'06 4wd ST club cab 3.7L Getrag 238 6spd manual trans,152k mi.

There I was warming up the truck in my driveway in 2wd neutral for about 15min and out of the corner of my eye I see a red flash on the lower left corner of the instrument panel.About 5 min later it happened again when I noticed it flash 4Lo off and on by itself intermittently several times and then it stayed out for a few minutes.I turned the radio off so I could listen better and when it happened again I could then hear the transfer case motor cycling at the same moment the 4Lo light flashes.

I'm very concerned that it will do it again at the wrong time while the truck is on the road and ruin the drivetrain.Should I pull the fuse to protect the trans and replace the transfer case motor with a new one?Is that the general consensus when this happens?

 

Yeah, make sure it's in 2wd and pull the fuse, #42.

The issue may be the switch, Transfer Case Control Module (TCCM), or the motor itself.

 

Thank you.I pulled the fuse for now so that I can safely drive the truck on the interstate.The "SVC 4WD" glows on and off while driving as expected since the control module isn't getting feedback from the position sensor within the motor.I'll keep this thread updated as I work my way through the repair and conclusion.

 

I just crawled under and unplugged it. I got tired of it engaging and disengaging randomly. It did it twice on the freeway. I haven't had the time to troubleshoot the module or the motor.

 

Currently going through the exact same problem just pulled the fuse. What was the solution?

 

Still working on it.The shift motor was bad as the sensor pieces were rattling around inside.I replaced the motor with a brand new one,cleaned the connector with contact cleaner and applied dielectric grease,replaced the fuse and a new 4wd switch and then reset the pcm but the "svc 4wd" light still stays on and the 4wd will not engage.I will now look at revisiting the motor connector and sourcing a front control module or having it sent out for repair as new ones have long been discontinued.

 

Ok,another update.The truck is fixed,the 4wd works fine now and no more "scv 4wd" warning on the cluster.It turned out to simply be an unseated connector on the transfer case.As soon as I seated it fully and reconnected the battery and started it up all was fine and it shifted in and out without any trouble.The electrical connector was a real bear to remove and even more so to reinstall and get it fully seated despite my thoroughly cleaning it before and after its removal.

The transfer case shift motor was junk.The mode sensor inside failed and I heard rattling pieces around inside the motor.You can't tell until after removing the motor and shaking it.The mode sensor is integral to the motor so the whole thing has to be condemned.When the sensor breaks it sends erroneous info back to the front control module in turn making it operate the motor to 4wd Lo in order to put it back to 2wd commanded position on the mode switch in the cab.I used a brand new motor from Cardone Select(83306) with a lifetime warranty due to many hard luck stories of unreliable rebuilts and remanufactured failing.

During the repair I took the opportunity to drain the transfer case fluid(ATF+4) and replace the front output shaft seal (SKF 18758) and replace the dried up u-joint on the drive shaft with a Moog/Precision #280 super strength unit with a grease fitting on the end.I also replaced the mode switch on the dash with a new oem unit (68021674AB) as a precaution as it was not expensive and easy to get at and I drained and refilled my manual tranny.All work was done with the battery disconnected and on a slow charger to keep it fully topped up.

I want to especially thank those members and staff that have experienced this problem before and lead me in the right direction.The info here is invaluable if you do some research in the archives.Lots of successful repairs on this and it's usually the shift motor.I'm not blazing any trails here but confirming what many of you already know.