Anyone have a oem wiring diagram for a GM 4.2? I've been trying to troubleshoot problems with my Trailblazer and the Haynes manual has nothing. They say to take it to an authorized service center. That was 30 bucks down the crapper.

I do but its a 1/3 of the GM manual (2" thick) by the time you wade through the comic book instructions. If you have a specific question I may be able to help - my manual is an '05

I can help with specific stuff too. PM me if you want.

I need help with the secondary air/emmission pump system. The best I can tell is that there is a relay on the main fuse panel that sends power to the relay mounted on the pump. What I'm confused about is, the manifold mounted solenoid and what triggers the relay on the pump. I'm assuming the main relay is controlled by the ecm. On initial startup, I'm getting control voltage to the pump relay terminal and voltage on the line side of the terminal. I'm also getting voltage to the solenoid, but it drops out as soon as I put the multimeter on it.

If I had a wiring diagram, I could probably troubleshoot it.

O.k. about 2 years ago, I replaced everything on the secondary air system; pump, relay, solenoid. Everything was good for awhile. Well my thermostat was sticking open, so I started getting a "not up to temp" code. Well after that was fixed, the secondary air code was back. I took the old pump off, and checked the terminations, everything was good. I put 12 volts to the pump. Wow! it was noisy and put out very little air. So, O'reilly warranteed my pump and I bought a new relay just in case. I put 12 volts to new pump, and it was like a jet taking off. So, all was good. Well, my fix only was good for a day, and the code is back.

I know the system is controlled by an engine temp signal via the ECM. Which is probably why the first pump went bad. Everything is new again. It should be working properly. The only thing I can think of is having O'reilly warrantee the Solenoid and maybe replacing the temp sending unit.

Any thoughts.