Is there a way to turn the light off on the 99 SSEi without actually disconnecting the battery cables or using an OBD-II diagnostic device?

finding out why the light is on is a pretty good first step towards getting it cleared... scan it

It was due for an oil change, just trying to find a way to get the light turned off without paying $ to have a tech use an OBD-II device.

if its ur oil change light then just turn the key on engine off and quickly press the gas pedal either 3 or 4 times, i don't remember exactly, then start it up, it should be off

there is NO oil change light on a Bonneville

you can go to Advance or AutoZone and they will scan the car for free...

be SURE to write down the entire code, then post it here for further assistance...

Advance Auto/Parts America group and Autozone do scan cars for free.

Well, AutoZone (in CA) apparently no longer scans it for free anymore, but that point is moot.

I have the lovely P0440 EVAP Emission Control System, which for most vehicles is a vague code. I erased the code and the engine light went off, and it hasn't come back on yet. In the case that it does come back on, what is the usual suspect on a 99 Bonneville SSEi for this code (don't say gas cap please)

The usual suspect you don't want to hear. Although I won't call it a gas cap. I'll call it a seal of the system. If the lip on the filler neck or cap are dirty, corroded.. clean them.

There are a few other areas as well, however that is the one that is removed and reconnected the most often. Ensure you aren't topping off or over filling the tank.