The driver side sensor on my 06 H2 crapped out and I replaced it. The rig would not sit level and we couldn't get the voltage to match either. After replacing the sensor the vehicle now sits level, but after sitting in the driveway for several days both airbags deflate which was not happening before replacing the left sensor.

1. Has anyone experienced this before and if so what needs to be done to correct it?
2. Is there any reason you must use a Tech 2 to calibrate? We used a good quality programming device (actually tried 2 different brands) and every time we tried to enter "calibration" mode the ECM kicked out the device
3. In the end we simply adjusted both L & R sensors to get the vehicle to a good height and laser level
4. I should also say that the H2 has a Fabtech lift kit

Any info on the right way to correct this and/or re-calibrate the system would be greatly appreciated and thanks in advance.

 

only reason to deflate is an air leak. maybe an air line or fitting got disturbed, the solenoids can also leak as do the air bags them selves.

 

The deflation problem is most probably as bronxteck mentions and not related to the sensor. I've found after working on or disturbing the AS unit, the truck seems to sag noticeably for a while, but then it improves over time. The pipes, air fittings etc will have all aged, the amazing thing it is always seems equal both sides at least it has been for me.

The ECU should be inactive when the ignition is off, otherwise battery drain would be excessive, never heard of inlet and exhaust valves operating with the ignition off.

You could try disconnecting the truck's battery for a couple of days, which should prove the point.

Regarding other diagnostic tools, it's probably not a reflection of their "quality" per-say, but more of how accurately they emulate GM protocols.

I used a Tech2 just recently to re-calibrate the ride-height settings after corrupting the AS ECU by charging my battery with it still connected.

 

Got Dish Soap?

 

Thanks for the info and feedback Gentlemen - it is greatly appreciated.

 

Yep - air leak somewhere. Only way to calibrate is with a Tech2. No other tool can properly communicate with the H2 air ride computer.

 

Thanks for the Tech 2 update - good info. I know where I can borrow one and I've decided to just replace all the air lines and the bags since mileage is 143K

Looking at the parts diagrams online I have 2 more questions.

1. I found OEM bags for about $155 ea. and then on Amazon found a pair of aftermarket bags for $190. I would assume the only way to go is OEM?
2. What about the actual air lines - can I buy the right size tubing in bulk and just swap it out? Or is OEM the only way to go?

 

Cause-and-effect and prior history may help with the analysis, for example you didn't mention if you'd worked on the AS unit beforehand, other than your sensor.

Two air bags leaking equally seems unlikely, I still have two brand new bags purchased for the same reasons, never fitted them. BTW genuine bags are $137.79 at rockuto

Soap-bubble method may help, although access is restricted and it may be hard to see, but it's worth a try, others have been successful with this technique.

"Leaks" is a much discussed topic, covered many times on this forum, so it is well worth looking through past posts, this is just one.

Personally, I'd be tempted to not buy anything at this stage, you could spend lots money and still be left with the same issues. Simply try cleaning-up the existing pipes and fittings first, Do Not be tempted to grease or oil them !!!! (they are friction-lock and will pop-out under pressure) You may need to drop the AS Unit to do it effectively, it's not a big job really.

Dirt, contamination and corrosion around the fittings tends to cause them to leak after they've been "disturbed" cleaning them will help, if it doesn't then investigate further.

BTW mine still leak, equally, and slowly, it takes a couple of weeks before it becomes noticeable, not a big deal for me.

I'm not aware of any sources for replacement inlet valves or parts, so take care of the one you have.

Please keep us posted of your progress.....

 

There are air lines and fittings on the top of the compressor shelf. If you look close you can remove the wheel house liners and spray a dish soap solution from the sides and hit all the fittings from there to try and find the leak. I did on mine. One thing - with the fittings all on the top, it is very easy to get dirt on the lines and/or in the push fittings if you remove any lines which can cause more more leaks. With those push fittings it is easy to scratch the tube end that goes in which can leak but often times a tiny leak just after changing one will go away as the o-rings in the fitting settle in. When a line is removed, on most of the fittings you can also carefully pry the upper movable part of the fitting out and get to the two o-rings in the fitting and replace them. Of course sizes are not listed anywhere so you pretty much have to remove them and then find a match for the size. I did that on a couple of mine - I have a box of hundreds of assorted o-rings. I did also replace the two lines to the bags on mine. I ordered factory replacement lines online. The factory lines are all pre-bent in the right places.

To recalibrate with a Tech2 you need a set of calibration blocks which sit on the axle. There is a problem though. I doubt anywhere has those, they were expensive, probably no longer available, and since you have a lift they would not be correct anyways.... I'll get to that.

Get OEM bags. The originals lasted 10+ years..... I did some cheap aftermarket ones once and one failed within a year.

You can still re-calibrate with a Tech2. Know what your correct height in the rear needs to be by measuring to the wheel opening on the fender or somewhere else. Then when the system is deflated for calibration jack the rear of the body up on both sides to the exact height you need on both sides. Rare to see an H2 with the air ride and lifted as Rancho and apparently Fabtech are the only two who made lift kits for the H2's that have the rear air suspension... Mine is actually smaller 2 inch custom lift with air suspension - no one even makes a levelling kit style lift for the ones with rear air suspension so I have to roll my own setup by cutting the height sensor rods on half, threading and extending them and using the Tech2 to reset things. Works great but took a good bit of fiddling to get it all just right and the button the raise the rear works just like it should too.

Yours is later so you probably have the dual compressor shelf which will probably have different part numbers for the various tubes (there are a few shorter ones as interconnects with the compressor and valve module on the compressor shelf too). Make sure of which version you have and then look at this site to find the part numbers. https://nemigaparts.com/cat_spares/epc/hummer/hm2-n/07/ The tubes are NOT imperial sizes, they are metric (in case you want to just try to source your own tubing). I'd have to dig but I have posted the size of the tubing on here before. Here is a post on when I did the custom levelling.... https://www.hummerforums.com/forum/h...ir-ride-41341/

 

Many thanks MixManSC and oceanbrave for this invaluable information. I have learned a great deal and saved a few bucks too.