madmatt - Service Four Wheel Drive

[More Power]

My 2001 GMC has for some now illuminated the Service 4WD message at some point into a drive. Might not be for a few miles or a couple hundred miles since the last ignition cycle, but it will illuminate.

Cycling the ignition will clear the message, but it'll return eventually.

Before I get out the multimeter to check the various switch signals on the NVG-263 push-button t-case, any last words of wisdom? I suspect the problem is the encoder motor assy... Thanks....

MP

[DmaxMaverick]

Mine did exactly that early on, like in the first year. I had the button cluster replaced and it hasn't happened since. I think there is a bulletin on it. The dealer new just what to do, and had one in stock.

[Diesel Crat]

Mine has done it a few times as well. Dealer couldn't find any codes.

What's the TSB#? Anyone know?

Only does it when I first start the truck and only stays on for a second. 02 CCSB 43500 miles.

[Tommy turbo]

There is a tech bulletin on this. Did you ck transfer case codes? this should give you a clue. I do change lots of dash switches. Very seldom the motor drive. I have found a bad ground behind instrument cluster as well. Ck codes first.

[White Truck]

I'm bettin' you'll find a B2575, caused by the dash switch. Common failure.
:eek:

[More Power]

Thanks guys! The Predator reports no codes - zilch.

I'll check it again when the message reappears.

Anyone discover the bulletin on this problem?

Thanks again,

MP

[madmatt]

Service 4WD Indicator Illuminated, DTC B2725 Set (Replace Transfer Case Shift Control Switch) #02-04-21-004 - (Apr 15, 2002)
"Service 4WD" Indicator Illuminated, DTC B2725 Set (Replace Transfer Case Shift Control Switch)
1999-2002 Chevrolet and GMC C/K Pickup and Utility Models (Silverado, Sierra, Avalanche, Suburban, Tahoe, Yukon, Yukon XL)

with Four Wheel Drive and NVG 236/246 Transfer Case (RPO NP8)

Condition
Some customers may comment on the Service 4WD indicator illuminating. Upon investigation, the technician may find DTC B2725 set.

Cause
The condition may be due to a intermittent fault in the transfer case shift control switch.

Correction

Important
The transfer case shift control module should not need replacement. DO NOT replace P/N 15749703 unless diagnosis points to the module as the malfunction.


Replace the transfer case shift control switch using published Service Information procedures.

Parts Information
Part Number
Description

15709327
Transfer Case Shift Control Switch

[madmatt]

Also I think the predator only reads powertrain codes and not tccm codes, although I'm not sure. Even if you don't have the code, it's probably the switch. I've replaced like two encoder motors and probably two dozen of these switches :eek:

[More Power]

Thanks guys... I'll replace the sw, then report back.

BTW - The 2500HD/3500 with the pushbutton NGV-263 transfer case is RPO code NP1.

MP

[Diesel Crat]

Ditto on the Bulletin THANKS... :D :D :D

I'll have the dealer check it again as its almost due for an oil change.