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07 Hummer H2 4x4 won’t shift to 4 Low not sure if this thread is in correct section.
Recently purchased my first real 4x4 online purchase so I didn’t meet previous owner an didn’t test drive before purchasing it was advertised as run an driveable.I’ve only driven it off delivery transporter then to back yard.
I found the driver side wheel speed sensor cable was cut. Thought this is why she doesn’t shift to 4 Low
4 Low Blicks 12 times then stops blacken never to shift.
Even w/ New wheel speed sensor no shift.( I believe the other front wheel sensor is intact but will check.
All this w/engine running & trans in neutral which I observed a red light come on then off at electric shifter.
Red usually is bad correct? Like maybe the Transfer case wasn’t in neutral so it was unable to shift to 4Low?
Next I was gonna check the grounds for the 4x4 electric shifting that on silverado trucks has (there’s not much of anything on Hummers but in reality it’s a chevy 2500) under the driver side frame, I didn’t see any such ground wires under the driver frame.
iirc I watched a video unrelated to this shifting issue an there where a bunch of ground wires inside front bumper.
Next I attempted to find an check the ATC fuse it’s supposed to be in main fuse block
according to this man.same man showed the ground wires under body.
Sounds kinda like an encoder motor problem. Not necessarily the motor itself; possibly only the contact assy that reports back to the ECM what gear it's in.
It's possible to replace just the "encoder" part. The "motor" hardly ever fails. You can "try" changing out just the encoder part, and odds are in your favor, you'll be good to go. Butt it's NOWHERE NEAR a guarantee.
Unfortunately (I REALLY like Torque Pro) it won't help you with this issue. The Deal is, you can take off the encoder motor assy, replace just the encoder part which has I'd guess 80% or better chances of fixing it, or buy the whole thing which is like 3 times as much $$$, and take your chances. Not gonna tell you which is "better", only, lay out your odds in front of you. Personally, I HATE laying UP UNDER my truck, with abuncha crusty million-mile **** falling all over my eyes and mouth, dinking with abuncha nasty filthy stuff in the nastiest filthiest part of my truck except MAYBE the brakes. I'd like to get it done and get me back to a great local IPA or some good bourbon, ASAP. Butt hay, PRIORITIES, right? Your choice.
May try shifting the case a bunch of times. I have had several of these where the 4wd literally was not used once ever and the motor and the Tcase shift rails were flat stuck and cycling the case through all the positions multiple times got em limbered up.
key on engine off trans in neutral foot off brake in a flat driveway . it should shift make sure it's not in a bind the red light just means it tried and didn't make the shift and generally shift back to 2 wd. shift it through all of the positions 15-30 times sometimes and it may go. If after that it still wont then change the shift encoder. Once it's replaced you need to use scan tool tool to perform a relearn so it will shift properly.
07,08 also had tons of updates on the transfer case control module it would not be first time a simple reflash fixes everything too. But its gotta go to a shop or dealer for the module updates. If you take it in for the updates have them update the ECM and TCM too many times the flash updates work hand in conjunction with the other modules.
Last edited by 01WS6/tamu; Nov 10, 2023 at 10:41 PM.
Sounds kinda like an encoder motor problem. Not necessarily the motor itself; possibly only the contact assy that reports back to the ECM what gear it's in.
It's possible to replace just the "encoder" part. The "motor" hardly ever fails. You can "try" changing out just the encoder part, and odds are in your favor, you'll be good to go. Butt it's NOWHERE NEAR a guarantee.
Unfortunately (I REALLY like Torque Pro) it won't help you with this issue. The Deal is, you can take off the encoder motor assy, replace just the encoder part which has I'd guess 80% or better chances of fixing it, or buy the whole thing which is like 3 times as much $$$, and take your chances. Not gonna tell you which is "better", only, lay out your odds in front of you. Personally, I HATE laying UP UNDER my truck, with abuncha crusty million-mile **** falling all over my eyes and mouth, dinking with abuncha nasty filthy stuff in the nastiest filthiest part of my truck except MAYBE the brakes. I'd like to get it done and get me back to a great local IPA or some good bourbon, ASAP. Butt hay, PRIORITIES, right? Your choice.
thanks for the tips on encoder wheel an yeah I hate crawling around under a dirty vehicle getting crape in my face.
guess I'll be holding off on the scanner.
thanks for the advise. I'll take a close look at the dash lights the ABS/ TCS & see if all yellow lights come on shifter when I turn the key.
Originally Posted by 01WS6/tamu
May try shifting the case a bunch of times. I have had several of these where the 4wd literally was not used once ever and the motor and the Tcase shift rails were flat stuck and cycling the case through all the positions multiple times got em limbered up.
key on engine off trans in neutral foot off brake in a flat driveway . it should shift make sure it's not in a bind the red light just means it tried and didn't make the shift and generally shift back to 2 wd. shift it through all of the positions 15-30 times sometimes and it may go. If after that it still wont then change the shift encoder. Once it's replaced you need to use scan tool tool to perform a relearn so it will shift properly.
07,08 also had tons of updates on the transfer case control module it would not be first time a simple reflash fixes everything too. But its gotta go to a shop or dealer for the module updates. If you take it in for the updates have them update the ECM and TCM too many times the flash updates work hand in conjunction with the other modules.
yes I've sean that video where the man shifts a few times. I've shifted but not as many times as you suggest will definity try it.
I feel though the previous owner did drive in mud there's mud on headliner/visor steering wheel ect. will stil try.
when I was attempting the shifts I had the transmission in neutrel but had engine running.you say engine off. I'll try that tommorow an report back.
btw do you have a silver TA an a red H2 an a bunch of other fast toys all on Ytube down in Florida?
I have yet to watch the electric shifters lights when turning the key on to confirm they all come on w/ key turn, all I’ve noticed is the top button 4hi lights up an I did see the red neutral come on then off.
I can’t say the service 4wheel drive on dash message comes on bc my dash just keeps scrolling though French/spanhish/English an I can’t select just one it just keeps scrolling.
the Hummer h2 is always in 4hi
(full time 4wheel drive)since I’m not planning on driving in mud can I drive around w/ failed encoder motor. Thanks Guys for advise.
I think the minimal part is called "range position sensor".
It's a bunch of contacts that tell the ECM which position the motor is in. The motor rotates the little shift shaft about 30° or something, between range steps. The way it fails is, the contacts go intermittent and then it can be in whatever range and the ECM won't be able to tell. That's when it throws up its hands and gives you the red light.
I don't think there's any snap rings involved butt I could be wrong. At least I don't remember any.
No relearn is required. Nothing really changes when you replace it, except now the ECM can see clearly what range it's in. The whole deal has splines with no indexing, therefore you can put it together out of phase, and it will lie to the ECM. (thanks IDIOT designer that never heard of poka-yoke) You have to be real careful to manually put the transfer case in the right range and install the new thingie in the right position, so that they agree. The transfer case has a detent like an auto trans does, and the encoder has a mark, to line them up. Pretty simple but not mistake-proof.
I think the minimal part is called "range position sensor".
It's a bunch of contacts that tell the ECM which position the motor is in. The motor rotates the little shift shaft about 30° or something, between range steps. The way it fails is, the contacts go intermittent and then it can be in whatever range and the ECM won't be able to tell. That's when it throws up its hands and gives you the red light.
I don't think there's any snap rings involved butt I could be wrong. At least I don't remember any.
No relearn is required. Nothing really changes when you replace it, except now the ECM can see clearly what range it's in. The whole deal has splines with no indexing, therefore you can put it together out of phase, and it will lie to the ECM. (thanks IDIOT designer that never heard of poka-yoke) You have to be real careful to manually put the transfer case in the right range and install the new thingie in the right position, so that they agree. The transfer case has a detent like an auto trans does, and the encoder has a mark, to line them up. Pretty simple but not mistake-proof.
this makes alot of sense gotta keep it in phase or you'll be buying the whole motor.reminds me when I fouled up my first distributor.
your saying the wheel thats faulty isn't keyed, so it's important to mark this wheel an reinstall new wheel in exact position.
the Hummer h2 is always in 4hi (full time 4wheel drive)since I’m not planning on driving in mud yet. can I drive around in 4hi w/ failed encoder motor. Thanks for advise
The motor doesn't car about the phasing; it's just a dumb motor that turns things. The parts that have to be in phase are the range shift shaft and the encoder.
If you look at the assy on rockauto or something you'll be able to see what's required.
Nov 10, 2023 | 04:34 PM
07 Hummer H2 4x4 won’t shift to 4 Low
Your choice.
