Hi guys, new to the forum. I too are chasing this switch light blinking , tranfer encoder motor switching by itself and from actuator noises. I'm fed up with this S%!T. I have the latest TCCM in and a new selector switch and a new front actuator. So I get in the car a the 2Hi blinking & 4Lo solid light with the selector on 2Hi. Then I put it in neutral and it shifts to 4Lo and then I reselect one at a time to 2hi. Then later it does the same thing and sticks with both lights solid. WTF. Different everytime I get in it.This my 16 year old daughter car. We bought it ne and gave it to her and now all of this crap? What to do next?
NEED HELP Problems with 4x4 not shifting
- Thread starter MIkey
- Start date
Oh, forgot to mention, hers is a 2003 LS. I apologize for my earlier post. Just really frustrated with it. I've been reading all your post for at least 3 days and been trying different things to chase down this issue. We don't need 4wd at all here either. One of my thoughts is how to disable it all together and leave it 2hi all the time. But I would rather fix it. So I've been swapping parts around from a 2005 that i found in the junk yard. I will be checking the wiring harness out today. This seems to be a cronic issue with these vehicles. I had no idea. We bought it new in 2003. Not one single problem until now (right when I gave it to my 16 yr old daughter). One thing to note is that when it goes to 4lo the gears ratio is so low and the engine sounds like its ready to blow (high rpm's). Any thoughts?
Mooseman
Moderator
Sounds like a problem with the encoder motor. Try taking it out still connected and move the selector switch to observe what happens. If it moves and selector lights work as they should, no flashing, then it's fine and possibly your transfer case has issues. If it doesn't move and /or the lights flash or don't go where they're supposed to, this would point to the encoder motor.
gmcman
Member
- Dec 12, 2011
- 4,656
Have you been changing the TC fluid at the 50K interval?. I'm sure there's a grace period but mainly has it ever been changed?
My last 4WD issue was with a brand new axle shift actuator on the front disconnect. In the 2HI position, the plunger was fully extended. If you remove the actuator and are able to push the plunger in with the selector in 2HI, then that's likely the issue.
FYI, you cannot select 4LO unless the trans is in neutral, not even in park, must be in neutral.
My last 4WD issue was with a brand new axle shift actuator on the front disconnect. In the 2HI position, the plunger was fully extended. If you remove the actuator and are able to push the plunger in with the selector in 2HI, then that's likely the issue.
FYI, you cannot select 4LO unless the trans is in neutral, not even in park, must be in neutral.
Thanks guy's for the tips. I did do the transfer case but at ~75k i believ. Will do it asap. We traded Grandpap the TB in 2012 for his 2007 Tahoe LTZ since our family was growing. Then my oldest turned 16 and we got it back for her. I see no entries in the maintenance log since my last when it was @ 88k So, I will take your advice on it. Secondly I will do the encoder motor as well. I did get anther encoder motor from a 2005 from the junk yard. May open it up and check the encoder ring like I saw someone do earlier in another post. She drove it today twice and the light stayed solid in 2hi. I really appreciate the input. Will get back to you.
So, what you're saying is that if I have the selector switch in 2Hi and pull off the front disconnect and then with my finger are able to push the plunger in, then my problem is with the front disconnect? I just put a new one on that I got from Amazon. Not oem. So what I did do is go to GM PartsGiant.com and put my VIN in and decided to order the OEM. I do have the current OEM TCCM in tho. I also ordered another selector switch. I opened up the encoder motor that I got from an '05 and checked the ecncoder ring. It looks great. No cracks or corrosion. May swap it out when I do the TC fluid What is the current recommended fluid? Thanks
Another question if I may. I put the '05 TCCM on the '03 TB. Do I need to get it flashed?
GM Part No.: 12590220
GM Part No.: 12590220
gmcman
Member
- Dec 12, 2011
- 4,656
I bought a brand new disconnect on Amazon from GWA. The first time I tried driving in 4 HI it worked as it should.
When I placed it back in 2HI is when the plunger stayed in the extended position.
This is the pic I sent them. Plunger is extended when it should be more recessed.
When I placed it back in 2HI is when the plunger stayed in the extended position.
This is the pic I sent them. Plunger is extended when it should be more recessed.
Mooseman
Moderator
No. All the same programming. All '02 and some early '03 had TCCM's that would fail.
I wonder if that cheap-o I got from Amazon is part of the problem? When I go to put the OEM in, I'll check the position and plunger. I hope it not broke inside the TC. Thanx again!
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Thanx. Didn't want to go to the dealer on that TCCM anyway. So it's staying in for now.
Update. So, I received the OEM selector switch (made in Taiwan?) and the new AC delco front diconnect actuator. I also checked the spring loaded "fork" on the disconnect. It was good so I installed them and everything functioned normally. Then 2 days later the 2hi started blinking. So we proceeded to put it in gear as normal, drove off and it went solid. I will be doing the transfer case fluid this weekend.
So. there was no light on 2hi then she put it in neutral and then 2hi light went solid and it was ok.
That is curious! I suspect a worn encoder ring sensor. That's the part insode the encoder motor that reports where the transfer case shift motor is positioned. That sensor circuit goes live as soon as you open the door, even before the key is in the ignition!
I do have another encoder motor that I got from a 2005 TB. I opened it up and checked the encoder ring on it. It looked new. So I will change it out when I do the transfer case fluid change.
On a very slight incline. Basically a normal driveway incline. But not steep or anything.
If it the open type this is the kind of degradation to look for, particularly at the 2Hi position.... If it is the closed type you will not be able to see anything useful.
I went through this hoopla a while ago. Uncommanded switching to 4high and the last straw was also self switching to 4lo - quite a shock when it happens at 35mph.
Here's what I did that appears to have solved the problem:
I removed the encoder motor and checked the encoder ring for continuity. I also checked that the motor spins and didn't make any unusual noises. I also lubed the gearcase. After reinstalling the lights went haywire and service 4wd was on.
So I removed the encoder motor again and found no continuity in the encoder ring
Time for shopping at the PYP.
I picked up a 05 tccm and encoder ring. Installed them both in my 02.
It's been a few months and the problem has not returned. I still hesitate to say the issue is solved since the shifting happened randomly every few months. But it seems promising.
Some key points to note:
I removed both a 02 and 05 encoder ring. The 02 could be installed as is, but the 05 newer style ring had a high impedance oxide coating on the terminals that I had to sand off. I would suggest coating the terminals with dielectric grease to prevent the oxidation causing future problems.
And the 02-03 tccm is known to have issues, so while you're in the yard you might as well get one of those from an 05+ truck too and eliminate that from the potential cause of the problem.
Good luck!
Here's what I did that appears to have solved the problem:
I removed the encoder motor and checked the encoder ring for continuity. I also checked that the motor spins and didn't make any unusual noises. I also lubed the gearcase. After reinstalling the lights went haywire and service 4wd was on.
So I removed the encoder motor again and found no continuity in the encoder ring
Time for shopping at the PYP.
I picked up a 05 tccm and encoder ring. Installed them both in my 02.
It's been a few months and the problem has not returned. I still hesitate to say the issue is solved since the shifting happened randomly every few months. But it seems promising.
Some key points to note:
I removed both a 02 and 05 encoder ring. The 02 could be installed as is, but the 05 newer style ring had a high impedance oxide coating on the terminals that I had to sand off. I would suggest coating the terminals with dielectric grease to prevent the oxidation causing future problems.
And the 02-03 tccm is known to have issues, so while you're in the yard you might as well get one of those from an 05+ truck too and eliminate that from the potential cause of the problem.
Good luck!
Thanks for the info. I did pull a TCCM from an '05 and installed it. I also ordered and installed an OEM selector switch & front disconnect actuator. While it was out, I checked to see if I still had a spring load on the "fork" that engages/disengages the front axle. It checked good. So, this weekend I'll change the transfer case fluid and install the encoder motor I got from the same '05. I looked at the encoder ring and it seemed to be OK. It kinda looked new. Thanks guy'sI went through this hoopla a while ago. Uncommanded switching to 4high and the last straw was also self switching to 4lo - quite a shock when it happens at 35mph.
Here's what I did that appears to have solved the problem:
I removed the encoder motor and checked the encoder ring for continuity. I also checked that the motor spins and didn't make any unusual noises. I also lubed the gearcase. After reinstalling the lights went haywire and service 4wd was on.
So I removed the encoder motor again and found no continuity in the encoder ring
Time for shopping at the PYP.
I picked up a 05 tccm and encoder ring. Installed them both in my 02.
It's been a few months and the problem has not returned. I still hesitate to say the issue is solved since the shifting happened randomly every few months. But it seems promising.
Some key points to note:
I removed both a 02 and 05 encoder ring. The 02 could be installed as is, but the 05 newer style ring had a high impedance oxide coating on the terminals that I had to sand off. I would suggest coating the terminals with dielectric grease to prevent the oxidation causing future problems.
And the 02-03 tccm is known to have issues, so while you're in the yard you might as well get one of those from an 05+ truck too and eliminate that from the potential cause of the problem.
Good luck!
Welp. The TB went in to 4lo and got stuck with a service 4wd light. So I decided to put the '05 encoder motor in. When I got under there, i went to disconnect the plug and it just felt like it was barely connected. I also noticed the plug was not secured to the little bracket. When I pull the encoder off, I also found it to be a Doorman replacement. Grand Pap must have had it changed. So I put to'05 encoder on anyway and secured it to the bracket and tie wrapped to plug so it cannot get disconnected.
Fired up the TB and went through all the settings on the selector switch and it worked flawlessly. So I'm leaning toward a loose connection partially because it was not secured properly and being banged around possibly causing the connector to loosen up. Next is the transfer case fluid change.
Fired up the TB and went through all the settings on the selector switch and it worked flawlessly. So I'm leaning toward a loose connection partially because it was not secured properly and being banged around possibly causing the connector to loosen up. Next is the transfer case fluid change.
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Update fellas! Changed out the encoder and changed transfer case fluid and all is good so far. I believe the loose connector flopping around was the problem. Thanks for all the help guy's. Good to know people still driving them and sticking around on the forum to help a fellow TB owner out. Hats off to you all.
Mike
Mike
