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2002 chevy trailblazer_lt
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Discussion Starter · #1 ·
02' TB LT 4x4, 171,000 mi.

Just replaced a broke tranny with a used one...I know not the smartest move, but save the comments. The tranny was inspected and is functioning mechanically. The issues are as follows: Speedometer now reads ZERO all the time - worked fine before swap. Tranny won't shift at all. stuck in limp mode. 4x4 selector switch now has no lights at all. I have checked the PCM harness on the tranny and all plugs are in and free of dirt, oil, shorts that I can see. I reset the computer by disconnecting the battery for 30 mins and also touching + and - leads together. Pulled Codes and they are all over the place from replace rear brake switch to replace PCM. Any ideas on where to start would be great. I feel like there is a single source of the problem, but not sure where to go at this point.:crazy::bonk:
 

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2002 chevy trailblazer_ls
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8 Posts
My best guess is short in the neut. safety switch. I say this because the 4x4 switch on the dash gets power from the pcm. so I am looking for a reason your pcm would be failing to send that power(assuming you've checked all of the relevant fuses.) Also the switch gear on the transmission shifter can be quite fragile on these. Just some places to start.
 

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2002 chevy trailblazer_lt
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Discussion Starter · #3 ·
Thanks. Would the Neut safety switch position affect this at all? Also how the hell do you remove the harness plugs from the neut switch. I know they are glued in place.
 

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2002 chevy trailblazer_ls
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I don't know how to remove the glued plugs. I have never been forced to do it.
Position seems unlikely to be the cause for all the problems you have. I myself would go back through every electrical connection carefully and follow every cable to ensure that no wires are pinched or broken and that no pins got folded over in the connectors. Once you are sure of these things, if the problems are still there I would pull it back out and return it as bad.

That's just what I would do.
 
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