Help with 4x4 - Service 4x4 light and selector lights on sometimes

Gerbil21

Original poster
Member
May 28, 2014
839
Hi this is my first post and unfortunately it has to be one with a problem

so here's the problem i recently bought a 05 gmc envoy with 138k the service 4x4 light was on before we bought it and the guy said it was because of the remote start that was recently installed and i never checked to see if it worked so now that i have had time to fully look at it i noticed a few things

1.service 4x4 light is on almost all the time but sometimes it goes off but comes back pretty quick

2.there are usually no lights on the selector switch but sometimes they go on when the 4x4 light goes off and sometimes its on when the 4x4 light is on

3.i scanned the codes and got u1026 it was a code for no communication with tccm

4. when selector switch light is on and i turn knob nothing happens

so i have no idea where to go with this info

but one thing i can say is that most of the times the light goes off (or on) is when hitting a bump but some times it does the same on smooth roads

this leads me to the other day when i hit a pretty big bump while stopping i noticed the 4x4 light went off and the selector lights went on
when i got home i turned the switch from 2hi to a4wd and it flashed over it but no sounds then i turned it to 4hi and the same so i went back to 2hi and it stood there

i have tried pulling the fuse which usually gets the selector switch on but still nothing

any help is appreciated


also i have rear air suspension that sags mainly to the passenger side and sometimes would deflate completely but while driving stays leveled but still sagged a bit to the passenger side also i have been next to it when it deflates and you can hear it deflating (it sounds like a leak in a tire) would this be bad bags or someting else? since sometimes it stays leveled overnight
 

Hatchet

Member
Nov 21, 2011
2,405
If you only getting the one U code, chances are its a bad TCCM. But you can always check the ground for the data pack. Its located on the passenger side left foot well under the center counsel.

I can't seem to find the diagram with the ground location.
 

Gerbil21

Original poster
Member
May 28, 2014
839
Hatchet said:
If you only getting the one U code, chances are its a bad TCCM. But you can always check the ground for the data pack. Its located on the passenger side left foot well under the center counsel.

I can't seem to find the diagram with the ground location.
i will check for codes again today when the ligtht is on and when its off also i just downloaded the fsm from here so i will see if its in there

Thank you for the help
 

Hatchet

Member
Nov 21, 2011
2,405
Found it.
 

Attachments

  • img026.jpg
    img026.jpg
    165.9 KB · Views: 30

Gerbil21

Original poster
Member
May 28, 2014
839
Hatchet said:
Found it.
Thanks for finding it for me but I won't be able to check since its pouring but will I have to remove center counsel?
 

freddyboy61

Member
Dec 4, 2011
276
Before tearing the center console apart to get to the ground pack, check the connectors at the TCCM. Since the previous owner said the problem started after a remote starter was installed, I would suspect something under the dash was knocked loose or disturbed.
 

Hatchet

Member
Nov 21, 2011
2,405
Gerbil21 said:
Thanks for finding it for me but I won't be able to check since its pouring but will I have to remove center counsel?
no. From the passenger side of the counsol. there is a little carpet piece held in with a screw. Remove that screw and you will see it. It looks like an electrical connector bolted to the body.
 

Gerbil21

Original poster
Member
May 28, 2014
839
freddyboy61 said:
Before tearing the center console apart to get to the ground pack, check the connectors at the TCCM. Since the previous owner said the problem started after a remote starter was installed, I would suspect something under the dash was knocked loose or disturbed.
Is there anything specific to look for?

Hatchet said:
no. From the passenger side of the counsol. there is a little carpet piece held in with a screw. Remove that screw and you will see it. It looks like an electrical connector bolted to the body.
I have plastic on the sides of my counsel
 

Attachments

  • IMG_20140605_161700.jpg
    IMG_20140605_161700.jpg
    91.3 KB · Views: 25

Hatchet

Member
Nov 21, 2011
2,405
This area
 

Attachments

  • post-12279-0-28061700-1401999519.jpg
    post-12279-0-28061700-1401999519.jpg
    94.2 KB · Views: 20

Gerbil21

Original poster
Member
May 28, 2014
839
Hatchet said:
This area
So I guess I'm still going to have to take out the counsel but it's OK I was going to do the xm aux input mod soon either way


Thanks for highlighting it lol I found it I will check once I get home. Thanks again
 

IllogicTC

Member
Dec 30, 2013
3,452
Gerbil21 said:
So I guess I'm still going to have to take out the counsel but it's OK I was going to do the xm aux input mod soon either way


Thanks for highlighting it lol I found it I will check once I get home. Thanks again
That part of the carpet is actually carpet run over a plastic shroud (there's some official name for it I can't think of). Should be a screw on the passenger side and a screw on the driver side. May be able to fidget it out or bend it just enough to do your thing without breaking it.
 

Hatchet

Member
Nov 21, 2011
2,405
IllogicTC said:
That part of the carpet is actually carpet run over a plastic shroud (there's some official name for it I can't think of). Should be a screw on the passenger side and a screw on the driver side. May be able to fidget it out or bend it just enough to do your thing without breaking it.
That's what I did. Pulled it back and up enough for me to get a grip on the bolt.
 

Gerbil21

Original poster
Member
May 28, 2014
839
ok i know that i am now posting again a month later but i figured the problem out (kinda) - when i first checked the tccm i looked at the wires only and they were all in and seemed fine

yesterday i pulled the box out from behind all the remote start wires and realized my problem, the black 4 pin connector was able to slide in and out since the plastic around it was cracked on the edges so i crazy glued it and now it holds good and the selector switch lights stayed on after a long bumpy drive and the transfer case engages and moved through all positions but the front dose not connect since the light stays flashing on the selector and there is no noise so if anyone can tell me which wires are which in the actuator connector that would be great.

i know that the connector is supposed to have +12v, ground, and a feedback and input to and from tccm but which is which?

there is a video on youtube (not mines) that has the same problem
https://www.youtube.com/watch?v=LmceKaB-2g0
 

Gerbil21

Original poster
Member
May 28, 2014
839
Anyone got any ideas?
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
The wire diagrams are all in Mooseman's manuals, available for download in a Pinned (sticky) thread. Or in the TCCM system schematics I've posted many times. Recommend a Google search like this: "tccm schematics site:gmtnation.com" and then to get right to the schematics, hit the "Images" button on the Google results list.
 

Gerbil21

Original poster
Member
May 28, 2014
839
The_Roadie said:
The wire diagrams are all in Mooseman's manuals, available for download in a Pinned (sticky) thread. Or in the TCCM system schematics I've posted many times. Recommend a Google search like this: "tccm schematics site:"gmtnation.com" and then to get right to the schematics, hit the "Images" button on the Google results list.
OK I got it, the 05 FSM didn't want to download on my tablet but I found the diagrams on bbbind
Now if I'm able to check the wiring on the front actuator what should I see?

This is what the diagram says
Black- ground
Lt. Blue- Actuator Control
Brown- 12v
Black./wht.- Axle switch signal

So which wire would have the tccm high and
Low signal to make them motor move? And which would be the return line to the tccm? I'm guessing actuator control (Lt. Blue) is from the tccm right?

What should i see if I check blue and black/white and what are the values of the high and low command
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
The control line IIRC is 5V or ground to make the motor spin one way or the other, and when it's left floating it goes to 2.5V and then the motor doesn't move. I may be wrong on the voltages, though. But I know that if it floats, the motor doesn't move.

The switch signal changes state when the actuator fully extends. See my definitive theory of operation thread here:
http://forums.trailvoy.com/showthread.php?t=46356
 

Gerbil21

Original poster
Member
May 28, 2014
839
Ok I know this update is really late but I've been busy with my 8mpg

So far the 4wd switch lights have been on since my last post, and the service 4wd light has not come on.

Yesterday I tried to switch it to 4wd and the t. case made noise but no noise from the front disconnect but this time the service 4wd light came on and set one code c0306
IIRC it's for motor A or B circuit after clearing the code it came back with a ign. cycle but this morning it hasn't came on yet.

I will check what roadie said this Sunday on the front actuator

Any ideas on the code?
 

IllogicTC

Member
Dec 30, 2013
3,452
Gerbil21 said:
...C0306...

Any ideas on the code?
DTC C0306
Circuit Description
The transfer case motor is a bi-directional, permanent magnet, DC motor. When energized through motor control A or motor control B, the ground is provided by the opposing motor control circuit and then grounded through the transfer case shift control module ground circuit. The motor, through a series of gears, rotates a shaft, which moves the mode and range forks to shift the transfer case between the following ranges:
  • 2HI
  • 4H
  • 4LO
  • AUTO 4WD
  • Neutral
This DTC detects an open, short to voltage or short to ground in the motor control A or motor control B circuits or an open or short to ground inside the motor.

DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC C0306 Motor A or B Circuit Malfunction

Conditions for Running the DTC
  • The ignition is ON.
  • System voltage is 9 - 18 volts .
Conditions for Setting the DTC
  • The system tests the motor circuits by checking for unwanted voltage.
  • Then, the system supplies voltage on each of the motor circuits and reads the voltage back on the other circuit.
  • If the system detects a condition with the circuits, the DTC is logged. The transfer case shift control module senses a low voltage return in the motor control A or motor control B circuits when a high voltage is expected.
  • The fault must remain current for 30 seconds to set the DTC.
Action Taken When the DTC Sets
  • All shifting is disabled.
  • The SERVICE 4WD indicator remains illuminated for the remainder of the current ignition cycle.
  • The transfer case shift control module provides a reference voltage of 4.5 volts on the motor A/B line for diagnostic purposes.
Conditions for Clearing the DTC
  • The transfer case shift control module clears the DTC if the condition for setting the DTC is not currently present.
  • A history DTC clears after 100 consecutive ignition cycles without a fault present.
  • History DTCs can be cleared using a scan tool.

2nhnhah.png
 

Gerbil21

Original poster
Member
May 28, 2014
839
Any idea where these connectors & grounds are?
 

Gerbil21

Original poster
Member
May 28, 2014
839
The_Roadie said:
The encoder motor is on the transfer case, but the wiring goes back to the TCCM. Using the schematics, you can check these at either end, whatever's more convenient.
do you know Which connector is it and what are the wire colors?
 

Gerbil21

Original poster
Member
May 28, 2014
839

Gerbil21

Original poster
Member
May 28, 2014
839
Ok what should I be seeing on the wires and which ones would I test against
 

Gerbil21

Original poster
Member
May 28, 2014
839
Ok so the front actuator gets 10v then after a shift it goes to 0v, going back to 2w and back to 4w it stays at 10v

Also it dosent shift to 4lo and there is power on the 4lo signal wires

I can see the voltage changes when.checking both motor wires it ranges from 5v up to 10v
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
Gerbil21 said:
Ok so the front actuator gets 10v then after a shift it goes to 0v, going back to 2w and back to 4w it stays at 10v

Also it dosent shift to 4lo and there is power on the 4lo signal wires

I can see the voltage changes when.checking both motor wires it ranges from 5v up to 10v
Not enough detail to help. WHICH specific wire on the front actuator are you measuring? Is the schematic clear on the function of each of the wires or should I share my little theory of operation paragraph?

What do you mean by "both motor wires" and on which connector are we discussing in your third sentence?

Are you in NEUTRAL, not park or drive, when you try to go into 4LO? And what do you mean by the "4LO signal wires"?
 

Gerbil21

Original poster
Member
May 28, 2014
839
I tested the c1 ( 16 pin black plug) Actuator control- lite blue wire on the tccm side and got 10v but after a shift to 4wd it goes to zero then when I goto ->2wd and back to ->4wd it stays at 10v which is because of what you said (the actuator gives up after a failed attempt to operate the disconnect fork)

I am referring to motor control A & B wires ( Black 4 pin connector, wire colors black & red)

Also I just realized I was in park the whole time so that's why 4lo didn't work

One other thing I've noticed is on another thread someone you talked to their problem was the wires from the actuator to the tccm was crushed and got no response from the actuator. I noticed on the wires he talked about had no power for me either.

Since I don't hear the actuator then maybe its not getting power? I would test it later if I can
 

Gerbil21

Original poster
Member
May 28, 2014
839
OK just a little update yesterday I took out the actuator and noticed the grease was brown and looked like peanut butter so I removed the whole disconnect and re greased it.

All of the parts looked great and did not have any signs of wear, I then opened the actuator itself and it looked good inside so I cleaned it with some electronic spray and put a tiny bit of grease on the plastic gears. After I reassembled everything I plugged in the actuator and switched to 4hi and It slightly moved but not much and the selector switch kept flashing, so I disassembled it again and realized while looking at the roadies thread of the operation of the actuator that the actuator was all the way in instead of being out like it is supposed to be (you can see In his pictures what I mean the part that sticks out of the actuator needs to be all the was out which you can Turn by moving the wheels Inside the actuator)

So I reset the actuator and tried again switching to a4wd, 4hi, and 4lo and everything worked I then put the actuator in the disconnect and everything worked perfect as well (this all happened with the passenger wheel off the ground) so after we reassembled the whole suspension my dad moves the car back and I picked up the tools but when I went to see the 4wd finally working it kept flashing and a code c0379 came up so now I'm lost how can I work perfect then not work

Also from what I've seen every part of the 4wd system is stock and was never changed the are all OEM from 2005
 

Gerbil21

Original poster
Member
May 28, 2014
839
ok so i took out the actuator again and it was retracted all the way in so i turned the wheels inside the actuator and had it sticking all the way out (i also found out when you do this you will get to the end and then you have to go back so there is free play both ways in the wheels)

after i got the actuator sticking out 4x4 worked and the lights were solid but i did notice that it never went back in (the actuator) when going from 4wd to 2wd the actuator never moved so i put it into the disconnect and tried 4wd again and it worked. so i put the wheel down and it still worked then i moved the car back and forth and then once again it didn't work. so idk why but it seems that once i move the car it dosent work.

one other thing i noticed is that when the actuator was in the disconnect and i was in 4wd while there was resistance on the wheel it had the same amount of resistance when in 2wd.

so im guessing that the whole system is good and i just have to replace the actuator, right?
 

Gerbil21

Original poster
Member
May 28, 2014
839
One other thing I noticed today was the posistion of the actuator, Is it supposed to be all the way out when installing because all the pics of new parts show it slightly in rather than all the way out. Or do I put it all the way in?
 

Gerbil21

Original poster
Member
May 28, 2014
839
ok well i ordered a new actuator after i kept testing the old one and after it finally quit working

during the test i noticed it would either bind up, not work, or spin it self inwards (2wd) and bind up

i also tried just plugging the board in and pressing the fingers onto the board by hand and when i did it would click but the motor never moved but i did notice the 4wd light stood steady so i guess i will have to wait and see if the new actuator fixes everything. this seems to be the one part that has failed in the whole system (all parts are oem)

also i never knew the car will go crazy with a dead battery lol after i finished i went to move it closer to the curb but the batt was barley alive the gauges would dim when i turned it to the on pos. and the headlight washers sprayed, also it showed service brake system, and the xm didnt work lol :biggrin: but now it seems better lmao :rotfl:
 

IllogicTC

Member
Dec 30, 2013
3,452
A new actuator definitely seems to be the best choice. It's nice to see that you at least tried to diagnose and resolve the issue before shooting out some perfectly-good money for a new one. It's one of the things we strive for around here; teaching to diagnose and fix without always just buying a new part. I mean it's a viable strategy and up to the car owner of course, but we like saving money!
 
  • Like
Reactions: Gerbil21

Gerbil21

Original poster
Member
May 28, 2014
839
yea well hopefully this fixes it, it should be coming in on the 26th after i get the new one in i will post some pics of dissembling the old one so if someone finds this thread they know how to do it. also i will force power the motor on and see if it really is truly dead :undecided:
 

Gerbil21

Original poster
Member
May 28, 2014
839
OK well the actuator solved my problem and 4x4 is working perfect![emoji1]

So to summarize everything for someone else who reads this thread

1. Search the forums

2. Check what you can
2a.check for 4wd lights on the dash
2b. Check for selector switch lights
2c. Check for the two noises when shifting to 4wd the transfer case noise is super obvious but the front actuator is a little harder just have someone else listen or have the pass door open.

3. Check wiring
3a. Tccm wiring is the first to Check (3 plugs, the 4 pin main power supply for the tccm was the fault for me, the clip was broken and the plug would slide off but that nothing crazy glue can't fix)
3b. Check voltages ( search for tccm schematics and test for the voltages on the corresponding wires, check the 4 pin first)
3c. Check for signals ( check to see if the Signal to and from the tccm ever gets received)

4.check for codes ( get a good code reader that can read specific codes, I use car gauge pro and I can read transfer case codes)
4a. If you get a u1026 that is because there is no communication between two modules so something is not plugged in or is cut/crushed
4b.if you get c0379 it is for the front actuator (I only got this code at its last dying days)
4c. Dont fully trust the codes during the time I fixed the tccm and now the 4wd light will stay off but one time that I shifted it the light came back up and it showed a code for c0306 which is for the encoder motor. After I reset the code it came back but eventually went away after a ignition cycle.

5.check the parts
5a. All of my parts are original OEM except the front actuator now, but you should check the build dates on the parts, if you have a 02 just go ahead and replace the tccm that is most likely your problem. If not then see of the dates match with your vehicles build date if there off by a year or so then most likely its been replaced which can be a good thing but can also be bad since you still have problem a dont know what they were diagnosing.
5b.check the fuses, the are two fuses one in the rear labeled 4wd (15A) and one in the underhood fuse box labeled atc (10A?) pulling this fuse while the ignition is on for a minute or so usually resets the tccm and when I wakes up it may show codes or work

6.listen
6a. The Transfer case makes a loud distinct sound and is right under the driver seat.
6b. The front disconnect actuator makes a motor spinning/whirling sound kind of like those toy cars that you pull back and they speed away when you release
it

7. The best thing you can do is check, if you think something is wrong, you don't have to get your hands dirty checking the tccm but the front actuator you will need some gloves and tools (8mm socket and a long extension and you can replace it with the wheel on and the car and on the ground.

One othen main thing to keep up on is service you have to change transfer case fluid every 50k and differential fluid every 100k

also whenever you do service on the passenger side suspension and you take off the axle or remove the strut you should take off the front disconnect aswell (8 bolts all 15mm) and re grease it. you should use a high temperature, water resistant grease. If there's wear on the parts you should use a grease that is has moly in it.
 
Nov 20, 2018
4
Ludington
Very helpful thread! Real quick though.... I'm working on the wife's 2007 Saab 9-7x 5.3i. It's AWD and I have no idea where the TCCM is to check the signals at the wires. AWD light comes on with ignition. Sometimes it doesn't, and the AWD seems to work well.... but it always comes on eventually. Showing code C0306 which is that Circuit A/B issue. Clears and comes right back most of the time. Solid center console, so I'll likely have to pull it for the ground. Can feel it, but can't get to it otherwise. Where is that pesky TCCM in that beast?
 

Mike534x

Member
Apr 9, 2012
894
Very helpful thread! Real quick though.... I'm working on the wife's 2007 Saab 9-7x 5.3i. It's AWD and I have no idea where the TCCM is to check the signals at the wires. AWD light comes on with ignition. Sometimes it doesn't, and the AWD seems to work well.... but it always comes on eventually. Showing code C0306 which is that Circuit A/B issue. Clears and comes right back most of the time. Solid center console, so I'll likely have to pull it for the ground. Can feel it, but can't get to it otherwise. Where is that pesky TCCM in that beast?

If you have the square access panel that is located on the driver side of the dash, you should have access to it through the hole. I found this on Google, but the location of it should be the same as shown for this Envoy. @Mooseman may know.
 

Attachments

  • tccm01.jpg
    tccm01.jpg
    182.8 KB · Views: 11
  • Like
Reactions: Mooseman
Nov 20, 2018
4
Ludington
Thanks Mike! I'm going to use this thread to attempt to solve the C0306. I'm sure having the AWD vs. 4WD will be slightly different, but my options are limited. Bad ground. Bad power. Bad Shift motor. Pinched wire. Or.... a bad control module. I saw a YouTube video where a service light for one of these was caused by a bad ABS control mod. No traction light on the Saab, so I'm hoping that eliminates that entire system. Can someone point me to the color schematics for the wires of this specific TCCM.... and opinions on how to best go about checking? The Saab is bone stock.
 

Mike534x

Member
Apr 9, 2012
894
It's not exactly "full time" 4WD, it pretty much engages when it detects wheel slippage
. Most of the guys here term it as the "slip bang system", because of how it operates and eventually strips the splines for the intermediate shaft leading to eventual failure of the system itself. My memory is hazy, but I think someone on here attempted putting the transfer case from a trailblazer to gain back the use of A4WD, 4Hi and 4Lo in a Saab 9-7x. I recall reading awhile back that it was possible to put the all wheel drive transfer case from a Yukon Denali/Escalade into the Saab. Haven't seen it done but there was an interesting article on it.
 
  • Like
Reactions: Mooseman

Forum Statistics

Threads
23,273
Posts
637,484
Members
18,472
Latest member
MissCrutcher

Members Online