ok, i checked the 4x sticky...lots of info but nothing i could use "yet"

so what is happening is this.
last month i would turn off the truck and then restart sometime later..(time span didnt matter) and the 4 button on the dash wouldnt light up and then i had 4x service light come on.
the switch would light when i turned key to first position but when i went to start the truck nothing.
it did this about 6 or seven times then it never happened again...i chalked it up to corrosion or something...was being lazy and cheap.

so now its back again.
i checked the harness at the tccm behind kick panel with battery disconnnected...no change.
i then drove around rest of day still no 4x...at this point i became worried because it always magically fixed itself..not this time.

then on way home..got gas..fired back up and taa daaa 4x works fine.
i have shut it off and on twice and its back to normal.

my question is this...anyone exp anything similar?? the tccm shows no external signs of corrosion though.
could it be internal corrosion causing a short??
i am thinking its elec so on my days off i am checking connections at encoder and fuses and switch in dash. i hope its a simple fix...mechanically all seems fine.

thanks guys...sorry to be kinda vague...i tried searching but either i didnt phrase it right or just didnt dig deep enough.

 

The encoder motor is prob corroded

if its not pack it with electrical grease while ya have it out

did ya try to pull the 4x4 codes yet ?

 

If the 'Service 4wd' light was on, there should be a stored code in the TCCM, but you'll need a full feature scan tool with enhanced GM interface to access the TCCM to check for codes. If you've reset power to the TCCM, the codes will be erased.

It sounds more like a bad ground or power wire somewhere in the system. Use the NV236 wiring post in the tech article section to guide you and check the continuity of all of the wires between the switch, TCCM, and encoder motor.

 

Thanks for the leads guys..i think there is a shop in town that will scan 4x codes...a buddy told me to check them out. Looks like i have some homework to read up on.

 

ok, found the cause. i went elec hunting...switch was good...so i moved to tccm.
it was the tccm harness at the connectors.
i cleaned them up and all is good.
HOWEVER...now my speedo pegged itself at 100mph when i reconnected the battery and fired it up....i will be doing some more searching it seems.
most likely will disconnect battery again and see what happens.

thanks again guys for the leads.

 

did you clean the speed sensor harness ?

 

no, i never got that far.
i started in the cab...and was hoping for the best...i checked the part...then fired up to check for 4x light.
i figured i would just check each part till i found something (or got lucky)

i am guessing there is a speed sensor on front axle?

 

nope i think there should be one on the tcase I know there is one on the 233cs

 

Well...what luck pulled into work this morn...and ping...all is good.

 

sounds good to me =P hows the 4x4