I am working on an 02 DTS N*.
Well it idles high, around 2000 rpms, when in park and when you put it in drive it will actually speed up to 20mph easilly. there is currently no check engine light on, but i did check for codes the other day, and there were a few codes for cruise control, Idle System, Fuel Level sugnal, and a couple others but I didn't record any of them becasue it ran fine.
he recently had an Oil Pressure Switch go bad (Message: "Stop Engine, Oil Pressure Low") replaced the swich and everything is fine, he also has the usuall N* oil leak (Rear Main seal, Lower Block Gasket, etc.), also about a month ago, i replaced the MAP sensor and replace a bad A.I.R. Pump. He said the light has been on since B4 I did the work, this is why i just erased the codes without recording them.