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CTS-V
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Discussion Starter #1
I've been having this problem since Thursday and I not anyone else I have asked (TBSS owners included) has ever heard of a problem like this. Car isn't stock; it has cam, headers, built trans w/trans cooler & stall, tuned, gears, etc.

Thursday morning my SS started doing some funky crap just out of the blue. When it's in PARK it won't crank at all. I turn the key and the battery powers everything on just fine, but the starter won't engage and the motor won't turn over. No click, no sound. Nothing. Yet if I leave the key turned on for the battery and throw the car in NEUTRAL it cranks totally on it's own without turning the key further, but it idles like [email protected] until you put it in gear then it idles fine. I can then put it in Park, Drive, Reverse, etc no problem and it drives just fine. However, if I shift back through neutral it grinds the starter.

I have already replaced the ignition switch and the neutral safety switch and it didn't resolve anything. I have been told so many different things that I don't know what to check first. I have been told it's a bad ECM, bad fuse box, bad starter (false), or possible bad BCM. I haven't had the opportunity to bring it to anyone knowledgable yet other than car savvy friends and one TBSS owner.

Another thing is that I hooked a computer with HPTuner software on it and it's throwing the P0615 - Starter Relay Circuit code. Checked the relay and replaced it and nada. Relay was extremely hot though. The computer showed that the car thought it was in 1st gear at all times (even in neutral) other than when shifted into 2nd gear. Not sure if this is normal as I have never hooked something like this up to the car before.

I'll allying the guys that tuned it first thing in the morning but I need to know if anyone else has experienced this at all because I am totally lost and NO ONE has ever come across this or knows how to fix it.
 

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Premium Member
'08 TrailblazerSS
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2,987 Posts
It kinda sounds like maybe your starter relay control wire is being shorted with one of the trans range switch wires which is causing your starter relay to engage when you shift to neutral.
 

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Registered
CTS-V
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Discussion Starter #3
That would cause this whole thing? The not cranking in park and thinking it's in gear when in neutral? And the fact that it cranks itself without touching the key when in neutral?
 

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Premium Member
'08 TrailblazerSS
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2,987 Posts
When you shift to neutral and the starter automatically engages, what gear does the gear indicator show?
 

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Premium Member
'08 TrailblazerSS
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2,987 Posts
Ok. That tells me you have some sort of short on your starter relay control wire. The ecm actually controls the starter relay, not the ignition switch. The ignition switch sends a crank signal to the ecm. The ecm then applies ground to the starter relay to engage the starter. The ecm will only engage the starter if the truck is in park or neutral. Since the gear indicator is showing 1, that tells me that the ecm is not commanding the starter on. So whenever you shift to neutral, ground is being applied to the starter relay control wire, bypassing the ecm's control, which is causing your starter to engage.
 

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Midgets with hammers
'06 TBSS AWD
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15,999 Posts
What BranndonW is saying makes absolute electrical sense w/o looking at the schematic, which he is. A short can be a bitch to find, but to test this, run your own wire from the pin he tells you to, to the starter control relay. When this works, you still have two chaffed wires to fix. Your other option is to TDR the wires. A Time Domain Reflectometer will read your lines and tell you how many feet down the line the short is, then you measure and find it. Good luck and let us know where you find the chaffing.
 

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CTS-V
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Discussion Starter #10
Brandon, that makes sense. I did some reading on it last night and tried the paper clip in the relay trick and it fired right up no problem. So I'll be replacing my fuse box but if this issue comes back up then I'm going to try to find someone to help me find a short in the wiring for the starter relay.

Kyle, you have no idea how many times I have seriously wanted to.
 
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