P1345, ABS, Brakes, 4WD, a/c blower fan all fixed at once!
 

I just bought a 2002 Trailblazer a week ago via auction so had no history on it. When driving it had ABS, Brake, Service 4WD, Change Engine Oil, and Check engine lights on the dash. Also the a/c blower fan wasn't working and the 4WD switch showed it wasn't engaging though we could hear the motor underneath the car. A generic code reader only came back with P1345. Upon doing some research, my friend and I discovered there is another fuse box under the rear seat. The fuses for the above items were not receiving power to them. We introduced power and the lights went away, the blower fan started to work. The 4WD required the battery to be disconnected and reconnected and it too started to work. After more online research, I went and bought a new ignition switch and installed it. Not the part the key goes into, the part below it, a black plastic box that a ton of wires plug into with a gear on top that the key moves. It worked! Every light is the proper one that is supposed to be on and no warning lights are displayed. 4WD & fan are working fine. Who would have thought that an ignition switch would do all that?
Anyway, I'm new to this forum but I thought I would share this with you as maybe someone else has the same problem.
Regards, Rowanm77

Thank you. Usually when a problem is resolved on the BB or in your case you post a fix, often if an issue is posted with replies we never know if something suggested was a fix.

Explain just a little more please. I have a similar problem, but mine is intermittent sometimes they come on sometimes they don't. I don't have an Engine light or a change oil light though. Everything else is the same, when I can get the lights to go out by turning the ignition on and off, on and off, the blower turns back on the 4wd drive works. Where is this part located at? Next question, how much did it cost and who did you order it through?

2004 silverado 2500
 

In case anybody else has multiple electrical issues. My 2004 Silverado 2500 had several warning lights and Htr/Ac issues start all at the same time. Read this post and replaced the Ignition switch. FIXXED!!! Thanks for the info.

Hi All!!! Its great to be able to find info like this thread. My Envoy was doing the same thing with the instrument panel lights and no blower, but replacing the ignition switch module was just the ticket. All good now. Thanks for sharing the info.

Replaced the ignition switch. It fixed everything!!

Yes, I realize this is an old thread, but maybe someone else has the same question. The ignition switch is located underneath the ignition lock cylinder. You need to remove the steering column trim pieces to access it. They will cost around $45 -50.

​​​​​​I'm having the same issue and have been baffled. I've replaced grounds, blower resistor, etc. and still have the ABS, brake light, and service 4wd lights come on and then heater fan not work intermittently. My truck also stalls now and then. I didn't know what else to do into I found this thread. I'll update again once I've replaced the ignition switch.