Hmmr I do apologize again, but I'm a still confused, what if this a picture of ?


Your new compressor unit, which looks great BTW, seems to be constructed from your old one, have you already wired-up the later version of connector?

If so does the later version pressure sensor physically fit into the original valve block and so it's just the connector that is different?

Anyway, below is a snippet for the 2008 AS Pressure Sensor Connector wiring taken from the GM manual.

The GM connector information above shows 0V and +5V is reversed.

The GM data should be correct, however to verify you can follow this:-

• The GM AS ECU module shown in your unit below is for a Hummer 2005, note the original module was 10363984 but yours is interchangeable being the later version.
• The wiring allocations for this module are as marked below (easy to check with a meter)
  
• This is the PCB pin assignment of the ECU module connector, so you can see where the above pin allocations come from, I have also verified the wiring on the unit I have here.
  
  
  I see you already have a bare wire poked-in the Low Ref which is correct. This actually is 0V and you should find it also connects to pins 7,8 and 20. Note that the 5V Ref is directly controlled by the AS CPU and can be switched On and Off by software, the point is you may not see +5V if you power up the unit in isolation. The 5V Ref supply also feeds the two ride-height sensors and so the combined 3 sensors are current monitored as a group by the CPU
• Based on the above, I have the wiring shown as below, I rotated your image by180 to match GMs diagram so you can follow my reasoning:-
  
  

Based on GM's drawing, confidence is high your pins 1 and 2 are swapped 🤞 but ultimately it's your call

 

Oceanbrave,

Thank you for the prompt reply, it was very helpful, the drawing from the 2008 manual was all I needed to resolve my issue.

The first photo you attached to your reply was not a valve I ever had, I think that may have been one I found for sale on eBay, it was never my valve. The solenoid valve I have as you see in my photos is a complete solenoid valve block with sensor, factory edition from Dunlop, I didn't just get the pressure sensor, I purchased the complete unit.

I fitted the new 3 pin plug onto my existing wiring harness and got pins 1 & 2 around the wrong way, it was a 50/50 bet with out the 2008 manual drawing. Thank you again, I will do the modifications on the weekend and let you know how it goes.

 

Hmmr ah I see now, the photo was in Brett Truxton post just below yours, so my mistake , so all makes sense.

The work you've done on your air suspension is most impressive and hopefully it will work as expected.

There must be a lot of H2 owners looking for a similar fix before they succumb to coil springs, the key is the valve block, how on earth did you find it?

 

Oceanbrave,

I know they still supply factory replacements so I researched the manufacturers and found Dunlop as the best choice for assistance. It did take months, nearly a year of requests for assistance, but at the end they supplied me a complete solenoid block with pressure sensor.

My first contact was the Global accounts Manager details below and then he suggested to purchase it through Miessler automotive and the contact there is Oliver Miessler o.miessler@miessler-automotive.eu


Steve Geffen
Global Account Manager
www.dunlopsystems.com
Tel: +44 (0) 2476 889920
Mobile: +44 (0) 7768 115079

 

Hmmr yours is by far the best solution I've seen so far, I can see you've put a lot of work into it and you surely deserve it to work well.

I did wonder you managed to acquire a valve-manifold and it's very kind of you to post the information, no doubt we'll all end-up needing to do the same job some day.

I too have spent a lot of time on the AS, working mainly on the electronics and wiring, although I have stripped down a valve block to service it. Also produced some AS Unit electrical diagrams and fully reverse engineered the ECU, I even managed to repair one. The one area I'm lacking is in GM software, just haven't had time to go there yet.

I did track down the P/No of the old block (88982408 or later 9331131) but it's discontinued of course ,although there were some for sale at extortionate prices, cheaper to buy a complete whole new unit.

So if you need any electrical data I may be able to help.

 

Have you tested it yet?

 

Hi Oceanbrave,

I just removed my air compressor module out and tested the wiring connections and to my surprise I have them in the correct positions. I just marked them wrong on the photo I posted. Therefore I still have a problem and I was so excited to think I was going to resolve it by simply exchanging two wires around.

My problem is the new sensor reads 35 psi always and when I start the car up the compressors run when there is no need for air because the ride height is fine so you would expect after it computes all is good it would switch off, which it does do eventually, however sometimes too late. It has burst 4 hoses exceeding the pressure rating. The blue hose supplying the inflator switch is rated at 145 psi and I have recently installed a 140 psi pressure relief valve in the line to prevent it bursting. I hear it blow off every morning 3 or 4 times before the compressors stop.

The CPU and the pressure sensor are all new, in fact everything is new expect for the wiring loom. There was one thing I picked up in your earlier post about the CPU monitoring the 3 senors as a group because my Tech 2 indicates the "Total Valve Current 0 mA" which can't be correct. Any suggestions ?

 

can you cycle the solenoid from special functions menu manually? have you been able to do a relearn?

 

Hmmr your latest results are similar to your very early posts, this seems very odd indeed (wiring?)

Of course try the "relearn" that bronxteck suggests (assumed you'd already done this) also I check there are no DTCs like C0563, C0569, C0711?

Your screen shots are very helpful, but it's difficult to pin down anything specific, however below is similar screen shot taken from my H2 (a bit blurry):-

Note two things, the "Rear Leveling Press" is 41 psi ambient (similar to your early posts, not the 15 psi we'd expect) and the "Height Sensor Current" is 21mA

Here are some observations:-

• Your ECU may interpret 35 psi as "low" so it's constantly attempting to raise the pressure, hence the hoses eventually burst (seems possible)
• The "Total Valve Current" refers the current flowing through the air solenoid valves and not the sensors. You'll see this value changes as each solenoid operates.
• It's actually the "Height Sensor Current" which is the sum of the 2 Ride-Height sensors (plus the Pressure Sensor) Each Ride-Height sensors draw between 8.5 to 9.5mA however the Pressure-Sensor only draws around 2mA (just confirmed on the bench) The combined draw seems to be around 21mA normally, so 17mA could indicate a problem with the Pressure Sensor, perhaps it's not connected properly?
• On the bench the Pressure Sensor reads 0.455V ambient, so a "Rear Leveling Air Press" of 0.22V also seems low. I suggest unplugging the Pressure Sensor and doing the following:-
  1. Continuity-check the wiring to the ECU, my post of Jan15th shows the ECU pin allocations (which are correct) however the sensor connector wiring relies on the new GM data (may be a bit of an assumption, hard to verify)
  2. Check sensor pin 3 connects only to ECI Pin 11 and no other pin! All sensor connections should read very low ohms around 0.1 - 0.2 ish.
  3. With the engine running and the sensor unplugged (see note about compressors below) monitor the "Air Leveling Press" voltage with a Tech2 as follows:-
     • With no jumpers installed the reading should be around 0V, but possibly unstable/floating.
     • With Pin 3 (Signal) shorted to Pin 1 (Low Ref) the reading should be 0V, or very close and stable.
     • With Pin 3 (Signal) shorted to Pin 2 (5V Ref) the reading should be approx 4.5V or greater and stable.

Note
If possible, run with the compressors unplugged, however the "over-temperature" inputs i.e. pin 1s may need connecting to ground (chassis) If running the compressors please be careful even with the pressure relief valve !!

If the "Air Leveling Press" readings behave properly the ECU is very likely OK, if so the Pressure Sensor could be wired incorrectly or is faulty. Don't know if a sensor could survive reverse power, not something to try.

If the readings aren't sensible it's either wiring related or the ECU (unlikely)

If I had to estimate based on the history, I'd say:

• Two ECU's with the same fault - unlikely.
• Two Pressure Sensors with the same fault - unlikely.
• Can't be the manifold otherwise the hoses wouldn't have burst.
• Possibly an issue with the sensor Signal or some other wiring anomaly.
• An issue with the new sensor wrongly connected still
• The ECU has a bad/corroded contact or a wire (Signal) or connecting/shorting to something else.
• Inspect ECU Pins 3(5V Ref) 11 (Signal) and 19 (Low Ref)

To 100% test the ECU
You could substitute the Pressure Sensor with a 2.2K linear potentiometer (signal to slider) That way you can adjust and monitor the "Rear Leveling Air Press" in real time, which would prove the ECU & wiring are OK.

To test just the sensor
I've just mounted one in a manifold, connected 5V, applied air pressure to the 8mm port (air-bag ports closed-off by default) and measured the sensor output voltage which increased with pressure just as expected. Did you keep your old one?

Really hope you get it sorted....

 

Just checked an old screenshot from my Tech2... I only have the first page though (actually two - one with the ALC active, one without).

With the ALC Exhaust Solenoid active the total valve current was 522 mA, inactive that was 0.

Right sensor - 2.59v
Left sensor - 2.41v
Height Sensor Current - 19 mA

So I'm thinking the sensor current of 17 mA "might" be okay but maybe since mine was 19 but maybe there is some threshold that 17 would be a problem. Mine was also the original single compressor style setup so there also might be some differences there as well. Just wanted to put the data points out that I had in case it might help or offer any additional insight.