claydogg84

Hoping someone can give me a hand, I've been scratching my head all day messing with this truck. It's a 1998 K2500 4x4 with a 5.7l. The 4 wheel drive is not working properly. When I hit the push button for 4 Hi, I can hear the transfer case engaging. After that the light continuously flashes. I checked for power at the front axle actuator - Nothing. I then checked for power at the transfer case switch (3 wire switch on very top of transfer case) - Also no power there. I checked the fuses - All are good. I checked for breaks in the wire harness, and I also came up with nothing. I appreciate all the advice I can get with this, I'm starting to lose my patience.

Jkevin

I had a similar problem with a 95 4x4 and
finally traced every wire from the actuator back.
Discovered a broken wire. What a relief to hear that
actuator working.

claydogg84

Do you remember where the wire was broken? I can't see anything in the harness that looks suspect so I would have to remove the harness completely to check it.

Logan Darriel Collins

the same thing happen with my truck i found out that the 4x4 plunger was stuck
and had to buy a new one check that

Jkevin

Yeah, if my memory serves me it was in the frame rail on the drivers side.
Take a continuity tester and hook to one end of a wire,(you may have to peel
back a small portion of the insulation which you tape up after the fact) nearest
the 4x4 actuator then I used a 5or 6 foot length of wire and traced back as far as
I could on the same color coded wire hook that to the other end of your continuity
tester then touch to another bare spot to see if your light comes on.
If your on the same wire it would make a complete circuit and cause your tester
To light up or make a noise. This allowed me to discover which wire was at fault
and the general location of the fault.

Jkevin

You can google wiring schematic for you truck and possibly
Locate where the wires to your actuator originate. You can also
Possibly hookup a new actuator to a toggle on or under your dash.
I've heard they may be three wire as opposed to two though.

Glenn Larson

Ive been having the Service 4WD message on start up on my 01 Silverado, the push buttons don't light up or do anything. I replaced the push button switch but still had the problem. I took it in for service and they replaced the actuator and that didn't help so they removed it, said i needed a rebuilt or new Transfer case. I didn't replace it. then one day it worked and i told them there must be some corrosion on the wiring, or a corroded connector. They checked that and then said i need a new TCCM transfer case control module. I kept reading about shutting the engine off and restarting it. that didn't work. Then i tried a different routine for starting, I turn the key to the run position and watch the lights on the push buttons and when they settle down, start the engine. I have done that the last dozen times, then when i start the truck. the Service 4WD message stays OFF and the push button Auto 2WD hi low 4WD selector switch works every time. After ignoring all the list of possible cures this WORKED I think a lot of electrical problems come from poor connections and by replacing a $200 whatzit the connections have to be re seated and the component works, dah, and didn't need to be replaced after all. Maybe there is another explanation for why this worked. Id like to hear about it.

99 Silverado 3 door

Does the "Service 4 WD" light come on? I had a similar problem with my 99 Silverado and took it to our local Chevy dealer. They found out the selector switch was shorted out. So, $218 later I drove off with a new switch and no problems since.

Glenn Larson

Your lucky if you got off with just replacing the switch. Ive been having the Service 4WD message on start up, on my 01 Silverado, the push buttons don't light up or do anything.
The routine seems to throw parts at it without ever diagnosing why its not working, first replace the push button switch, then replace the actuator, then replace the TCCM Transfer Case Control Module, and it that don't do it then the whole Transfer case and any other items gathering dust on the dealers shelf.
Ive been reading a lot of the 'cures' for this and most don't include a logical diagnoses other than try this first its cheaper.

cleveland63b

whats the code? contrary to whatever you've read/been told I very rarely have issues after an initial diagnosis on the 4x4 system