duh oh! electric HELP needed

[poppa]

Hi all. Mama has a 06 trailblazer , when you hook up the battery ,NO key , it turns over by itself. Ghosts , I know. I pulled the ignition switch ,after I already ordered one , and found out it still does the same thing. Went and bought a manual only to find they only show 2 out of seven wires at the switch. Not sure if this means anything but ,  there is continuity between 2 in the harness that goes to the switch. The red one and the pink w/white tracer. I don't know where the pink one goes ,hence my problem. So many wires so little knowledge. Any help would be appreciated. Thanks (place emoji with shot glass here)

[Gold Rush]

Most likely suspect would be the start relay which is probably located in the fuse/relay panel under the hood.  It is also the easiest to pop out and isolated the starter solenoid (the second most likely culprit) control power.

When you pull the start relay check for continuity there.  The coil contacts will always read some resistance but the switch contacts should not read any continuation with NO power applied.  If the relay checks out, DO NOT reinstall yet.  Connect the battery and see if the engine still turns over.  If it does then the starter solenoid inside the starter is bad.

[poppa]

When the relay is out something on the firewall (or under dash ) "clicks" and the dash lights come on and the fuel pump kicks on. Will check when I get home if it's not raining. Thanks for the reply

[Gold Rush]

hummmmm....  That almost sounds like the Engine Control Module (ECM) is trying to wake things up.  Some of that is not unusual when battery power is first applied but I wouldn't think the fuel pump should get any power until the ignition switch is in the start or run positions.  Maybe the ECM itself is whacked??

[poppa]

is there a test ??

[b5blue]

Work off what this guy is doing for a "No crank" situation.    https://www.youtube.com/watch?v=iMzdYCA0s2w

[Gold Rush]

X2   Minds thinking alike...    I just found the same video.  Just having the diagram should be helpful.  Just have to think opposite of what the video is looking for due to their NO CRANK situation. 

[poppa]

Closer. With the relay out and battery neg cable disconnected , using a test light, I connect it to the neg battery post and check all 4 starter relay "holes" (female in fuse box) and I get power. The top left is brightest ,the other 3 not so bright. According to video one should be neg???

[Gold Rush]

Remember that video was chasing a NO CRANK problem while your is exactly the opposite so you can only use parts of the video as a guide.  Looking at a circuit diagram for a 2003 Trailblazer (same relay) battery power is applied to pins 30 feeding the relay contacts and either 85 or 86 feeding the relay coil.  When the ignition switch is in START position ground to either pin 85 or 86 energizes the relay sending battery voltage out pin 87 and on to the starter solenoid.

So, lets back up just a bit.  You have already eliminated the starter because it did not crank the engine with the relay out of circuit.  Now time to check the start relay itself.   Apply battery negative to relay pin 85 and battery positive to pin 86. Did you hear/feel the relay energize?  Check for continuity between pins 30 and 87. Is there continuity?   Remove power and check 30 to 87 again.  If there is no continuity then I'd say the relay is good. 

Refer back to earlier posts.  The next probably cause would be the PCM which actually is taking input from the ignition switch and sending the activation negative to the start relay.

Hope all that makes sense....

[poppa]

Relay tests good. Is a pcm the same as an ecm?? If that is my problem , does it need to be programed or could I use a used one? Can I do it or is that a dealer thing ?

[Gold Rush]

I hate to tell anyone "take it to the dealer" but we've used up all my troubleshooting.  I'm not positive the PCM is bad but it sure looks that way.  It takes some pretty high tech equipment to run diagnostics on these things and not many mom and pop garages will lay out that kind of cash. 

Here is a video of a guy swapping one out.   https://www.youtube.com/watch?v=yg1zcIfkUJY

[b5blue]

I feel your pain my 92 T Bird wouldn't start till the fuel pump cycled, sometimes 2-3 minutes. After having the pump replaced a PCM (Power train cont. mod.) fixed it. (30 bucks used on eBay.) ECM is electronics control mod. I have OBD 1 yours must be OBD 2 by that year, possibly Advance Auto has a reader you can rent?

[poppa]

What's a reader?? Unfamiliar with the whole pcm/ecm thing. Popping my cherry here!

[poppa]

Didn't think about this at first , it has an aftermarket remote start. Could this be involved??? Fob says Python.

[Gold Rush]

Possibly but hard to tell.  Only way to know is put everything back to original and see what happens.  I had an aftermarket shift controller cause the vehicle to go into limp home mode. The garage in Colorado ignored that I told them about it.  Cost me $400 and three days of my vacation time.  Live and learn...

[BrianShaughnessy]

Didn't think about this at first , it has an aftermarket remote start. Could this be involved??? Fob says Python.

Had an aftermarket remote start on the ex's malibu.   

It was great at first...  but after awhile it kept getting security errors and having to cycle the ignition after waiting 10 or 15 minutes or some BS with the car stranded in the parking lot at her job.

Yanked the remote start.   Fixed.

[poppa]

It was the remote start. Thanks all !!!

[Gold Rush]

We're glad you solved that mystery!!  Darn Gremlins!!!!! 

[b5blue]