Scott
Anytime I have reset the ECU I have done so by dsiconnecting the battery for 15 minutes. This was on the advice of Andy.F who has been racing and tuning cars for years, so if anyone should know, he'll know. And yes, you do need to plug in a device to read off error codes, however, your CEL should come on and stay on if there is a problem. Have you tired all the usual steps, like checking all the hoses etc? Not long a go I had one tiny little hose come off and it threw up a CEL as it affected the fuel mixture. Your ECU can, to some extent change things when it thinks there is a problem, so clearing it will mean that its running under the normal parameters as the new stored ones will be lost. I had a cracked piston and the ECU retarded the ignition as the broken piston was detected as knockining. The retardation level was stored then when it happened again, the ignition was pulled back from the value stored by the ECU, so when I cleared it, I had a clean page so to speak. This of course never fixed the piston, but it just made the car more usable until I got it fixed. So that is what I mean by the ECU changing parameters. Give it a try.