my truck is an 02. from what i understand it has an extended warranty on injectors. how do i know when my warranty is up? when does it start? on sale date or manufactor date?

Your '02 has a 5yr/100k mile warranty on the DMax engine, that includes injectors. If you bought it new, it starts from the date of purchase. If you bought it used, then the warranty started when it was originally purchased.

If you got it used, you can request a VIN check on this site and find out when it was put in service and when warranty therefore started.

From chevy's website:
6.6L DURAMAX DIESEL POWERTRAIN LIMITED WARRANTY
For trucks equipped with the 6.6L Duramax Diesel engine, the complete engine assembly — including turbocharger components — is covered for 5 years or 100,000 miles, whichever comes first. This warranty also features a $0 deductible and is transferable to another owner at no additional charge.

WHAT IS COVERED
Cylinder block and heads and all internal parts
Intake and exhaust manifolds
Timing gears
Timing gear chain or belt and cover
Flywheel
Harmonic balancer
Valve covers
Oil pan
Oil pump, water pump and fuel pump
Engine mounts, seals and gaskets
Diesel Fuel Metering System: injection pump, nozzles, high-pressure lines and high-pressure sealing devices
Fuel injection control module and left and right common fuel rails- Glow plugs and control module

200,000 on the injectors for your 02

Call the dealer its the 8th # left to right that tells them what they need to know. I think your SOL on a 02 though.

I was told today by a local car dealer that my warranty on my 01 is 10yr 200,000 mile for injectors only

I stand corrected, I forgot that certain MY's of LB7 had injector issues that GM extended the warranty on. Sounds like 200k miles is the answer