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Go Back   Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum > 2002 - 2009 TrailBlazer/Envoy Tech > 02-09 General Tech Q&A > General

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  #1  
Old 05-20-2011, 07:43 PM
Cureact Cureact is offline
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neutral safety switch help

Ive been looking for a write up on replacing the neutral safety switch and I havnt been able to find it or any help. If someone could direct me that would be great and ty very much.
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  #2  
Old 05-20-2011, 10:12 PM
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I don't recall seeing a write up, why do you think you need to change the switch?
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Old 05-20-2011, 11:15 PM
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Quote:
Originally Posted by RayVoy View Post
I don't recall seeing a write up, why do you think you need to change the switch?
Ah hahaha had to ask hu....Well the wife and I were fighting.....and in her infinite wisdom and her temper decided while we were doing 55 on rt 17 she then decided to slam the shifter into park while I was driving....smart hu lol. So the next day I got in the truck and 2 things happened. 1 .....key wouldn't turn. I had to break the lock then ....well lets just say allot of anger lead to a whole new ignition and the other parts around it lol. So all happy I try to start it ...nada ....heard a click but nothing....so I pull the starter get it tested and its good. ( thank god those suckers are $200) Well so ive gone to the neutral safety switch. I did find it and get the old one off but having a hard time fitting the new one cause of the drive shaft in the way lol.....I am a shade tree mechanic at 40 years old who sometimes causes more problems than fixes lol....so that's why I decided to come to you guys. For the love of god please help lol 4 weeks and the kids and wife are driving me crazy.....For all I care let the truck sit there for $4 a gallon I can ride my 6x 6r 636 ninja all over but now there killing me lol.
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Old 05-21-2011, 12:13 AM
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The neutral safety switch (now called a PRNDL switch or a MLP sensor -manual linkage position sensor) is # 15 in the diagram....how is the driveshaft in the way?

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Old 05-21-2011, 03:32 AM
Cureact Cureact is offline
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I will take a few pics tomorrow. I am assuming it is the shaft in the way for the PRNDL to be able to go in properly. With what I described sound like what the problem might be ?
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Old 05-21-2011, 11:20 AM
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There are a few components related to the Starter circuit.

IGN A #34 fuse 40A Front fuse box
Starter Relay #47 Front fuse box
Ignition Switch
IGN E #22 fuse 10A Front fuse box
CRANK #17 fuse 10A Front fuse box
Park Neutral Position switch (PNP)
PCM
Starter

I agree, the PNP switch is the most suspect here, after fuses. There is a dedicated set of contacts for the start function. I'm surprised that if you could get the old one off, that the new one won't go on.

For further troubleshooting, Check the fuses and swap the Relay with another of the same part # (don't remember if there is another identical one though).

There are 2 items that can "click" when you turn the key, the Starter solenoid and the Starter Relay, (could be others not related to starting that cycle when you turn the key to start).

Once you have checked the fuses with a meter, you will probably need a schematic and that meter to continue troubleshooting.

Hope this helps.
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Old 05-22-2011, 02:36 AM
Cureact Cureact is offline
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oh lord an baby Jesus.... replaced the switch and still nothing .......I dont understand ....please help .....ima cry ffs lol
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Old 05-22-2011, 10:03 AM
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Sorry to hear about all of the problems; at this point, I would suspect the "whole new ignition and the other parts around it".

You need to ensure, that the signal to operate the starter solenoid is being sent to the starter.

I'll look up the necessary wiring, in a little while, and add it to this post.

Ok, from your description, I assume your starter is not spinning.

The crank signal circuit, is through the ignition switch (yellow wire) to the crank fuse #17 (under hood).
The wire colour changes at this point to purple.
The purple wire from the fuse goes to the PCM, telling the PCM to operate the starter relay (#47 under the hood) if the tranny is in P, or N.
The contacts of the starter relay switch power from fuse #34 to the solenoid lead (purple wire) on the starter.

Testing.

With key in the crank position, you should see 12v on fuse 17 (both sides)
Place finger on the relay, can you feel the relay operate?
If the relay operates, you should have 12v on the purple wire at the starter.
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Old 05-22-2011, 10:31 AM
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christo829 christo829 is offline
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If you replaced the ignition switch (not the keyway, but the electrical switch behind it)
it's possible that the gear isn't aligned right between the keyway and the switch. That will
allow some connections to work, but not all, and might be preventing the signal to reach
the PCM to tell the starter to go.

How bad was the damage to the original? If it was bad, you may have some damaged
wiring amongst the "whole new ignition and the other parts around it". I think RayVoy's
right about the likely location of the problem.

Good Luck!

Chris
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