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2004 chevy trailblazer_lt
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What year is the TrailBlazer, and have you scanned for codes using a code reader/live data scanner that will show body and communication codes?

I can only postulate at what occurs. I cannot tell you why your trailblazer goes from D to N to R to P. Does it actually shift or is the vehicle still in Drive but the Instrument Panel Display showing the changing of the gears?

When the Body Control Module is told the transmission has shifted into Park, it sends a command to the door lock actuators to go into the unlock position. This is what I am figuring is happening.
 

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Discussion Starter · #3 ·
Yes I have used a good scanner a snap-on one.my farther in law works at a transmission shop and he can't figure out why it does it. The scanner said something about my cluster. When im driving it will go in to neutral but not par or reverse the cluster just shows it going through all the gears many times.
 

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Discussion Starter · #4 ·
What year is the TrailBlazer, and have you scanned for codes using a code reader/live data scanner that will show body and communication codes?

I can only postulate at what occurs. I cannot tell you why your trailblazer goes from D to N to R to P. Does it actually shift or is the vehicle still in Drive but the Instrument Panel Display showing the changing of the gears?

When the Body Control Module is told the transmission has shifted into Park, it sends a command to the door lock actuators to go into the unlock position. This is what I am figuring is happening.
[/QUOT
So when im driving my 5.3 trailblazer it will go from d to n to r to p back to drive. it unlocks my door. Why does it do this I don't have no codes for it.
2006 5.3 ext trailblazer ls
 

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2004 chevy trailblazer_lt
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OK, thanks. If you can, get him to re-read the codes, and write them down for us.

Instrument Cluster problems/gremlins are not unheard of - typically either a bad solder joint or a bad stepper motor. If you are any good at soldering you can remove the IP cluster and look at it with a magnifying glass. You will be looking for dull grey areas of solder (a cold solder joint) as opposed to a normal joint which will look nice and shiny and silver. Using a 15 to 30 watt or so soldering iron, you can reheat the cold solder joints, let the solder melt and reflow (maybe add a tiny bit of new solder) and then let it cool and it will be good as new.

Now if your transmission is actually dropping out of drive and going into neutral while driving, then I would first look at the Park Neutral Safety Switch (or Neutral Safety Switch) to make sure it is secure and that the wiring to it is secure and has not been munched on by rodents.

Also, I am going to ask one of our resident transmission specialists (Ravalli Surfer) to chime in and review this as well.

Good Luck!
 

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'05 Chevy TB EXT
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Hello! I'm in the shower right now, and I'm sorry I missed your call.

Your call is important to me and I will return your call in the next 30 minutes.
 

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2004 chevy trailblazer_lt
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Hey, I just saw you in another thread. At least you could have come up with a better excuse like "... please let me read the earlier posts, mull it over while I down some hooch, and then I'll get back to you..."
 

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Discussion Starter · #8 ·
Ok thanks my father thought it was that neutral switch at first. but the scan tool said it was good. it said a bad body control module then and now it says my body control module is good now. Yes it drops in to neutral while driving my truck will Rev and the mph needle will drop to o mph. And I will get the codes again I plan on just getting a new cluster.
 

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2004 chevy trailblazer_lt
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OK. I would wait until Ravalli gets out of the shower for his take on things. It sounds like it could be something electrical - perhaps a loose connection, a flaky ground, etc.
 

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'05 Chevy TB EXT
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Let me get this straight ....

1. You said: "it drops in to neutral while driving my truck will Rev and the mph needle will drop to o mph. " . and does this mean that the vehicle is actually stopped when the speedo gets to zero?

2. You said: "it will go from d to n to r to p back to drive " .... and does the transmission ACTUALLY feel like it does all that shifting gymnastics?

IOW ----> does it try to go into PARK whilst it is moving FORWARD ... or is the quadrant indicator in the nacelle reporting this anomaly?​
What kind of noise do you hear when it tries to go into PARK while in motion .... this is a very important quest3ion and requires a very accurate answer.​

At the moment, we'll ignore the door-lock/unlock thingy for the nonce.

If the truth be told -- I was watching a Charles Bronson movie and I had it on PAUSE while I was in the shower .... no alcohol was involved ....
 

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Discussion Starter · #11 ·
I will be driving 70mph then my truck shift to neutral by its self.while the shifter still in drive spot. It does in gage neutral then it goes back to drive. When in neutral the mph needle go to 0 mph while I'm driving 70mph. It doesn't make no sound while doing it.
 

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Discussion Starter · #14 ·
OK. I would wait until Ravalli gets out of the shower for his take on things. It sounds like it could be something electrical - perhaps a loose connection, a flaky ground, etc.

I've checked my grounds and the connectors on the transmission. they where good and dry on the inside. we thought they might have got wet somehow.
 

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'05 Chevy TB EXT
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I've checked my grounds and the connectors on the transmission. they where good and dry on the inside. we thought they might have got wet somehow.
STOP ---- you're hearing zebras when it's really horses.

Quit panicking and let's work this LOGIC TREE correctly --- branch by branch ---> and don't chop the whole thing down.
 
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