2003 GMC Truck OBD II CODES

Those codes applies to oxygen sensors could be it causing your problem if there not switching

rasmataz, thanks for the response!

I should have noted in my question that I am aware that both of the codes refer to the o2 sensors that are after the cats. What I don't understand is if it makes sense that both o2 sensors would quite at the same time or if there is a more likely suspect that could cause the same DTC's? I have just purchased a pc based scaning program and plan to use it to help me test the voltages, but I really don't think I have a good understanding of how all the electronics work together. Any additional help would be greatly appreciated.

A low voltage (lean) reading may indicate a bad O2 sensor, a vacuum leak, or a condition that allows unburned oxygen to enter the exhaust. Check intake vacuum at idle, and inspect vacuum hose connections. If okay, check for a misfiring cylinder, a burned exhaust valve that is leaking compression, or a leaky exhaust manifold gasket.