Howdy everyone. I was looking for an H3 Alpha several years ago and couldn't find a good one at a decent price. I went to look at a promising candidate - it needed some work, but I wasn't afraid of that. After driving 5 hours one way, it was in far worse shape than advertised. Dejected, I started heading home and came across the motor mile in Norman, OK. That's when I saw her. A 2003 Hummer H2, sunset orange metallic. She was calling to me! I pulled in and took her for a test spin. I was enthralled by her mix of power and size, with a nice ride, solid handling, and creature comforts! I instantly knew why these beasts have such appeal! I've put just over 50k on her since then, and I have been taking good care of her and keeping her on the road.
I have been a lurker on this site for a while, and due to a recent problem I have had with her, I thought I'd join and see if I can get some help.

 

Before going into detail on the problem, I will say that my H2 has the stock 6.0 engine and I replaced the trans, a 4L65E about 35k miles ago - it has the aluminum (vs plastic) pistons, and new "improved" servos.
My problem started with a suging/bucking action with the cruise control on. Using the throttle, it was fine. About a month later, I noticed the speedo is oscillating from 5 MPH below to 5 MPH above my actual speed. I pulled the battery and had it tested - although it would start the engine fine, it failed under a load test, so it got replaced with a new one. I thought that the current jumping around may have caused the odd issues. That apparently wasn't the issue, because not long after, the problems worsened. I have had and still have no CEL but my on old craftsman scanner I did get a P0502 at one point.

It now revs way up to 3500 to 4k RPM before kicking hard into 2nd and once she hit 3rd gear, it seems the clutch is engaging, because you can feel the trans disengage - it is not slipping. Then the speedo and odometer stopped working - all other gauges are good. I thought this was a VSS issue, so I installed a new VSS sensor - I didn't like the look of the inside of the connector, so I replaced it too. NO CHANGE. Speedo dead and no odometer movement.
Seeing many people found a shorted wire, I measured resistance to ground on the VSS connector. The green wire reads a solid short to ground and the purple was infinity. I pulled the wiring harness and did a full inspection - all is good. I pulled the ECU connectors and vetted the wires to the connector (Green side straddling the gap in the center) and ruled out a ground short. I also installed ANOTHER new VSS sensor (genuine GM part). I have checked every single fuse in the vehicle - all good.
If I kept the gear selector in 2, it seemed to work fine, but now I am questioning that as well because on a half mile test last night, it seemed I felt 2nd slipping.

So now I have questions:
I get no voltage reading to either pin of the VSS connector. Shouldn't one side have a +12 on it? Does the H2 have to be in drive for this +12 (or whatever voltage) to be applied?
Is it normal for the green vSS wire to have a ground on it?
If the VSS connectors should have a +12 (or some other dc value) then I assume the ECU applies that voltage, based on other inputs. Where does this voltage feed in to the ECU and under what conditions should it be applied?
I have ruled out an obvious wiring issue and I'm trying to rule out the ECU now.

I may be off base here and looking in the wrong areas, but it sure seems to me that the cruise control acting up, then followed by the speedo/odometer failure is not a coincidence. Knowing that the VSS goes directly to the ECU before hitting the cluster, tells me the problem is most likely in or around the ECU.
I'm almost thinking that inconsistent current or spikes could have corrupted the flash on the ECU.

My next step is to take it to a shop with a good scanner/analyzer that can command 3rd gear and TC lockup, in case I am looking at a trans problem in addition to something else. I read that in another thread here about what to look for, but I lost that thread and CANNOT FIND IT AGAIN!

Please help and thank you!

 

do you have an after market radio or alarm/ tracker that might interface with the vss signal wire like for gps? maybe it is wired improperly

 

It has the same aftermarket radio that was in it the day I bought it, 7 years ago. Never a problem until now.

 

well is it patched into your VSS signal? maybe the tape came off the wire and it is grounding out. thats why i ask. 7 years running does not automatically rule out that it failed in that area. with that logic it would mean your 20 year old truck should not be having this issue because it did bot have this issue for 20 years.
you are asking for suggestions right?

 

Welcome to HF.

 

I pulled the center dash apart and checked the wiring - the stereo is wired in using an adapter (Axxess GMOS-04) that keeps the vehicle chimes and onstar working. Shame they didn't spend a few more bucks and get the adaptor to keep the steering wheel controls. I wouldn't mind omitting the onstar, btw. The only green/white wire I see in there isn't tapped into for the stereo. The wiring job they did isn't pretty, but it isn't shoddy either. I disconnected it, just on the wild chance it was somehow causing a problem - no change.

Since I didn't find an issue in the dash (so far), I'm going to take the old VSS connector, run some extra wire to it and hook up my multimeter and run the beast down the driveway to see if the VSS sensor is generating a signal. Probably should have been one of my first steps, but I was certain I had a bad sensor, or there was a wiring problem.

 

I used the old VSS connector and ran extension wires up into the cab, so I could check for voltage while driving down the road. At approx 40MPH, I am getting 30 thousandths of a volt AC. I changed the VSS sensor and repeated - same thing. I stuck my pinky down in the VSS sensor hole and there aren't any teeth in there. I can feel that there is something on either side, about 1/8 an inch out, but it doesn't seem to have any teeth at all, so it would seem my tone wheel either blew apart or somehow is out of place. I can't imagine that the tone wheel would sit beside that sensor and generate a suitable signal - it should sit directly . There is very little info on the 4484 online and I'm not seeing much in the way of resources for ordering the tone wheel - I've only found one place so far, and they don't have any prices listed.
I pulled a sensor out of an NP271-C and the tone wheel is situated directly below the sensor, so I'm pretty sure this 4484 should be set up the same way. Now if someone else could pull their VSS sensor and do the pinky check with theirs, that would be awesome to find out I'm wrong, or to have the confirmation that my suspicion is correct. So I'm going to assume I am right, and since my beast has 152k miles on it, I'll go ahead and order a rebuild kit - new seals, gasket, bearings, chain, tone wheel, and swap out that plastic shift fork with a metal one, while I'm at it.