what part causes 4wd to not electronically switch back and forth? ive got a service 4wd light on my 5.3 chevy silverado 2000

 

My 2005 had a similar problem. It was intermittent. At some times it would even cause the truck to run bad. My problem was a computer part in the 4wd system that needed replacing. You have to take it to the dealership while the error is showing, and do not let them clear the code to get the mileage. I did this for 3 months until I realized what was happening and made them not clear the error until the tech looked at it.

 

Yep mine has been intermittent as well for over a month now. The 4wd sometimes will be not want to switch over. . . then at a later time it works fine? ? ? Do you have any idea what part they changed? Chevy wants 200.00 just to hook it up. I would rather throw a part at it to be honest. When you say it would sometimes make the truck run bad what did you mean? Im curious as some times I wonder if my truck it running the way it should. . . sometimes feels a little hesitent on the low end then a i get a surge of power. Could just be me, or the truck being a bit cold. I would like to get this fixed though. I wish i knew what fixed your truck i would buy that dang part and slap her in there, and unhook the battery for 24 hours.

What do you mean dont let them clear the code to get the milelage? I dont deal with stealerships very often so how do they usually get the mileage? I would guess they could just get it by looking at the dash, but I cant see that clearing the code so you must me something else, maybe they hook it up under the wheel.

Im new to this electrical engine jargin so you might have to explain it to me barney style. The only proof i have of this problem is the interm. 4wd issue and the check 4wd light, if the code is internally popped, will it stay showing even if the truck isnt displaying the service 4wd light when i take it in?

 

I just found the paperwork, the part was thr 4wd encoder motor. The dealership tried to reprogram it with no relief, They finally replaced it. As far as clearing the code, on my dash the milage and any problems like "check coolant", "low fuel", "service 4WD", etc. appear on the same digital readout. So if the truck says "service 4WD" you cannot see the milage. So they would press the button on the steering wheel to change to milage and the code would disappear and not return. Once this was done the truck showed no trouble codes when hooked to computer but as long as "sevice 4WD" was showing on the screen It would show a trouble code. Makes no sense to me.
As far as running rough (and this only happened 1-2 times), the truck would studder, try to startin the wrong gear, and shift gears sporatically.

 

Well I do have the mileage blanked out right now which I've been wondering whether it was related or not. I took the switch out of the dash and soldered a certain spot which looked like the solder might have fallen off. I went ahead and hit some other spots up as well. The truck switches from A4WD,2WD, and 4Hi with no hesitations but ive only done it a couple of times while driving in town. Its too early to call it good but I am hoping the problem is fixed.


I just went outside and pushed the mileage button on the dash to cclear it and nothing happened. Its still blank, and i have no 4wd light? ? ? When your mileage was blank did you have the 4wd light?

 

In my case, it was just s switch behind the buttons. I was locked in 4wd low, then just locked up, Truck refusing to move at all-> 30 miles in. I removed all PCM fuses, E/B as well, sat 15 mins and inserted in reverse. 4x lights stopped flashing, everything returned to normal and I got out. I had mine replaced long ago under warranty. Took them 45 mins and they did not re-program anything. There is a TSB on it; YET, I am sure there are other reasons as well why this happens. When enough people complain, we will know.
TSB #020421005 -- SOME VEHICLES WILL NOT MOVE WHEN 4-WHEEL DRIVE IS REQUESTED, NOISE, SHUDDER, POOR PERFORMANCE, TRANSMISSION / TRANSFER CASE SLIPS, TRANSMISSION WILL NOT UPSHIFT, SLIPS IN 4-WHEEL DRIVE. *TT (NHTSA ID #634905, JUNE 01 2002)

 

When i went out to my truck the next morning the milage and transission lights were up and running. . . I have not had the 4wd light since b4 i soldered the switch, and the transfer case shifts with no problems. Its only been lightely ridden for two days so Im not calling it good just yet. The only noise from underneath is what i believe to be the motor moving things from 2wd,4hi,4lo, and auto4wd.

Ill keep an eye on here nice and close as even when i had the problem with this the mileage and tranmission lights were off and on, just depended on the truck mood i guess.

 

The only other thing I remember that I forgot before was on the 4WD indicator lights all were lit up- 2WD, N, 4LO, 4HI. Showing that all were on at same time (not possible).

 

Hey Bluez,
Keep us posted on whether your problem is fixed. I have the exact same symptoms. My mechanic says I need to replace the (don't remember the part name) chain that actually shifts it into 4W... he said GM used a plastic band but they tend to get stretched. The replacement is an actual chain. I think I'll have a look at the back of the switch first!

 

I had a friend with a 2000 silverado that had the same issue with all the lights lit and "service 4wd" showing on the dash. He brought it to dealer and they replaced the selector switch on the dash. No problems since. Maybe they had some bad switches that the connections come loose. I have a '99 and have never had problems.