Service 4WD Message

[bluebear15]

I recently bought a 2005 Suburban Z71 from a private seller. I test drove it when I bought it and the 4WD was working at the time. Beginning last week, I randomly have been getting the "Service 4WD" message. I was in an accident that totaled my prior 2006 Tahoe Z71 and the 4WD always worked no problem. I saw that the 4WD switches go bad so I grabbed mine from my 2006 Tahoe and swapped it in but still had the same issue. I've also read might be something with the controller that you have to change along with the switch? Any one have ideas on what might be wrong or what I should check? I can easily swap parts from my 2006 Tahoe.
Thanks.

 

[George B]

You need to have someone read the codes form the TCCM to determine the issue. post those codes up here when you get them.

 

[bluebear15]

You need to have someone read the codes form the TCCM to determine the issue. post those codes up here when you get them.

I thought there were ways to diagnose it without having the codes read. These are the ones that can only be read by a TechII right?

 

[George B]

I thought there were ways to diagnose it without having the codes read. These are the ones that can only be read by a TechII right?

Some higher end readers can see them. You have several components that could be at fault so knowing the code is important. Unless you want to just throw parts at it.

 

[Fless]

A bidirectional scanner (like a Tech 2) would be the bomb for your situation. Otherwise you're groping around in the dark.

Some simple things: check and clean all grounds and ground cables, especially the two grounds that are on the body, behind the LF wheel well, behind the rocker panel (not a really good place for a ground connection, but it is what it is). Also the engine to firewall ground from the back of the driver's side head. It's probably braided.

Battery cables to see if they're rotting inside the jacket.

You can check the TCCM 5v reference at the input to the 4x4 switch. When you turn the key on, do the mode lights on the 4x4 switch cycle through (Auto, 2hi, 4hi, etc.)?

After that, check the encoder motor on the transfer case. Sometimes those harnesses get loose and hit the driveshaft. Check connections and swap yours out from your Hoe if they're the same.

Curious about what you find.

 

[Andrew Smith]

I recently bought a 2005 Suburban Z71 from a private seller. I test drove it when I bought it and the 4WD was working at the time. Beginning last week, I randomly have been getting the "Service 4WD" message. I was in an accident that totaled my prior 2006 Tahoe Z71 and the 4WD always worked no problem. I saw that the 4WD switches go bad so I grabbed mine from my 2006 Tahoe and swapped it in but still had the same issue. I've also read might be something with the controller that you have to change along with the switch? Any one have ideas on what might be wrong or what I should check? I can easily swap parts from my 2006 Tahoe.
Thanks.

 

[Andrew Smith]

I recently bought a 2005 Suburban Z71 from a private seller. I test drove it when I bought it and the 4WD was working at the time. Beginning last week, I randomly have been getting the "Service 4WD" message. I was in an accident that totaled my prior 2006 Tahoe Z71 and the 4WD always worked no problem. I saw that the 4WD switches go bad so I grabbed mine from my 2006 Tahoe and swapped it in but still had the same issue. I've also read might be something with the controller that you have to change along with the switch? Any one have ideas on what might be wrong or what I should check? I can easily swap parts from my 2006 Tahoe.
Thanks.

Check your grounds on the frame located under the driver door by the body mount first on 2000 to 2006 models. They tend to rust up north. Then the 4wd switch on the dash is the next thing to check. When both those are fine its normally (in my experience) the encoder motor ring inside the encoder motor that goes out or the plug to the encoder motor.

 

[JonnyTahoe]

Your lucky you have a ''Parts Truck'' so do I. My Tahoe has the T-Case removed so all the connectors that plug into it (Like 5 of them) are not connected so when I start the engine once in awhile to warm it up and charge the battery my Service 4WD message comes on. it can be from loose connections/connectors. If your Truck is working fine and you keep getting that message you may be able to clear it for awhile.