02 Trailblazer 4 wheel drive problem

Paul1958

Original poster
Member
Jan 27, 2013
5
02 trailblazer having problems with 4 wheel drive hope someone can help me out. transfer case shift shaft will not move enough to change modes ,seems to indicate that's fried. I have the encoder motor and actuator hanging,actuator was extended when removed. I disassembled it to ck. internals and retracted plunger and rehung. new encoder motor and transfer case are in 2hi position when removed. service 4WD lite has been on and 4WD shift 2hi and 4hi lamps are lit even though it is set on 2hi. I tried turning key on with switch set on 2hi and actuator extended and encoder moved to 4hi position while hanging. Lites on switch did flash and acted like it was going to change to 2hi but 4hi stayed lit. Trying to figure out if this is the actuator screwing up or the TCCM. Any help appreciated!!
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
Welcome! Glad you found this site. Did you go to the old one first?

Anyway, your post is full of data, but needs a tiny bit more structure to be definitive.

How many miles, and was the transfer case fluid changed religiously every 50K? If not, and the shaft is frozen, that's a problem that has to be taken care of before worrying about the controls.

That said, 2002 TCCMs fail often in a way that all the mode lights on the switch go dark and the "Service 4WD" light on the dash turns on. Sounds like you don't have that precise set of symptoms, but I'd be curious what the state of the lights is if you pull front fuseblock fuse #8 for 30 seconds, then put it in and turn the ignition switch to RUN. No need to start the engine. What happens on the switch for lights, and how long does it take for the4 Service 4WD light to go on?
 

Paul1958

Original poster
Member
Jan 27, 2013
5
thanks for the response, I did go to the the old one first and it wasn't letting me post.The TC fluid was not changed religiously. After posting I tried hanging the old encoder with it preset to 2hi. I had dismantled it previously and nothing was broken. The new one on the other hand snapped a shaft in the spider gears when i had it hooked up not realizing the TC WAS SEIZED. When the ignition was turned on with 2hi selected the actuator retracted the lights came on the switch, I'm not sure if they flashed, then they all went out.I stopped there cause it was getting late and i could drive it in 2hi again. Going to play with the encoder some more while hanging , see what #8 fuse does for me and find a used TC.I think I can assume the actuator was screwing up because of the broken new encoder.
 

Metalbourne

Member
Jan 31, 2013
2
I also have an 2002 Trailblazer and the lights are off the switch, but no "Warning" lights are on the dash either. Does that mean it's just a bad switch if I get no warning lights? I also tried the 40 back and forth trick to clean the connecters but it didn't work.
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
Metalbourne said:
I also have an 2002 Trailblazer and the lights are off the switch, but no "Warning" lights are on the dash either. Does that mean it's just a bad switch if I get no warning lights? I also tried the 40 back and forth trick to clean the connecters but it didn't work.
Do the switch lights flash all at once when you turn on the ignition? And they stay dark later? If so, then the switch is OK and the TCCM is one of the bad ones. Even if the "Service 4WD" lamp doesn't come on in the dash. That lamp could be dead. If they never come on at the switch for the lamp test, then perhaps the TCCM has no power.
 

Metalbourne

Member
Jan 31, 2013
2
Yes, the switch doesn't light up at all. So if it's not getting power is that the fuse, switch or the TCCM that should be replaced?
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
Metalbourne said:
So if it's not getting power is that the fuse, switch or the TCCM that should be replaced?
Yes, one of those three. Check fuse #8 under the hood. Pry the switch out of the dash and make sure you have 6-12 V on the purple/white wire. That's a dimmable lamp power wire, so the lamps on the switch won't illuminate if your dash board lamps are dead for another reason (A TBC fuse in the rear fuse block) or if you have them suppressed another way. Or get at the TCCM behind the driver's left knee using the access panel on the left of the dash that's hidden when the door is closed, and check its orange wire for 12V and the black one for a good ground. Or find a buddy to swap TCCMs with.
 

gboos

Member
Jul 22, 2012
34
Btw, just one question off topic. Is it possible to change a 2003 TCCM with a 2004 TCCM without doing anything else. Just changing ?! Thanks.
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
All years, all 4WD TCCMs are interchangeable, as long as they are from a 4WD vehicle. AWD like Bravada and the other one (I forget which) can only go in AWD trucks. 2002 models are to be avoided like the plague.
 

Paul1958

Original poster
Member
Jan 27, 2013
5
Replaced the broken spider gear and encoder seams to work now, seized TC has not been replaced yet so I left encoder hanging to check mode changes and operation of actuator and encoder. Pulled #8 fuse, turned key on, service lite stayed on and with switch, actuator and encoder set to 2hi ,2hi lit up then all the lights lite then all out. Changing modes can be done with multiple tries of key on and off,sometimes mode your in lights then everything lights then all out,sometimes mode your in flashes mode you have selected flashes you can hear encoder and actuator then it goes back to mode your in. Occasionally with a successful mode change light stays lit , usually they all go out. Nothing happens changing modes with key on or with car running. Does that sound like the TCCT needs replacing ?
 

Paul1958

Original poster
Member
Jan 27, 2013
5
Started the car the next morning after having played with the encoder to figure out if the TCCT was bad and I shift into drive the car doesn't move. Tried to put it back into park it's grinding. Putting the encoder motor back on something in the transfer case must have moved and it was stuck in between modes. I had driven around for six months stuck in 2hi I guess I'm lucky this happened in the garage.This forced me to get in high gear.Got Transfer case locally from a 05 trailblazer 86k 100.00 and TCCT from 02 trailblazer 60.00. I know 02 bad "plague" and 60.00 might of been high,but it was one stop shopping and the TC price was really good. Seven hours later and we have four wheel drive just in time for the 6" to 26" of snow the're forecasting.Removing the 5 nuts that connect the TC to the transmission was extremely tedious.The Haynes manual recommends removing the frame crossbar and lowering the transmission,which looked worse to me.The top nut by the exhaust I thought was going to do me in though. I got the wrench on and moved the nut ,but could not get another position on the nut. Sliding the heat shield out of the way gave me just enough room to get another bite. Best feeling in the world was started it up and no service4WD light and it shifts into 4WD. I was also worried that I may have damaged the transmission, but that seems fine. THANKS for all the help.:wootwoot:
 

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