So lets just clarify what sets and what clears a service soon lamp . Setting a code , some codes will set every time there is and electrical fault in that circuit and the key is cycled (ie continuous monitors) . some codes only set when the enable criteria is met light catalytic , evap , and other codes that are looking for a mechanical reaction . So by disconnecting a battery you can clear a code then it may reset as soon as you key it back up . People don't realize just what dumping a battery can do and often it with cause more problems than cure . idle learn and adaptives for both fuel and transmission management . some cars or trucks really run poorly after a disconnect . My suggestion is to clear a fault code as per manufactures recommendations . for some that a dump and others require scanners . Most simple scanners do a pretty good job with this , for way less than a hundred bucks you can have one in the glove box . It's a pretty good piece of mind to be able to pull a code and determine via a phone call or even google that your car is safe to drive or if more damage can occur . It seems senseless to me to just pass some thing off as ok when catalytic converters are so expensive . If your willing to drive a 30-60k truck or car be willing to scan it.
