Service light on the 4 wheel drive

The 4X4 system is controlled by a electronic control module . Can set a number of DTC'S - diagnostic trouble code's . Having the vehicle check for DTC'S would be your best bet ! Not at autozone or advance or any parts stores . They can not pull these code's . Need a factory or professional scanner . Your best bet , take it to a qualified repair shop.

I would check to make sure the correct ECM is installed in this auto right away before adding anything else to this truck.Check it like the shop should have, this angers me so when i hear this stuff. Neither shop should have been paid for bandage solution. Then get back to me.

The service 4x4 light coming on indicates problem with the system an DTC'S - diagnostic trouble codes are stored . Before replacing parts have a qualified repair shop do diagnostic's . ! Guessing an replacing parts on electronically controlled systems never fixes cars.
Do you know what DTC'S are ?
DTC B0775
DTC B0780
DTC B0785
DTC B0790
DTC B2725
DTC C0306
DTC C0379
DTC C0387
DTC C0396
DTC C0550
DTC C0569
DTC C0896
DTC P2160 or P2161
Which transfer case does it have ?
Transfer Case - BW 4485-NR3
Transfer Case - MP 1222/1225/1226-NQG
Transfer Case - MP 1625/1626-NQF
Transfer Case - MP 3023-NQH
Transfer Case - NVG 261-NP2

Replace switch its bad.

needs oil you might have an oil leak,but what you tell me it sounds like no oil.adrian,,,,

Usally these warning lights come on for a reason.
I would have someone plug a OBD II reader in and retrieve the code.
The code should be able to tell you specific information on why the light is on.
Until you find out I would not us the 4 wheel drive function.

I recommend taking this vehicle in for a basic transfer case inspection and switch inspection as well. this light will illuminate if the case is experiencing difficulties in shifting or engaging the 4WD system.

The service 4 wheel drive light comes on because there's a problem. The biggest causes of this I've seen are a software glitch in the final drive control module which the dealer can fix by reprogramming and the other is usually the electric actuator on the front axle housing. The only light that comes on by a timer is the one that says, "perform service" in your overhead console or odometer.

If you have push button 4-Wheel Drive, it is recommended that you use it every once in a while, in order to keep gunk, rust, and corrosion to build up on moving parts. The mostly likeley (though not definite) reason would be that you let the 4-wheel drive unused for so long that corrosion has built up on the parts and the actuator that engages the 4-Wheel Drive doesn't have the power to engage it past the corrosion. You'll need to take it in to be cleaned, or to have parts replaced. In the future, every month or so, engage 4-Wheel Drive and drive around in some mud, grass, sand, or any other loose ground for a bit, just to keep the parts moving and clean.

The service Four wheel drive light is to alert the operator the system is not being read properly by the ECU.

If the ECU loses contact with or position of the Transfer case actuator motor the service light will come on. Same thing goes for the front diff actuator.

So it may be a bad switch, sensor, or an actual problem in the 4WD linkage. This is not a Oil Change light that you can ignore a few extra weeks - it indicates a problem that should be taken care of ASAP to avoid costlier problems down the road.
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try disconecting the battery to reset service light may not solve the problem but should allow u to put truck into 4 wheel