4WD Service light on & no 4wd

[mountainclimber]

I see that this is a much talked about topic: 4WD Service light on. So I did what I could already, but I don't see any common "next steps" from where I am at now.

I have a 2003 4.2L v6 trailblazer.

When I switch 4 wheel drive switch to anything other than 2Hi the 4WD Service light comes on. I can also tell that the 4 wheel drive isn't engaged from how it feels when I turn in a tight radius. Common problem, I know. I just don't know where to go from here.

So I tried all of these:
1) pulled fuse #8 (front box) and #45 (rear seat box) fuses for a minute.
2) disconnected the battery completely for 15 minutes
3) replaced front axle actuator

Turning the 4wd switch: 2hi to A4wd I get a lower whirring sound, A4wd to 4hi I get a quicker and louder whirring sound, 4hi to 4lo I get no sounds. (The mode lights turn on and off normally as I change mode.) I do NOT hear the "cluck" sound some people say I should hear.

Possible causes: I jumped someones car and a couple weeks later (I am guessing) my battery went dead. I replaced the battery in my car and a few days later (could have happened earlier I'm not sure) all works fine except the 4wd.

I'm thinking I need to do one of the following. Which do you think I should do? Is there an inexpensive way to do it? Are there any other tests I can perform to narrow this down?:

a) replace the Transfer Case Shift motor.

b) flash/reprogram the 4wd system

c) replace the encoder motor.

d) replace connectors and wires between various 4wd systems.

... or if you have another idea for my next step please feel free to mention it.

I am a DIY'er, mechanically minded, I know a little about cars, but I'm not a true car guys.

Thanks!

ps - just came over from trailvoy.com as suggested.

 

[The_Roadie]

Welcome! You would NEVER get competent answers to that list back at trailvoy since we all left to come here.

A very important observation is to describe what's happening on the mode control switch when you go from 2HI to A4WD mode. You say it goes on and off normally? Can you just describe the behavior exactly? And you should hear TWO noises - a high pitched one for about a second. That's the front axle actuator. And a lower and shorter duration one that's the transfer case encoder motor. I suspect you're not getting the front axle actuator.

You can get under the vehicle while somebody else runs the switch to confirm the location. The system also works with the ignition on but the engine off to make it easier to hear.

If you hear only ONE motor, we can work on troubleshooting the front axle actuator next.

Important questions: how many miles
Are you the only owner? If not, what's the history?
Has the transfer case fluid been changed religiously every 50K?

The clunk is typically reserved for going into and out of 4LO, but only if there's some residual driveline torque being stored and released. Doesn't always happen.

4HI to 4LO should make an encoder motor noise. Do youhave the tranny in NEUTRAL when you do this test? There's an interlock.

 

[mountainclimber]

Thanks for the help The_Roadie. Here is what I have:

Turning the 4wd switch:
All while in neutral and ignition turned on but engine off.

Sounds:
In all cases moving from left to right (2hi to a4wd to 4hi), except 4hi to 4lo, I hear one zip kind of sound coming from the transfer case encoder motor. (When going from 4hi to 4lo I hear a similar sound but it gives a series of different tones and it lasts longer.) In no case did I hear any obvious sounds coming from the front axle actuator. I put my hand on it as well to see if there were any vibrations, but there were none that obvious. I didn't hear two distinct sounds in any case. Sorry I have nothing to compare the pitch of the sound to so I can't say if it is high pitched or low pitched. It seems high pitched to me though.

Switch Lights:
In all cases moving from left to right (2hi to a4wd to 4hi to 4lo), the setting I moved from went solid for a moment before turning off and the 2hi going solid, then the follow occurred.
2hi to a4wd: 2hi solid, a4wd blinks, all other lights off
a4wd to 4hi: 2hi solid, 4hi blinks, all other lights off
4hi to 4lo: 2hi solid, 4lo blinks, all other lights off
(Which I would think is 'normal' if your 4wd isn't engaging, but let me know if you think otherwise. I.e. the switch seems okay.)

Miles: 127k
Ownership: I got it super cheap at about 100k because the transmission was going bad. I had a profession replace the transmission at 100k. I have no idea about the previous history. I suspect it has had very hard miles before me and its my ski machine so I do a lot of mountain passes with it.

Thanks for your help!

 

[The_Roadie]

Now THAT'S the poster child for the PERFECT and comprehensive description of the system behavior that I keep asking for. And hardly every get!

THANKS!!!!

Except for not answering my question about the transfer case fluid.

You definitely have a dead front axle actuator. Since you say you changed it, it must be in the wiring or the TCCM. I can post the pinout of the connector in case you have a meter and want to dig deeper. Where did the replacement actuator come from? Used or new? OEM or Dorman?

 

[mountainclimber]

I should be thanking you. Thanks! Sincerely, it is a big help.

Regarding the transfer case fluid, I thought stating that the transmission was replaced implied that fluid was changed at 100k miles. Wouldn't you have to change the fluid if you replaced the transmission? If not, I will change it right away.

Regarding your offer to post the pinout of the connector, I don't have a meter. All the meter tests I get come from the guys at O'Reillys or Advanced auto parts, and as far as I know they only have the basic check engine light meters (that don't tell you anything about 4wd or connectors). If you think they could help me, please post it. If not, no need I guess.

The replacement actuator came from Carquest and it was new. Sorry, I'll have to get back to you on the brand of the actuator if/when I remove it. I don't recall and I'd have to look at the housing to see.

When you say "TCCM", I assume you are referring to the Transfer Case Control Module.

I'm thinking I'll do my best to do a visual inspection on the wiring and connector and take it in if I see anything obvious (since it sounds like I can't do the wiring without a meter). If I don't see any obvious issues with the wiring, I'll replace the Transfer Case Control Module since that is one of the likely suspects. If installing the new Transfer Case Control Module doesn't help, I guess I have to bring it to my mechanic to look at it.

When I replace the TCCM I should do something like what is illustrated in this video, right?: https://www.youtube.com/watch?v=rnRKCahwU8A

All of my local parts shops won't allow me to return something that has been installed, which I can understand. I guess if it isn't the TCCM, I still have to eat that cost. Any suggestions on this issue would be fantastic.

Thanks again for your help...

 

[Robbabob]

I should be thanking you. Thanks! Sincerely, it is a big help.

Regarding the transfer case fluid, I thought stating that the transmission was replaced implied that fluid was changed at 100k miles. Wouldn't you have to change the fluid if you replaced the transmission? If not, I will change it right away.

Nothing can be assumed. Since it has a separate fill and different fluids, they didn't do it. Needs done every 50K, Auto Track II, 2 liters.

When you say "TCCM", I assume you are referring to the Transfer Case Control Module.

Correct!

Yes, quite the poster child, for sure

Edit: Welcome to the Nation!

 

[mountainclimber]

Thanks! Doing some more research on replacing the TCCM. There is a lot of mention that I will have to get it reprogrammed after I install it. Is that true?

Also, the video I posted earlier shows the wrong location for a 2003 Trailblazer. Should be under the driver's side dash.

 

[IllogicTC]

Thanks! Doing some more research on replacing the TCCM. There is a lot of mention that I will have to get it reprogrammed after I install it. Is that true?

Also, the video I posted earlier shows the wrong location for a 2003 Trailblazer. Should be under the driver's side dash.

I am under the impression that a BRAND-SPANKING-NEW unit will have to be programmed; a junkyard gem unit is ready to go. Just like a bunch of the other modules on this thing.

 

[The_Roadie]

Dormans from the aftermarket stores are plug and play.

 

[mountainclimber]

I replaced the TCCM: no change. I'll have to bring it in. It may be a while from now before I bring it in, but I'll be sure to post about what the final fix turns out to be.