I want to get the service 4wd off the message ,I have serviced it but don't know how to erase the code ?

Use scan tool to clear/erase codes.

A blinking service 4x4 light would indicate there are DTC'S - diagnostic trouble codes set . Need a professional scanner to pull these codes , not autozone or advance etc.... How many buttons on the shift selector ? Four or three - this would tell me which transfer case it has an capabilities .
The NVG 263 transfer case features a three button shift control switch located on the instrument panel.
The NVG 236/246 transfer case features a 4 button shift control switch located on the instrument panel
Both systems have a electronic control module .

SERVICE 4WD Indicator
The SERVICE 4WD message is displayed on the driver information center and is an integral part of the cluster and cannot be serviced separately. This message is used to inform the driver of the vehicle of malfunctions within the automatic transfer case (ATC) system. The SERVICE 4WD message is controlled by the transfer case shift control module via a Class 2 message.

Upon seeing this message it is intended for the driver of the vehicle to take his vehicle to a qualified repair shop that has the knowledge an diagnostic equipment to trouble shoot the problem .
These systems can set many codes an without knowing which or if any are set at all you could end up replacing parts an still not fix the problem .
DTC B2725
DTC C0300
DTC C0305
DTC C0308
DTC C0309
DTC C0310
DTC C0315
DTC C0323
DTC C0324
DTC C0327
DTC C0362
DTC C0367
DTC C0374
DTC C0376
DTC C0387
DTC C0550
DTC C0611

Your best bet , take it to a qualified repair shop .

if the 4wd switch doesn't light up to show what mode it is in the tccm will set a code and the 4wd light will be on the fuse is in the under hood fuse block I forget what it is labeled as

Well your mistake was letting them work on it they like to dink people around because they know whats wrong with there computer gadget my thoughts are the plug for the switch try to pull it out and then when you have this issue see if you can wiiggle some wires to see if theres a faultly connection... by the way mechanics prey for and on people like you with multiple codes going for the ones they can claim as the problem even tho they haave had this same issue before but they wont tell you that

Hi there:
The FDCM has a code, and for me to be able to correctly diagnose your vehicle..You will need to get that code retrieved by a scantool.\.

The service 4WD indicator gives an indication to the vehicle operator when the Final Drive Control Module (FDCM) has recorded a Diagnostic Trouble Code (DTC) for an electronic transfer case circuit or component malfunction. This indicator is controlled by the instrument cluster logic circuit based upon cluster programming and electronic messages received by the cluster from the FDCM over the Controller Area Network (CAN) data bus.

The service 4WD indicator function of the reconfigurable dot matrix Organic Light Emitting Diode (OLED) display unit is completely controlled by the instrument cluster logic circuit, and that logic will only allow this indicator to operate when the instrument cluster receives a battery current input on the fused ignition switch output (run-start) circuit. Therefore, the OLED service 4WD indication will always be OFF when the ignition switch is in any position except ON or START. The instrument cluster will turn ON the service 4WD indicator for the following reasons:

Service 4WD Indicator Lamp-On Message - Each time the cluster receives an electronic service 4WD indicator lamp-ON message from the FDCM, the service 4WD indicator will be illuminated. The indicator remains illuminated for about five seconds, until the cluster receives a lamp-OFF message from the FDCM, until the cluster arbitrator logic determines that another display request has priority, or until the ignition switch is turned to the OFF position, whichever occurs first.

The FDCM continually monitors the electronic transfer case control circuits and transfer case shift motor/mode sensor assembly to determine the condition of the system. The FDCM then sends the proper lamp-ON or lamp-OFF message to the instrument cluster, also known as the Cab Compartment Node (CCN).

For proper diagnosis of the FDCM, the CCN, the CAN data bus or the electronic communication related to service 4WD indicator operation a diagnostic scan tool is required. Refer to the appropriate diagnostic information.

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The service 4WD was on and then stayed on ???? DTC'S - diagnostic trouble codes are stored when that message show's . There is a control module (computer) That makes this 4X4 system work . It's a module problem.

What you will need to do is get the codes from the transfer Case control module.(TCCM).This will help in finding the cause.Let me know what codes you find and I`ll be glad to help you further.Good luck.

MOST COMMON IS ENCODER MOTOR
COULD HAVE SWITCH OR WIRE ISSUE
OR INTERNAL T/CASE

First get the codes from the transfer case control module.This will help in diagnosing the problem.You can try pushing the 2hi and 4lo buttons simultaneously for 10 seconds.This should put the transfer case in neutral. Then try going to 2 hi.See if this will get it out of 4wd.Let me know what you find.If you need more help let me know Good luck.

If you had the switch and encoder motor replaced 5 months ago, then you have warranty. You need to return to the dealer and have them pull codes to see if it is the C0327 again. Some of these trucks also had grounding issues for the 4wd module. If it is the same c0327 code stay on them and make them confirm their original diagnosis.