Please tell me wherethe TCCM is on an '04 Sierra!!

I have a 2004 GMC Sierra 2500 LD 4x4 with the electronic 4WD, including the Auto 4WD position on the control. The truck hasintermittently displayed the dreaded "Service 4WD" message for a while, and I have tried various things to fix this.Replacing the control switch on the dash did not help. The 4WD functions work perfectly some times; at other times the 4WD system has a mind of its own. It randomly switches from one mode to another, or the lights on the switch don't illuminate, or the neutral light will come on while it is not in neutral, etc.

The next thing I may try is replacing the Transfer Case Control Module. But I can't find the darn thing. My Haynes repair manual gives a detailed description of where the TCCM is located - behind the headlight switch. I removed all the switches at the left side of the dash and found the spot where the TCCM should be, but the slot is empty. GM must have moved the TCCM to another spot for '04, but where? I tried tracing the wiring from the switch but it disappears into a larger harness. I hunted around under and behind the dash for an hour or two and even removed the speedo cluster, but can't find it.

Any ideas or experience with this?

Thanks in advance.

 

its back there..you'll have to remove a fair amount of the dash...but..it ain't bad...i've not seen 1 yet...bet on the encoder motor if you've already thrown a switch at it

 

I thought it would be there too, but it's not there. I removed the entire top left corner of the dash, including the large plastic piece that holds the 4WD switch, headlight switch, dash heater vent outlet, and fog light/box light switch. And I also removed thespeedometer cluster.That exposes the area quite well. I can see the slot where the TCCM should be, but it is empty.The Haynes manual shows that same slot with the TCCM in it.

If the TCCM is not in the usual slot, where else could it be? Did GM place it in a different spot for 2004? With all the complaints about water from windshield leaks dripping on the TCCM units, possibly GM relocated them?? Just a thought.

 

its in there..its behind the wall you saw when the cluster was out..but lower...get under the dash and go up,right next to the firewall...but over by the drivers door...i think what i've done is removed the fusebox on the end of the dash to get at it..

but again...that part ain't bad..

is it setting a c0327?

 

Argon, I don't have access to a code reader and have relied on information found by searching the internet. Admittedly, that information is guesswork and not necessarily reliable. Replacing the switch seemed a good starting point. And various posts pointed to the TCCM as prone to failure. And it seems that the encoder motor or the encoder motor sensor also often fails.

One reason I haven't looked too hard for a code reader is that many seem to think that the codes often aren't reliable indicators of the true problem. But I would like to see if there are any stored codes and to rely less on guesswork. Can you tell me how sophisticated a code readeris neededto read these codes? What model or specs of code reader will do the trick? Or do I need to take it to GM and pay their labor rates?

 

yep..gm..an autozone type scanner will not "talk" to the tccm...sometimes,its cheaper to pay up than to guess.......and guess........and guess....

 

Does anyone here know much about the ELM 327 interfaces that allow one to use a PC as a scan tool? Apparently various software options, including some shareware, are available to make this work. As an example, here is one currently on eBay:
http://cgi.ebay.com/ebaymotors/SCAN-...spagenameZWD1V

Is this a waste of time or will this read the codes and allow for two way communication, etc.? I'm a newbie when it comes to dealing with these computerized systems and don't know whether to trust the claims made by the sellers of the ELM 327 kits.

 

SUCH THINGS ARE only going to read codes in the pcm..they will not retrieve radio,cluster,bcm codes,etc..including your tccm..

they are also read-only...no bi-directional functions....which is ok if ya just need to turn a light off

 

The intermittent and unpredictable problems with the shift switch continue, and occasionally the Service 4WD warning appears.

We hooked the GMC to a scan tool and found no active codes but found two codes in history; C0327 (Transfer Case Encoder Motor) and C0379 (Front Axle Actuator).

I ordered a new Encoder Motor (got a good price), knowing that the problem likely just is with the sensor in that motor.

Can anyone tell me whether a faulty Encoder Motor/Sensor could also cause the C0379 code, or should I be looking at changing the Front Axle Actuator as well? I can get a new one quite cheaply.

Also any installation tips on installing the Encoder Motor will be appreciated. The Haynes manual does not go into details about what position to have the transfer case in and what position to have the new encoder motor in during installation.

 

neutral..

didja get a gm motor?..how much?