2008 Silverado - Service 4wd System

[Mossyoakglock]

I got the “Service 4wd System” message on the DIC yesterday afternoon. I left work and it was not on. Drove about 20 minutes to the store and when I came back out I got the message. I turned the truck off and then turned just the ignition back on and the message was still there. Started truck and still had the message. I cleared it with the check button on the DIC and drove home. Got to the house and tried to switch to 4H and 4L but it would not engage. Pulled in the garage and turned the truck off. I then hooked up my scanner to see if there were any codes which there were none (no other lights either). The truck was off for maybe 5 minutes. Started the truck and got no message and it would shift into 4H, Auto and 4L with no problems.

 

I checked all the fuses and all are fine and also checked all the connections around the transfer case and all seem to be connected and clean.

 

Got in the truck this morning with no message. Thoughts on what could be wrong?

 

In the little research I did it could be the fuses (all good), connections (all good) or the dash switch. Most common seems to be the dash switch but could it the actuator on the front axle?

 

 

 

[Armo325]

I had the exact same issue on my 2005 Tahoe a couple years ago.  As you already mentioned, the switch was the culprit. Fortunately, they aren't too expensive and very easy to replace.  I didn't replace it for quite a while after the problem started only because it happened so infrequently and didn't affect my daily driving.

 

If it happens again, take a look at the switch.  When it happened to me, all of the lights were off on the switch when the "2WD" light should have been illuminated.  For me, that was the biggest hint the the issue was in the switch and not elsewhere in the truck.

[Mossyoakglock]

My switch is a knob and the little light was on 2wd but when I tried to rotate it the light didn't move. It stayed on 2wd even though the switch was in the 4H/4L position.

 

Could it be cold related. It's been really cold here in TN. Colder than normal for an extended period of time.

I think the highest high it has been here in Nashville in a few days is 34* with the average high the past week being 25ish. Lows in the mid-teens. The switch is only around $25 so I might just go ahead and replace it

 

**Edit** -

If I got the message, would there be a code stored in the computer?

I scanned with my scanner but nothing showed up. Wasn't sure if it would store a code that cannot be read by a handheld reader.

[carnau]

3 hours ago, Mossyoakglock said:

My switch is a knob and the little light was on 2wd but when I tried to rotate it the light didn't move. It stayed on 2wd even though the switch was in the 4H/4L position.

 

Could it be cold related. It's been really cold here in TN. Colder than normal for an extended period of time.

I think the highest high it has been here in Nashville in a few days is 34* with the average high the past week being 25ish. Lows in the mid-teens. The switch is only around $25 so I might just go ahead and replace it

 

**Edit** -

If I got the message, would there be a code stored in the computer?

I scanned with my scanner but nothing showed up. Wasn't sure if it would store a code that cannot be read by a handheld reader.

If these is a light... there is a code.

You need a code reader that will read ATC information. I am looking into a Bluedriver as we speak and I will post a video and comments on it when I get it. It looks like a good reader.

 

With that being said. Yes the switch is normally the problem on these vehicles. I made a video on the replacement.

The code is normally a B2725 but I have seen other codes still caused by the switch.

Here is the part you will need to replace it. - http://amzn.to/2BScDVv

Here is the video.

 

[Mossyoakglock]

There was no light, only the message. Would a message trigger a code even though there is no check light?

[davester]

Yes, there are about 10-15 computers in your truck, all of which can generate codes.  Most cheap handheld ODBII code readers can only read codes from 1 (the ECM), more expensive ones can do a few (airbags, transmission, abs), past that you get into TechII, or software like Autogenuity w GM Enhancement.

 

The CEL only comes on for an emissions-related problem, 4wd isn't emissions-related.

[carnau]

3 hours ago, Mossyoakglock said:

There was no light, only the message. Would a message trigger a code even though there is no check light?

The message is considered the warning light.