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2004 chevy trailblazer_lt_ext
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6 Posts
Discussion Starter · #1 ·
So my 04 TB has the dreaded Service 4WD light on and no lights on the selector switch. After browsing the forums, I tried 1) removing #8 fuse, no luck. 2) went to the dealership for their diagnosis. They tell me its the EBCM and with labor going to cost $700 to replace. 3) As I generally don't trust dealers to tell me the truth, I took to a shop I do trust and had them plug in and get the trouble code. Diagnosis came back CO550- replace or reprogram TCCM which seems to be the consensus solution from the forums I've read.

My question, could their be any truth to what the dealership told me? Something wrong with both? Dealership just leading me astray? Any reason I just can't find a TCCM in the junkyard for $100 and replace it myself?

Roadie, feel free to chime in, you appear to be the expert!
 

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2002 gmc envoy_sle_xl
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I had the same symptoms after replacing the battery and bought a TCCM at a junkyard for 45.00 including tax and put it in. It took about one hour to change including going to the junkyard and removing that one. There are quite a few threads here to look at. If you remove the panel on the side of the dash facing the drivers door and look in you will see a Blue connector, a Gray connector and a smaller Black connector, they are plugged into the TCCM. If you search the treads The Roadie has a diagram showing it's location. According to what I've read here, if you pull one out of a running vehicle or at least one that was running, it does not need to be programmed at a dealer. Mine worked fine. Also they say to try to get one out of a 2003 or later.
 

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2004 gmc
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Boy, you followed the exact perfect troubleshooting flowchart. Good reading! The TCCM could perhaps have needed reprogramming to fix the wake-up issue, but the dealer declined to try that, or if they did, they thought they could sucker you in with a big fat lie.

The EBCM is no more involved in a C0550 code than a hood latch that needs lube.

$700 worth of lies. :confused: :nono: :hissy:

Borrow a buddy's TCCM if you can to confirm it, or just start looking for bargains. Best price I heard for an TCCM was $25, IIRC. Good luck!
 

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2003 chevy trailblazer_ltz
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41 Posts
GM has been known to have TCCM issues, I replaced them in both of my previous ZR2 Blazers. I am not sure if it is a Delphi or Motorola Controller but they must like to sell replacement parts....
 

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2004 chevy trailblazer_ls
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890 Posts
GM has been known to have TCCM issues, I replaced them in both of my previous ZR2 Blazers. I am not sure if it is a Delphi or Motorola Controller but they must like to sell replacement parts....
My counsin is GM of a Harley dealer and says the money is in repairs and parts not in sales - I'm sure all manufacturers have the same philosophy.
 

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2004 chevy trailblazer_lt_ext
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Discussion Starter · #7 ·
ok, here's what has been determined - at least what's been told to me by the fourth chevy dealership I've talked to. Code being returned is CO550 - TCCM REPLACE OR REPROGRAM. Cost to reprogram $65 at dealer (after other quotes of $100 and $95). Lowball dealer warns however that the encoder motor is notorious on these Chevys for acting up and cost on that part is upwards of $350. If the encoder motor was the culprit would it not also be returning a code? Should I be wary of this possibility? At $65 I have no problem going the reporgram route rather than the junkyard route and replacing myself. But now this encoder motor rears it's ugly head? Any truth to what the dealer is saying or should I swear off the dealers and just do this myself?
 

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2004 gmc
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With that code, nobody can even TALK to the TCCM to ask it if there's anything wrong with the encoder motor. And even if the encoder motor is bad you can find them on Ebay for under $200. Four bolts - one connector, you're back in business.

I advised you what to do on 12/7 and you could have had it fixed a month ago for less than the $65 reprogramming fee. And here it is January and you're still talking to dealers? :rolleyes: :hopeless :bonk:
 

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2004 chevy trailblazer_lt
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1,298 Posts
Oy.... If it was me, I'd go the junkyard route. TCCM is at least inside the cab,
so you don't have to have a decent work space to deal with. Get a post '03 TCCM,
and swap. *Then* you might be able to tell if there's really an issue with the
encoder motor. Not sure how the stealerships could tell anything about the encoder
when you can't even talk to the controller! And you know that *they* didn't do
any further diagnostics than what the computer told them!

Good Luck!

Chris
 

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2004 chevy trailblazer_lt_ext
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Discussion Starter · #10 ·
haven't been able to find a junkyard TCCM locally and Christmas is a busy time, ie no time to play monster garage on my poor TB. got a few weeks off now so I'm going to dive back in. thanks for steering me in the right direction folks.
 

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2002 gmc envoy_slt
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I think I have tried everything mentioned previously. I have a 02 envoy. Changed the actuator. Then the switch now the TCCM. I purchased all new parts. Pretty much stumped now. My service 4 wheel is a constant light. No sounds when changing switch. Light only come on when ignition first comes on. Any suggestions ??
 

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2002 gmc envoy_slt
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4 Posts
Tried most everything

Ok so I have a new actuator, new switch and a new TCCM. I dropped it to the dealer to get re flashed. They did this and nothing still worked. Only the service 4 wheel drive light. I asked them for a diagnosis. After an hour they came back with the transfer case is completely shot. There is 158K miles on this vehicle. I have only had it for about 3 months. The 4 wheel drive was working fine until about a month ago. No weird sounds or any previous problems until one day my wife switch from 4x4 to 2x4 and its now stuck in 2x4. Any suggestions would be great. I can do most mechanical myself but not sure if I want to put a new T case in this. The only thing I have not switch that I know of is the module or actuator that bolts to the T case itself?? Thanks
 
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