service 4wd

I have been getting the "service 4WD" message on the dash. I also have noticed the indicator light for 2wd comes and goes. Sometimes hitting the dash gets it to light back up. Sometimes it doesn't want to shift to auto 4wd or 4wd with out a tap on the dash too. Is this a bad connection on the switch assembly or maybe a bad switch? I found the switches (15709327 Transfer Case Shift Control Switch) on ebay for about $30.

Thanks

There should be a code stored in the ATC module, but if you can get it to act up by tapping the switch, that may be at least one of the problems. Switches and encoder sensors are the usual culprits on those...but really should start by getting the code scanned.

Thanks. I know where to start now.

I have been getting the "service 4WD" message on the dash. I also have noticed the indicator light for 2wd comes and goes. Sometimes hitting the dash gets it to light back up. Sometimes it doesn't want to shift to auto 4wd or 4wd with out a tap on the dash too. Is this a bad connection on the switch assembly or maybe a bad switch? I found the switches (15709327 Transfer Case Shift Control Switch) on ebay for about $30.

Thanks

the intermittent service 4wd message is usually the 4 wd drive select switch. many including myself have had to re-solder the pins on the circuit board where the switch is soldered. if you do not have this ability just get a new switch but inspect the soldering before you pay for it !

i have same issue , sometimes i see a quick flash on dash service 4x4 and then its gone, never been able to pull a code . If it doesn't go into 4x4(little light stays flashing)I stop turn off truck put switch in auto or 4x4 and it goes in . when you say replace switch you mean switch on dash?

i have same issue , sometimes i see a quick flash on dash service 4x4 and then its gone, never been able to pull a code . If it doesn't go into 4x4(little light stays flashing)I stop turn off truck put switch in auto or 4x4 and it goes in . when you say replace switch you mean switch on dash?

you need a drive train GM specific code reader to get the code. as was mentioned in my prior post this is the dash switch which is what you hit to select the 4WD / 2WD mode.

j cAT, out of curiosity, any reason why these switches can't be re-flowed with a heat gun as opposed to re-soldered?

j cAT, out of curiosity, any reason why these switches can't be re-flowed with a heat gun as opposed to re-soldered?

you would use a 30 watt low powered soldering iron for small soldering pins on a circuit board. radio shack has all the equipment to do this work.

I never used heat gun to solder . heat gun would melt the soft cheap plastic. the soldering of these pins takes very low / quick heat and just a touch of very small dia. solder.

sounds like you have not looked at this yet