2004 Silverado "Service 4wd" Message

[Hookmaster]

I did look at the earlier thread on this topic. I'll present my situation and maybe someone can point me in the best direction to fix this. The "service 4wd" message has appeared 4 times in the past 4 days. For the first three times, I did nothing and when turning off and starting again it went away. Yesterday I started the car, the message appeared and the light was flashing for the neutral position. I pushed 2wd and the light lit up for the 2wd position. I pushed the Auto button and nothing happened. This morning the message was gone and I could here a motor run for a few seconds when pressing Auto, then 2wd a few times. Should I replace the switch first?

[1968]

Going to need codes on that one.

The last one I saw, had a bad "encoder" in the transfer case shift motor.

Don't replace anything till it's diagnosed.

[jwhjr]

It's usually either the switch or the encoder. As 1968 said try getting the code(s) to help diagnose.

[Jeremy airjer W]

I had my first encoder/motor of the season a couple of weeks ago.

[Hookmaster]

What type of scan tool will detect this? One at an auto parts store or do I need to go to a dealer or repair shop?

[Big Buck Buster]

Snap-On Motus will be able to do this. I don't think that any of the cheaper ones at the local parts store have the capability to do this.

[Jeremy airjer W]

I agree, you'll need a higher end scan tool to get into the 4WD stuff. A "code reader" will usually only get you OBD codes, the more expensive ones might do ABS also.

[Hookmaster]

Do most repair shops and dealers have these scan tools or do I have to start calling and checking?

[Jeremy airjer W]

If you show up at a dealer or full service shop that doesn't have the equipment to check this out than your at the wrong place.

[WingDing2]

I have the same exact problem with my 03 HD silverado and the dealer diagnosed it as an ignition contacts going bad. There are 5 contacts in the switch and they wear out. This information came from the service writer, when I found out the cost to replace the switch I have chosen to drive it until it fails. It always "resets" when I cycle the vehicle. You will notice it acts up more in frigid temps. Airjer you have any experience with this one?

[Jeremy airjer W]

I haven't run into a switch causing a 4x4 problem yet but I have run into many that cause the dash to go blank as your cruising down the freeway and cause the blower motor not to work.

It looks like switched power on that circuit powers up the brake, 4WD, HVAC, Heater, Cruise, and Ignition 3 fuse. If the contacts in the switch where bad than non of those would work. Sounds like there is a misunderstanding? Or I just assumed it was a 1500 h/d with a 6.0 and the wiring changes if it is not. Regardless there is only so much an ignition switch can control so the likely hood of one circuit of the switch exclusively controlling the 4WD system is still slim to none.

[WingDing2]

Great! So now I have 2 problems, because my dash has gone completely blank a couple times with no function of any gauges but they did come back after turning the ignition on and off a couple times. So to fix the "service 4 wheel drive" problem I need to have it diagnosed by the dealer again is what I'm hearing.

[Jeremy airjer W]

the dealer or a good independent shop. We deal with these fairly often. Between the fords and chevys I have replaced about one of everything 2 or 35 times.