I have a 2002 trailblazer LS with a 4.2 I6. Truck ran perfect, but developed a rod knock.
So I purchaced the same year engine from a salvage yard with lower miles and installed it. Now it cranks but will not start.
I hooked up my EFILIVE tuning software and get these codes even immediatly after they are cleared.
-P1681-Control Module throttle position(tp) system
-P1635-5 Volt reference 1 circuit
Truck cranks but will not start, I smell fuel from the tail pipe, and both the CEL and Reduced engine power lights stay on.
Keep in mind, the truck had no lights or peoblems at all before I swapped the engine so I am not sure what could be the problem.
I swapped throttle bodies between the motors and still nothing.
Any help and ideas would be appreciated.