2003 Jeep Cherokee P0205 & P0305 codes

I own a 2003 Jeep Grand Cherokee Laredo: 4x4 with a 4.0L. Recently the above listed codes popped up on my computer. Naturally thinking it is an injector problem, I replaced the injector in cylinder 5. Unfortunately, the problem was not fixed. To ensure there was a good signal going from the harness to the injector, I used a noid light. The light was consistent with no gaps or pauses; there was a constant pulse. Does any one know where I go next?