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Anthony, GMC Technician
Category: GM
Satisfied Customers: 11808
Experience:  GM Certified
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hummer h2 will not shift into 4 hi lock or 4 lo...switches..4x4 system

Customer Question

hummer h2 will not shift into 4 hi lock or 4 lo. No lights on the switches no matter what I press and I can't hear any sounds. Am looking to buy this and want to make sure the 4x4 system is ok. Hoping it's just a switch or something simple. Any help would be greatly appreciated.

John [email protected]
Submitted: 7 years ago.
Category: GM
Expert:  Anthony replied 7 years ago.



Which fuse was blown?

Customer: replied 7 years ago.
None were blown, swapped it just to be sure
Expert:  Anthony replied 7 years ago.
Ok, go under the hood and check the fuse marked TREC. Is it good?
Customer: replied 7 years ago.
Yes it's good
Expert:  Anthony replied 7 years ago.
And the 4WD fuse in the instrument panel fuse block is ok?
Customer: replied 7 years ago.
Yes it's ok. I replaced them both just in case it was blown, just didn't look blown.
Expert:  Anthony replied 7 years ago.
Ok, you have a voltmeter?
Customer: replied 7 years ago.
Yes. If you want email me your # XXXXX I can call you
[email protected]
Expert:  Anthony replied 7 years ago.

Cant do that, its against site rules.


Ok, with the key on, check for power to ground at both fuses. Let me know what you find.

Customer: replied 7 years ago.
Will do, back in about 1/2 hr
Expert:  Anthony replied 7 years ago.
Ok, sounds good. ill be here.
Customer: replied 7 years ago.
Well, after a 2 hours server crash of this site... ;) I can update you... I have power across both fuses.
Expert:  Anthony replied 7 years ago.

Sorry about that. I was off as well.


Ok so both fuses have power.


Does the switch have any lights whatsoever?

Customer: replied 7 years ago.
Looks like the backlight of the 4(up arrow) is lit and none of the others. It also looks like there is a status light (small round) to the far left of each button. None of those are lit now, during start up, shutdown, or when pressing them.
Expert:  Anthony replied 7 years ago.
Do you get a service 4WD message on the dash?
Customer: replied 7 years ago.
No message on the dash
Expert:  Anthony replied 7 years ago.
Ok, its most likely not mechanical. This may sound crazy but if you want to fix this yourself replace parts in this order. First replace the switches in the dash for the 4WD. If no luck replace the transfer case control module. One of them is it. Both have the same chance as being the problem. In the very worst case, the actuator on the transfer case may need replacement as well.
Customer: replied 7 years ago.
Couple questions.

1- what makes you think it's not mechanical? If it is one of the things you mentioned, could there still be a mechanical issue

2- roughly what are the costs of the three components you mentioned to have repaired

3- do you have part numbers
Expert:  Anthony replied 7 years ago.
If it was mechanical the computer would light up the service 4WD message in the cluster. I strongly believe the Transfer Case Module is the problem because of the fact that the dash isn't indicating a problem. Problem is the module and switches are like one piece even though they are in different places in the vehicle. YOu have to check with a GM Dealer near you because the price varies depending where you are. Id say your looking at about $400 in repairs maybe a hundred more or less.
Customer: replied 7 years ago.



Is there a way to check the switch and the module without buying new ones and replacing them? Continuity check or something? Was hoping maybe it was just the switch and hoping for a way to verify. Know any?

Expert:  Anthony replied 7 years ago.
The way to check the module is to rent or borrow a GM Factory level scan tool. If it communicates with the module then you can find out whats wrong based on the trouble codes it gets from the Transfer Case module. If it cant communicate with the module your looking at a bad module itself.
Customer: replied 7 years ago.

I have seen other posts on here with schemaic drawings. Do you have any of those to show me where the switch and modules are?

Expert:  Anthony replied 7 years ago.

the Switch is the buttons in the dash that you can see. The module is behind the knee bolster under the steering wheel.



Edited by Anthony on 3/1/2010 at 4:24 AM EST
Customer: replied 7 years ago.

I had the center panel off and it looks like the switches are all tied together. Do you replace the whole switch harness, or is each switch separate? If each switch is separate, I would doubt all of them would go bad.


To get to the Module, can you get to it from just taking the bottom panel off under the steering wheel or do you have to take the dash apart above the steering wheel. If so, any drawings / schematics to help with that?


If the system can't communicate with the module wouldn't it throw an error, or does only the motor itself get monitored?


Last question (maybe ;) is where is the transfer case acuator motor? Is that the motor at the transfer case with the harness of wires going into it? If the motor needs to be replaced, what would that run (parts and labor)?

Expert:  Anthony replied 7 years ago.
Ok, listen. If theXXXXXis absolutely dead and the instrument cluster is not sayingXXXXXinop. The control module is either bad or not powered up. I think you confirmed it has power with a voltmeter. To be sure, have a shop with the right tool try and communicate with the control module. When the systems are working and theXXXXXwas inop, the instrument cluster would sayXXXXXmalfunction right away. Since you dont have that going on, your transfer case module is not working if your sureXXXXXdoes not work.
Customer: replied 7 years ago.

Ok. Took it in today. They are telling me it is the "transfer case shift module". Is this the transfer case control module you were talking about or is the "shift" module something different? They are telling me it's a special order part, up to 1 week to get it (Michigan is the only place that has them), and it's $442.99 for the part and 1 HR to install and 1 HR to re-program.


Sound about right? I am not sure how they determined this, they wouldn't tell me - "the mechanic is busy" they told me. Does this sound right? I checked last night and I had power going to the transfer case control module on the orange wire so I know there is power going to the module.




Thanks for helping with this.

Expert:  Anthony replied 7 years ago.
No prob. I understand that it can be frustrating dealing with computer controlledXXXXX Just a good old shifter would be less troublesome. Yes, thats the same part I was telling you about. Let them do it and your H2 will be unstopable once again.
Customer: replied 7 years ago.

I could get the part online and a programmer for a little less than what they are going to charge me. How hard would it be to program (the VIN I am assuming) the module? In that case, I have it for the next issue I run into - as I plan to keep this vehicle for awhile.


Let me know.

Thanks again for all the advice

Expert:  Anthony replied 7 years ago.
The system that programs things like the part your replacing is not the same one sold on line. The ones on line are for tuning the engine. The one GM uses for the job you need is in the $4500 range. Let GM handle it so you have a reliable repair.