[chem_man]

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.

 

[chem_man]

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!

 

[chem_man]

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..."

 

[chem_man]

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.

 

[chem_man]

If you have a youtube account, load it there and then post the link to it here.