4x4 Not Working

andy702252

Original poster
Member
Dec 22, 2011
76
It has been a while since I worried with this problem, but snow will be upon us soon. My 4x4 hasn't worked for sometime, before the lights on the switch would not even light up, I replaced the tccm and the lights are back on but it know has the "service 4x4". The selector light is on but it only stays on 2HI, if I put it somewhere else like on 4hi or 4lo the light just blinks.
 

Robbabob

Member
Dec 10, 2012
1,096
Do you hear the TC trying to move? Make sure all the connectors are seated and there aren't any wires worn through or shorted.

By the time you might reply with this information, others will chime in to give a more direct line to resolve. This is a decent starting point.

Good luck!
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
Listen for the TWO noises that happen underneath. The front axle actuator is a high pitched whine that happens for just over a second, and ONLY on 2WD->A4WD transitions and vice versa. The transfer case encoder motor is a lower pitched (larger motor) noise that happens for a shorter time during EVERY mode transition. I should really get a recording of this.

Could you try each of the transitions (don't jump two at a time), and describe the motor noises and the mode switch light behavior very precisely? Thx.

The way the two motors work is that the TCCM commands them to a new position, and they have position feedback sensors that report back the success or failure of the command. The blinking light on the mode switch is the report of failure back to you. But troubleshooting it involves listening carefully to the noises, but you can do this with the ignition in RUN but the engine off to make it easier. I recommend EVERYBODY do this while their 4WD system is working to get a memory of the noises. Sometimes you can diagnose a failure by sound alone.

Are you going to get down there and want to get a voltmeter on the harnesses and DIY? Or pay a mechanic with a lift to fix it? What's the ultimate goal of the troubleshooting process here?
 

Robbabob

Member
Dec 10, 2012
1,096
the roadie said:
I recommend EVERYBODY do this while their 4WD system is working to get a memory of the noises. Sometimes you can diagnose a failure by sound alone.

Totally agree. Might should be a routine check once a month, in your driveway or parking stall. Engine off, key in run, lever in neutral. Perform the actions and listen to the movements. If you're not familiar with what it should be, then you'll never know when it's gone bad.

It's just called, being prepared. And this prep costs nothing!
 

andy702252

Original poster
Member
Dec 22, 2011
76
Okay heres the update, so far I have replaced the selector switch, actuator, and tccm. The first noise the actuator is working correctly.
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
So you get no noise from the transfer case encoder motor that should activate in EACH mode transition? Check the connector at the encoder. Consider replacing the assembly.

I don't recall advising to change the switch or the actuator, but maybe you just shortened your full report of what you observed.
 

andy702252

Original poster
Member
Dec 22, 2011
76
Yea I just took the initiative to do those to eliminate potential problems, plus I work at a parts house so the prices aren't that bad. I have purchased the motor, just hope that fixes the problem if not, Im lost.
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
andy702252 said:
...just hope that fixes the problem if not, Im lost.
Not really. You just have to do some guided troubleshooting and understand how the systems work instead of throwing parts at the problem and hoping. TPATPAH is ultimately unsatisfying even if it intermittently works.
 

shadiBLebz

Member
Apr 19, 2012
52
My switch lights for my 4x4 stoped turning on as well (orange lights) . Was working fine. Is this because of the tccm. .
Sorry to butt in
 

Robbabob

Member
Dec 10, 2012
1,096
shadiBLebz said:
My switch lights for my 4x4 stoped turning on as well (orange lights) . Was working fine. Is this because of the tccm. .
Sorry to butt in

The mods will move as they see fit.

To be clear, you rotate the switch and nothing happens?
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
You have a 2002. 97% chance you need a redesigned 2003+ TCCM. Amazed it lasted this long. Extensively discussed if you need the part numbers. Get a used one from junkyards or Ebay to save $ and a dealer visit for reprogramming a virgin one.
 

shadiBLebz

Member
Apr 19, 2012
52
the roadie said:
You have a 2002. 97% chance you need a redesigned 2003+ TCCM. Amazed it lasted this long. Extensively discussed if you need the part numbers. Get a used one from junkyards or Ebay to save $ and a dealer visit for reprogramming a virgin one.

I shall have a look at the moment the 4x4 just re-engaged it self it has had a habit of doing so of recently due to the cold weather I'm assuming.

But I will call a few junk yards in my area and check it out. You did say that a 2003 would be compatable with my 2002?
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
Every year TCCM will work to replace a bad 2002. As long as it's from a true selectable 4WD vehicle with a low range transfer case like the TB and Envoy. Just don't get a TCCM from a Bravada or other AWD variant. Those will cost you another $100-150 for a dealer reprogramming visit.
 

Matt

Member
Dec 2, 2011
4,009
the roadie said:
You have a 2002. 97% chance you need a redesigned 2003+ TCCM. Amazed it lasted this long. Extensively discussed if you need the part numbers. Get a used one from junkyards or Ebay to save $ and a dealer visit for reprogramming a virgin one.

Mine is still going strong...I'm amazed myself!
 

Sparky

Member
Dec 4, 2011
12,927
Matt said:
Mine is still going strong...I'm amazed myself!

Careful, I said that about mine and it croaked a month later :wink:

Also maybe yours was replaced already before you got the truck? Unless you're the original owner, then never mind that.
 

Matt

Member
Dec 2, 2011
4,009
Sparky said:
Careful, I said that about mine and it croaked a month later :wink:

Also maybe yours was replaced already before you got the truck? Unless you're the original owner, then never mind that.

Second owner. And, to be honest, I believe the original owner was a sheila, so I doubt it's been changed. I know it's going to go because about 9 or so months ago, it's put itself into low4 when I was going to back into the garage...hasn't done it since.

Probably should get one for a spare WHEN it goes.:undecided:
 

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