Thanks Mixman. So the SnapOn, Autel, and Thinkcar are all probably that final GM program. Not sure what is causing my issue.

Im thinking to modify my height sensor mounts by drilling the holes to be short slot so I can rotate the sensor body a bit. Just by loosening the mount screws and rotating slightly in the existing hole I was able to dial out 5/8" of the difference between driver and passenger side, so it doesnt take much of an adjustment. I think that will work fine.

 

apologies, I got slightly confused by the two threads.

Think you got lucky with the grease, my pipes exploded spectacular and loud!
Measured my airlines multiple times with a digital Vernier, they were 6mm and 8mm as are the collars.

You voltages look in range with the right slightly higher, so theoretically the AS module should calibrate. What P/No is you AS module and is it a twin compressor unit?

There are electronic difference between single and dual modules and so possibly with the software as well. If you have a twin in an 03 set-up maybe its possible to switch to a later module year to do the calibration?

MixManSC has more experience on the module programming side, he might be able to this?

 

Where are you measuring the difference at?

Keep in mind that there are other suspension parts that affect ride height, like the shocks (charged with N2) and the adjustment of the torsion bars on the front.

Neal,

 

Oceanbrave, you're right, its a 2006 twin compressor retrofitted to a 2003. So I tried what you suggested and manually selected for a 2006 H2 and got the same "Device limit exceeded" message from the calibration. Here is the ECU numbers....

 

Legerwn, you are right... lots of things at play... even if my body mounts are compressed evenly for both sides. But in the end, considering all the factors, I want the body to set level, side to side. Having the air ride gives me the ability to easily dial that in.

Im measuring right at the rear at bottom of the quarter panel to the concrete floor. Visually, that line across the bottom of the cab is what we want level.

Most often the replacement of the ride height sensors will throw things off. This is my situation. The compressor is looking for whatever the voltage was returned from the old sensors. The new ones will always be a little different, so the truck will sit differently with the new sensors.

Anyway, I did find that simply loosening the 8mm bolts on the height sensor mount and rotating the sensors with just the play in the mount holes I was able to dial the level from 1 inch down to 3/8 inch difference. I think I can just remove the sensor and use a dril to elongate the hole a bit so I have more rotation for an easy mechanical adjustment.

Certainly if mixman has solution for proper calibration with the scan tool Im very interested! Im pretty obsessive with my cars about things working the way they are supposed to.

 

So I just jumped to Page tree of this post... Does any of this apply to my 2009 with Air ride? I have a GM Tech 2 but have not gone into look at this gack. Last failure was years ago when off road. My left to right was off. Took it to the dealer and I had a leaky air bag. Sand had gotten into the Cup that the bag rests on. It wore pin hole in the bag which caused a leak. They replace the driver side bag and reset the system.

So are we talking H2's 2007 and Back?

 

ejsmall backing-up a little, ignoring the height discrepancy, does the twin unit operate normally?

The reason I ask is comparing the single and twin body-wiring diagrams there is an earth missing see "3S" below.


I can't be 100% certain, but I have a reference twin-unit here and I've drawn-out the wiring. The H2 wiring diagram I have is for an 04:-


As you can see "3S" is missing in the 04 diagram.

What does this mean?

Well the twin AS electronics monitors the combined current of the AS Relay and Exhaust Valve, the Single electronics does not have this function. So "3S" actually connects to pin 24 on the AS module might be going into an error state due to this and there may not be a DTC to cover this scenario.

You might be able to see the AS Relay and Exhaust currents (of lack of them) on your scan tool.

To get around this, on the AS unit you could try linking the ground from the earth eyelet-tag G402 to the wire going to "3S"

Don't be fooled if you measure "3S" to ground, there is a 0.15ohm resistor linking it to ground inside the module, the voltage across it is used to calculate the combined currents.

 

Wow Oceanbrave. Thats some good sleuthing. Thank you for the effort and sharing.
Everything is functioning correctly. No codes and no messages in the instrument panel.
The dual compressor is a huge upgrade over the original single. It seems quicker air up, and much quieter. I have to put my hand on the compressors to know that they're even running.
I only have use of the scan tool on the weekend as they belong to my brother in law's shop. When I get one again I'll check the voltages.
I'll be honest, I'd be very hesitant to modify the wiring. Probably just my ignorance of certainty, but that compressor cost me a thousand dollars and they are getting rare.
I wouldnt want to risk toasting it without good reason.

The specialty salvage yard who I deal with usually has several being parted out and they just told me they havent had one in a while and nothing in play. This is probably leading indicator of the H2 value curve starting upward. What was worn out or wrecked has been recycled and what is still good isnt so quickly being junked. This is my hope anyway after now having spent over $25k so far on mechanical restoration.

 

ejsmall
Apologies, puzzled by the fact that your system works and the $1k prompted me to carefully revisit the wiring. The 04 main diagram is misleading, on one hand it shows the AS Relay ground going to splice pack S413 and on the other the 16-Way connector manifest shows it going to Pin M as it should, so there's nothing to worry about wiring-wise I suspect.

However this evening I hooked up the Tech2 to my H2 and ran the Compressor Test to check the valve currents, one thing I noticed was the test would only ever run one-time. To re-run I had to switch-off, remove the key, open the door to kill the RAP then reboot the Tech2, like a kind of "Reset"

Running the Exhaust test, was similar but on the 2nd attempt gave the error "Device Control Not Allowed", once again needed to "Reset"

So I'm wondering if these same issues are causing your problems, perhaps it's worth trying the same procedure e.g. get the H2 on blocks, Reset, then try calibrating either as an 03 or 06?

Sorry to give misleading info, I only have an 05 to verify from, everything else is theoretical so I rely heavily on the diagrams, however I do have a spare Twin Unit to work with.

 

No worries Oceanbrave. I hugely appreciate your expertise and willingness to share.
So I'll try again. Maybe next weekend I'll get the scan tool again. I'll do the depressurization, then shut everything down and reset, then do the calibration.
Im very happy with how its all shaping up. Leak is stopped and after playing with the height sensors Im just 3/8 inch difference side to side, so very close.

Now back to the Jounce bumper stops!I did check oemcats. Ive actually been very lucky chasing down obsolete parts from them, but didnt get any leads on the jounce bumpers.

I did measure the jounce bump stops on mine. As stated, mine are the coil spring type jounce bumpers which came on the donor frame. They are about 5 1/8" or 130mm long and would be same 85mm diameter at the mounting cup.

So the coil type jounce is 22mm longer than the air ride jounce, which isnt much, but I also observe that the coil jounce is significantly softer. With the air ride deflated the coil type bump stop distorted and compressed down to about 2" between the mount cup rim and axle pad. Clearly not designed to take the whole truck load. My recollection is that the air ride type bump stop was stiffer and didnt collapse to this degree.

My takeaway from this is that I definitely want to obtain the correct air ride bump stops. I'd be very afraid to drive on these coil type stops if I had air ride failure. It just collapses the suspension too close and lots of stuff could get damaged.

Option 1 - Maybe we could get some swapping going on here. If people who have deleted air ride could carefully remove their jounce bump stops and sell to those who still have air ride. Then they could use the proceeds to buy the correct coil type bump stops. Im seeing the coil type (15057984) offered for ~$22 each. If someone had some real good condition air ride type I'd pay maybe $30 each plus shipping.

Option 2 - You shared an eBay link for another GM bump stop. That seller, Quirkparts, is actually a GM dealer near me. I've messaged them to see what the specs are and if other GM fitments might be similar.

Option 3 – You shared Timbren GMRH2. This is "Timbren SES" (Suspension Enhancement System). Pretty interesting line of products. I talked with their engineer. These replace the stock bump stop, but are actually designed to augment the suspension capacity. They're taller with smaller gap between the axle pad than the stock bump stop, and are engaged when the coil springs sag under load. The engineer initially said it wouldn’t work with the air suspension because it is auto leveling, but when we talked through it we agreed that it will just act like an unloaded suspension all the time and no negative effects. I actually kind of like this idea as redundancy for the aging air system. If the air ride fails I would have these to keep it from completely collapsing. They are expensive, but they give 100 day trial with full refund. I might pull the trigger and do these….. thinking…. He also said he would do a custom shorter bump stop to my specification for same price if they didn’t work well. Again, expensive for what it is, but keeping old cars going well is never cheap.

It looks like the bump stops are just pushed into the mounting cup on the frame. I see couple teeth in the cup holding them in. Probably just pull them out and hope they dont tear too much. Im going to go ahead and pull mine out as they are pretty "perished" as I think its called in Brit!