Service 4wd

DM28 · December 22, 2008

dear tech,

yesterday i was driving home, it was snowing and i pressed the auto 4wd. drove 20 miles on freeway not going over 50mph due to conditions, and everything worked fine. got off freeway and engauged into fulltime 4wd. no more than a mile later my info center said service 4wd. so imediately went into 2wd and it went in. i didnt try yet to go back into full time 4wd to see if it will. i hit the info button and it said, auto lock, auto unlock, remote lock, remote unlock feedback. what do you think? i will assume i cant use my auto 4wd, which is ok, as long as i can still engauge into full time 4wd, and back to 2wd. any help is appreciated.

trailboss05 · February 8, 2009

ok, Hi everyone. I'm a first timer user here and have a question on this topic. I just bought a 03 Tahoe and brought it home today. I thought I try the 4WD and hit the button for 4high and it engaged but it was somewhat noisy and dragging a bit. I flipped it into AUTO and it quietened right down and the dragging stopped. I could tell it is now in 2WD. Then the service message flashed on the message center, SERVICE 4WD, and the red neutral light is displayed at the selector switch. I stopped and tried to re-engage the 4HIGH selection but nothing. Just the red light saying neutral.I suspect it wasn't used too much by the previous owner as they used it as regular city driving, but only guessing. I was reading this posting and could this be a servo problem? I bought it privately and really don't have a warrenty or nothing.Any help is welcome before I call the people I bought it from.

Matt_ · February 8, 2009

If you turn your truck off and then on, does the red light on the switch stay on?

I'm also assuming, from your post, that you are able to drive it around right now and it feels like you are in 2wd- correct?

MarkD · February 7, 2009

Truck bills '09

Whatever this encoder motor costs ~$800

New Instument cluster~$330

Repair G80 ~$600

Cigarette lighter short ~ $75

CD player quit ~?

VMax2007 · February 7, 2009

Truck bills '09

Whatever this encoder motor costs ~$800

New Instument cluster~$330

Repair G80 ~$600

Cigarette lighter short ~ $75

CD player quit ~?

Mark, how many miles on your truck? GM extended the warranties on the cluster in the 03/04 trucks to 75,000 miles. If you have less than 75K miles, you should have gotten this fixed for free.

jbordi · February 6, 2009

This may help.

TECHNICAL

Bulletin No.: 05-04-21-003C

Date: April 15, 2008

Subject:

Service 4WD Light Illuminated, DTC C0374 Set (Inspect Wiring Harness to Transfer Case Speed Sensors,, Replace Wiring Harness) Models:

2004-2007 Buick Rainier

2003-2006 Chevrolet Avalanche, Suburban, Tahoe

2003-2007 Chevrolet Silverado Classic, TrailBlazer, TrailBlazer EXT

2003-2006 GMC Yukon, Yukon XL

2003-2007 GMC Envoy, Envoy XL, Sierra Classic

2003-2004 Oldsmobile Bravada

2005-2007 Saab 9-7X With Four Wheel Drive or All-Wheel Drive

and Active All-Wheel Drive (RPO NP4) or Active Two-Speed (RPO NP8) Transfer Case

Supercede:

This bulletin is being revised to update the Model and Warranty Information. Please discard Corporate Bulletin Number 05-04-21-003B (Section 04 - Driveline/Axle).

Condition

Some customers may comment on intermittent illumination of the Service 4WD light. Upon investigation, the technician may find DTC C0374 set. The customer may also comment on intermittent erratic operation of the 4WD or AWD system after driving through rain/snow or simply going through a car wash.

Cause

The speed sensor signal may have become corrupted. Possible openings in the speed sensor wire insulation (twisted pairs) can allow water intrusion. Also wire connections contaminated by water may result in short circuits and erroneous speed sensor readings. This most often occurs on the rear speed sensor circuit.

Correction

Inspect the wiring harness to the transfer case speed sensors. On Rainier, TrailBlazer, Envoy and 9-7X models, fabricate a replacement speed sensor harness between the C101 connector and the speed sensors. Completely inspect and test all wiring. Refer to Speed Signal Front Axle Actuator and Indicators schematic in SI.

Replace the affected twisted pairs. Do not over-twist the two wires in the replacement harness. Wires should be twisted at a rate of 9 revolutions per foot. Use service connector pack, P/N 88987993 at the speed sensor end and terminal, P/N 15326267, at C101.

Terminal testing tools and service terminals can be found in Terminal Repair Kit J 38125. Terminals are available from SPX/Kent-Moore.

The smaller transfer case harness splices into the larger chassis harness a few inches in front of the crossmember. The chassis harness routes along the left side of the frame under the driver door area. Use nylon tie straps to secure the fabricated harness to the main chassis harness between the transfer case and C101.

On the full-size pickup and full-size utility models, replace the 2.2 m (88 in) pigtail harness that runs from the C151 connector under the hood to the transfer case. Use either harness P/N 15832722 or 15224663 depending on vehicle equipment. Refer to Propshaft Speed Sensors Front Axle Actuator and Transfer Case Shift Control Switch schematic in SI.

Important: Technicians should verify the integrity of the splice joints after the repair. All splice joints and connections should seal properly against water or a repeat condition can occur.

trailboss05 · February 8, 2009

If you turn your truck off and then on, does the red light on the switch stay on?

I'm also assuming, from your post, that you are able to drive it around right now and it feels like you are in 2wd- correct?

Yes, the light goes out and I can still drive it , I assume in rear wheel drive

Matt_ · February 8, 2009

Try switching your truck to Neutral, let off the brake (dont roll into anything!) to relieve any stress in the trans & tcase, and try putting it into 4 hi again. If the same thing happens, you'll likely need a new shift motor. However there is the ever so slight possibilty that the 4x4 hasn't been used in a long time resulting some of the seals to sort of bond with the parts. Making it as easy as possilbe for the truck to shift into 4x4 may allow these parts to free up.

Edit... hold on, let me read your post again. I skimmed it the first time and just skimming it again i think it may be something else. I thought you said it made noise trying to go into 4hi, not that it made noise as you 'drove' it in 4hi...

Matt_ · February 8, 2009

I thought I try the 4WD and hit the button for 4high and it engaged but it was somewhat noisy and dragging a bit. I flipped it into AUTO and it quietened right down and the dragging stopped.

Were you on a wet/slick surface when you put it into 4 HI? If not, the noisy/dragging was because you were stressing out the drivetrain from being in 4 wheel drive with good traction... lol dont do that! not good (i have a side story there, has to do with a salesman taking my 05 for a drive).

In any event, the fact that it quieted down in AUTO is a good sign, since in AUTO your front axle is still engaged. So there is likely no problem with your front diff actuator and/or your front diff. Since your "service 4 wheel drive" message came up, best bet is to get the code read at this point to see what triggered the code.

Edit... maybe it'll help if you clarify EXACTLY what you did and heard. lol cause reading it again, it could go either way.... was it noisy while driving in 4HI, or just noisy trying to shift into 4HI...

trailboss05 · February 8, 2009

Try switching your truck to Neutral, let off the brake (dont roll into anything!) to relieve any stress in the trans & tcase, and try putting it into 4 hi again. If the same thing happens, you'll likely need a new shift motor. However there is the ever so slight possibilty that the 4x4 hasn't been used in a long time resulting some of the seals to sort of bond with the parts. Making it as easy as possilbe for the truck to shift into 4x4 may allow these parts to free up.

Edit... hold on, let me read your post again. I skimmed it the first time and just skimming it again i think it may be something else. I thought you said it made noise trying to go into 4hi, not that it made noise as you 'drove' it in 4hi...

I just wet outside and started it up. The message center still says service 4WD and there are no lights at any selector. I tried pushing any of the buttons and nothing changes.

Matt_ · February 8, 2009

I just wet outside and started it up. The message center still says service 4WD and there are no lights at any selector. I tried pushing any of the buttons and nothing changes.

If that's the case, you need to get the code read. This doesn't have to be done at the dealer... most good shops can scan the TCM for codes.

If you get that code, we can help trouble shoot further. Otherwise, anything from this point on is a guess and you'll just be throwing parts at it.... But don't lose sleep over it, it's likely something that can be handled without much trouble

trailboss05 · February 8, 2009

I just wet outside and started it up. The message center still says service 4WD and there are no lights at any selector. I tried pushing any of the buttons and nothing changes.

If that's the case, you need to get the code read. This doesn't have to be done at the dealer... most good shops can scan the TCM for codes.

If you get that code, we can help trouble shoot further. Otherwise, anything from this point on is a guess and you'll just be throwing parts at it.... But don't lose sleep over it, it's likely something that can be handled without much trouble

ok....I'll take it to my dealer as they are pretty good with my past vehicles I bought there and get them to scan it and run the VIN for any service updates that can be done, if any.Thanks for your help and I'll let you know what I find. Its a bit disheartening as I just bought it and this thing is mint and orginal and was brought up from Florida. I had to push the old owner to sell it to me and going back to him is probely not a option.

norsemanberg · February 7, 2009

This happened to me yesterday when I used my 4wd in the snow. Now, occasionally, I have no lights at all to the switch. Occasionally, I have the red light.

Advice? Should I buy parts and replace or get a dealer, to read the code and lighten my wallet?

I believe you encoder motor is going

Any idea on cost?

I don't remember the exact cost all i remember is that it was damn expensive, like $800 expensive.

hitempguy · February 27, 2009

Truck bills '09

Whatever this encoder motor costs ~$800

New Instument cluster~$330

Repair G80 ~$600

Cigarette lighter short ~ $75

CD player quit ~?

Mark, how many miles on your truck? GM extended the warranties on the cluster in the 03/04 trucks to 75,000 miles. If you have less than 75K miles, you should have gotten this fixed for free.

125k miles. I got a recall notice when I had 90k on it and they turned me down. I have been using my GPS for speed since the speedometer was the only malfunction. Now, my oil pressure is pegged, my temp is showing 180 all day, and my tach dies after about 5 minutes.

GM has extended the warrenty on the cluster replacement. I don't think there is a mileage or year cutoff anymore. GM won a huge lawsuit against DELPHI and part of the deal was they would replace the clusters. My 04" Sierra had 130, 000 miles and it was no problem. if you already had your cluster replaced, GM will reimburse you for it.......

bobcat5544 · December 22, 2008

With out knowing the code all I can do is guess.

There are 3 things that can happen that are common. Listed in order is the most common.

1. Transfer case speed sensor harness connector. There is a TSB on this to replace the connector due to water getting into the wire harness. this problem uasaly happends during snow and rain

2. Transfer case encoder motor sensor

3. 4X4 switch