What is a code 27?

I just recently bought a 1993 GMC Safari and after driving it for a while it starts to act up and when I check the engine codes I get a code 27 but it is not in my book can anyone help me?

Don't see 27 for this engine.

I know everyone I've talk to says the samething and it's isn't in my book either but that's what is coming up when I do a code read

http://www.troublecodes.net/GM/

27 throttle switch open

Not sure if this applies to you or not, but this is listed under the generic codes.

//2000CAYukon