Community Forums

RescueRamsey · 02-13-2019, 06:33 AM

I had the same problems with the same truck at work, once the service 4x4 light is on, the system is locked out, meaning that nothing you try will matter until the code is cleared. Ours ended up being the 4x4 encoder motor. It is the actual electric motor that does the shifting and reports back to the ECU what position it is in.

RobRoy · 02-13-2019, 01:43 PM

Quote:

Originally Posted by TripleEEE

Sounds to me like the transfer case shift motor has failed, especially now that the "service 4wd" light is now on.

Just for the heck of it, I would disconnect the battery for 5 minutes and reconnect. Then go through the procedure again.

We had a rash of shift motor failures on our fleet trucks a few years back.

No go including the TCM fuse ...still no Joy.

Thank for your input

RobRoy · 02-13-2019, 01:53 PM

The problem has been resolved....... he had tried every combo to man including the factory procedure and more than a few times.

A local tech in the Keys came down with a scanner with bi-directional control and re-learned the TCM and all is well.

FYI the shop nor the tech would charge him a dime ....they will both be pleasantly surprised tomorrow.

Thank you all to all that chimed in it's much appreciated

Happy Trails

**JohnRR** · 02-13-2019, 05:51 PM

Thank you for the update they are important for those who may do a search of the subject in the future.

FIRE UP · 02-13-2019, 07:15 PM

Quote:

Originally Posted by RobRoy

The problem has been resolved....... he had tried every combo to man including the factory procedure and more than a few times.

A local tech in the Keys came down with a scanner with bi-directional control and re-learned the TCM and all is well.

FYI the shop nor the tech would charge him a dime ....they will both be pleasantly surprised tomorrow.

Thank you all to all that chimed in it's much appreciated

Happy Trails

As has been stated, thank you for getting back with the remedy. You know, today's "electronically" operated vehicles MIGHT be nice in terms of ergonomics, nice-to-haves, conveniences, do-it-for-you type stuff and all that but, when these electronics SCREW UP, even us old back yard mechanics still do some head scratching.

In the case of your "electronically shifted" transfer case, the old, direct shift ones, (I'm talking older Chevy, Ford and Dodge trucks here) didn't have any input from the vehicle, just the driver. Oh well, that's progress.

Scott

RobRoy · 02-14-2019, 09:51 AM

Quote:

Originally Posted by vettenuts

There was a similar issue with the Colorado. It might be worth reading and trying the below from a GM bulletin:

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Condition/Concern
Some customers may comment on a service 4wd message and the transfer case is stuck in neutral. This condition only occurs when the customer dinghy tows the vehicle or sets the vehicle up for dinghy towing and disconnects then reconnects the battery as outlined in the owner’s manual. Technician will find a c0398 stored in the TCCM (transfer case control module).

Recommendation/Instructions
Verify that the customer has dinghy towed the vehicle or set the vehicle up for dinghy towing as outlined in the owner’s manual and then disconnected the battery with the transfer case in neutral. If the vehicle has a c0398 after this type of procedure clear the diagnostic trouble code and return the vehicle to the customer with a copy of this pi. An owner’s manual supplement will be sent to owners to include steps 5.1 - 5.4. If a customer happens to call your dealership indicating that the transfer case is stuck in neutral after dinghy towing and cannot be shifted out of neutral accompanied with a service 4wd message in the DIC, the following sequence will restore transfer case shifting.

1. With the ignition in the RUN position and engine not running,
2. Open the hood and remove the 30 Amp TREC fuse in the under hood fuse block,
3. Reinstall the 30 amp fuse
4. Continue with "Shifting out of neutral" in the owner’s manual.

Note: Removing the TREC fuse with the key on may cause additional messages to appear on the DIC including service StabiliTrak. After the transfer case is shifted out of neutral turn the vehicle off, restart the vehicle and those messages should not reappear.

My Man! and a PI right from the horse's mouth

That is exactly what this Silverado did and Im sure will do again before he gets back home....and will find the information you have provided priceless.

Im sure until the proper steps of 5.4 and 5.1 are followed in the updated manual as stated in the P.I this issue would just continue.

This is my friends first big trip with the wifey in their beautiful class8 conversion and this issue wasn't a Big Hit with her and down in the keys.

The members here at iRV2 are the best and this valuable resource are priceless.

ps" he took the wifey with some friends last night to " Boondocks" in the keys and showed them how you deal with problems when in the Keys ..... and

" Dont worry B Happy "

Happy Trails

tacboss · 03-15-2023, 07:26 AM

Hi, I found this thread last night after 2 days of grief. Thanks for posting the repair advise GM forgot to include in their owners manual. Pulling the
TREC or Transfer case fuse #6 in the underhood fuse panel worked. Must have the ignition in the "On" position 1st. My problem was I didn't know how to turn the ignition on without starting the vehicle that was new to me.
Note: Push the start button for 7-10 seconds without my foot on the brake & the ignition turns on! Thanks again for the post! 3-15-23