT, O2 sensor readings, and a bunch of other stuff. More advanced scan tools also includes a data logger to allow you to view historical data. But suffice to say, a scan tool, per se, is generally used to get information OUT of the ECU. Think of it as an interrogation device for cars.

Although, some scan tools may also incorporate the ability to change certain parameters, these are usually limited to resetting the ECU, throttle position or assigning keys to the immobilizer and such. Example of these would be the Honda Diagnostic System (HDS) that's used in dealerships.

ECU tuning is whole new animal and can be done in various ways. But three methods are most common:

1. Replace the factory ECU with an aftermarket one that can be tuned or have has been pre-configured for performance
2. Re-flash the factory ECU to mimic an aftermarket ECU
3. Attach a piggyback (via DLC or physically spliced through the ECU connection). Some ECUs may need to be re-flashed or "cracked", if you will, in order to make this work

ECU tuning gives you the ability to remap and recalibrate engine parameters to maximize any performance parts you may have installed (ie. aftermarket injectors, intake, exhaust, turbos, etc.) and it requires a very deep understanding what each setting can do and how it affects the overall balance. You can actually destroy your engine if you dialed in the wrong values.

So, if a scan tool is to interrogation, tuning is to brainwashing.