Question: 2005 Chevy Trailblazer, 6 cylinder the ABS, Suspension, Security light, battery, every light but the check engine light is on I have no gauges, oil pressure, gas, battery, water, rear wiper does not work, stereo does not work, windows do not work, interior lights come on and stay on. I have cleaned the battery terminal to the main fuse box.
I have pulled fuses and put them back after checking to see if they are burned. I am pretty sure it is a relay that has gone bad but which one and where do I or how do I find it?
Answer: You need to check the 125 amp mega fuse in the under hood fuse box, that the positive battery cable attaches to. Is it black, and you can't see if it's blown, you need to test with a test light or volt meter. There is also a fuse box under the left second row seat. Check fuses and relays there as well. Also, the Body Control Module is located in that position and if it is shorted out, it could cause all the issues you describe. You say every light is on but the check engine light, but does it come on when you turn the key on and do a bulb check? If you have no check engine light at all, even for a few seconds when you turn the key on, then you have a Powertrain Control Module problem. Something is obviously blown somewhere, and a single relay would not cause this problem like you are thinking. If you've had to jump the vehicle recently, you could have smoked one or more computer modules, wires or fusible links. You'll need to check it all.
Reply: Thank you for your assistance but still have not found the issue. The check engine light does come on when I start the trailblazer. Then everything works like it should then I begin to have the same issues. Everything but the check engine light is on. No power to windows, stereo keeps trying to eject, battery light is on, suspension light is on, abs light is on, all the same issues. If I have to drive and the road is rough it all starts working correctly but then goes off again. It is intermittent. I have checked with a test light everything you suggested, now what do I do?
Answer: Rough road may mean a loose or rubbing wiring harness somewhere. Try pulling on engine harnesses and the fuse block under the 2nd row seat behind the driver. Flip it up to get to the fuse box. The Body Control Module is also attached to it. Try moving that around to see if you can get it to act up. Then you know you are in the right area.