can you have errors without any warning lights?

[ryan101]

just out of intrest can you get errors without any warning lights? eg like o2 senser stuffed or playing up?
or is it if there is sumthing wrong not matter what it is you will get a warning?

[IBLOWN]

Not all DTC's throw the engine check light but they are retrievable by using the diagnostic mode.

[ryan101]

it is due for a its first service since i brought it soon, it seems a bit laggy so i thought i will get the works done spark plugs fuel filter air filter maf cleaned and the usual oil and filter, aswell as get it hooked up to see if there is anything there i don't no about