I have a stock 2003 DMAX. I have read a few threads where guys are already replacing the injectors? I have 40K miles on mine. How will know if they need to be replaced or not? Also, are these covered under any extended warranty from GM?

A lot of the early injector replacements were because of cracked injector bodies or ball seat erosion. Read the conditions and symptoms at this link here:

http://dieselplace.com/forum/showthread.php?t=18032

Injector replacement is covered by your 5yr/100K mile warranty for the engine. If an injector fails because of the conditions listed in the topic shown at the link above, I would be willing to bet you could push GM to warranty the injector replacement well beyond the 100K mile limit. (owners of 2001-2002 now have injectors warrantied to 7yr/200K miles for conditions listed in topic above).

The easiest test for an owner to conduct is to measure the balance rates using something like a Predator. The other test is to measure the fuel return flow from each cyclinder bank, but this is usually done at the dealership.

OC,

thank you for the info.