"service 4wd"... Saga Continues...

[TedH]

OK...

 

I installed the new 4WD Selector switch from www.gmpartsdirect.com this morning. The 4WD appears to switch more smoothly between the settings (2H, 4H, 4L, Auto 4WD) and does not get 'stuck' in any of the settings BUT I still get the 'Service 4WD' message once the transmission enters third gear when I first drive it (if I press the trip odo button, the message clears from the display and only re-displays if I turn the truck off and get to 3rd gear again).

 

Should I have the computer code (C0300) cleared? If so, I'll have it done today and then see if the message returns.

 

If this doesn't clear the problem, I'm inclined to have the ECM (ECU?) re-flashed to reprogram the 4WD as other threads have suggested.

 

...Actually, I just checked and the recommended action from Chevy is to to "Reprogram the TCCM (Transfer Case Control Module)'...

 

This is an interesting thread on this code/procedure (burning in the 'software'): http://findarticles.com/p/articles/mi_qa38...i_n9410293/pg_5

 

Then, if that doesn't resolve it, I'm guessing I need to have a mech diagnose the transfer case for issues and possibly replace the electric 'motor' that is on the transfer case (at least it is my understanding there is an electric motor mounted on the transfer case that helps manage the 4WD).

 

Will advise...

 

NOTE: I bought two switches. One in error for the 99-02 (PN 19168767 this is the 'new' switch that replaced the old switch...) and my switch for the 03-07 models (15136039). If anybody with a '99-02 needs the new in-dash switch, I'll sell it for the price of the part $43 + S/H. I'm re-using the box and packaging it arrived in Thursday so S/H should be reasonable ($10-12 is my guess). Let me know if interested.

 

My orig thread that asked for a step-by-step for the switch replacement (that helped as I had no idea how to remove the dash bezel):

 

http://www.gm-trucks.com/forums/index.php?showtopic=84347

[DofD]

You've definitely done your homework on this.

 

If it were me, I'd start with having the code cleared. Then if that doesn't work then I'd move onto the "Reprogram the TCCM".

[TedH]

I do think the 4WD switch was failing... all of its lights had gone out one time and it even showed 'N'eutral when I was driving once. Also, it would hesitate to change between the settings (which prompted me to replace the 4WD actuator first). I suspect the TCCM will need updating but will advise once I have the C0300 code cleared Saturday morning.

[pm26]

I really miss the old transfer case lever on my ;95 Nissan. As reliable as it gets. Have we gotten so lazy that nobody can push the lever anymore? It seems incredible how complicated electronic transfer case controls have become.

[TedH]

I really miss the old transfer case lever on my ;95 Nissan. As reliable as it gets. Have we gotten so lazy that nobody can push the lever anymore? It seems incredible how complicated electronic transfer case controls have become.

 

Yeah, I've read the manual systems had ZERO issues. So much for switches and wires... look fancy on the dashboard (press a button and... voila!) but what a royal pain in the butt!