: suspension air pump

07-12-13, 03:35 PM
I can remember that annoying/embarrassing air pump kicking in when starting and occasional just to let you know cheap sound coming on like you had aquariums in your truck. well lately that sound has vanished, no DIC warnings or codes, but to tell the truth I feel no difference in the suspension. Now either this super duper suspension did not work when I bought it (not surprised) or one could disconnect this aquarium pump and one would not even know the difference before and after
from northern srx previous post
There are essentially two types of load-levelling available with SRX. The standard is the nivomat system (info: http://www.cadillacfaq.com/faq/answers/nivomat.html) and MRC-equipped SRXs get a compressor-driven system.

If your compressor has stopped working, the possible problems are:

- compressor failure
- level detection failure (making the system "think" that the vehicle is level
- electrical supply failure (whether fuse or something else)

So basically this does nothing for actual ride comfort, my understanding now is its a load leveling system.

07-14-13, 11:49 AM
http://i36.photobucket.com/albums/e7/orandaberg/20130714_172754_zpse7542a42.jpg (http://s36.photobucket.com/user/orandaberg/media/20130714_172754_zpse7542a42.jpg.html)
http://i36.photobucket.com/albums/e7/orandaberg/20130714_172706_zpsf0d8e95d.jpg (http://s36.photobucket.com/user/orandaberg/media/20130714_172706_zpsf0d8e95d.jpg.html)
http://i36.photobucket.com/albums/e7/orandaberg/20130714_172654_zps6591bf1c.jpg (http://s36.photobucket.com/user/orandaberg/media/20130714_172654_zps6591bf1c.jpg.html)

Pics of the bottom of the rubber sleeves covering the rear shocks, both sides, notice the oily residue at the tears. Am I to understand these sleeves(for lack of a better word) inflate?

07-14-13, 11:54 AM
Yes. And with them ripped like that ill bet your compressor ran constantly and burned up.

07-14-13, 12:18 PM
ufff..... that means replacement shocks. Well I am pretty bored of sinking money in this 1000 dollar a pop fixes. If I happen by that junk yard in Germany I will consider at the right price to replace them. I guess I should garage the truck and save up for a trade in while the car can still hold up on 4 wheels and I can pass it on to a dealer for a trade! I could never have a clear conscious knowing I personally sold this to someone. I do not haul anything heavier then yard clipping and trash so I and not concerned with load levelling, its not effecting the ride. Odd(no not really) no DTC or light. I guess you actually have to have a load to activate the load sensor which I assume sends a signal which would activate the light if the aquarium pump does not start

07-15-13, 02:24 AM
Problem is I am not getting any DTC or warnings. If the light, DTC or DIC do come on I will be forced to fix this or I will be stuck with a trade in worth a junk yard pinto.

Electronic Suspension Control Description and Operation
Electronic Suspension Control Description

The electronic suspension control system, also known as the magneto-rheological real time damping (MRRTD) system independently controls the fluid viscosity in each of the 4 shock absorbers in order to control the vehicle ride characteristics. The electronic suspension control (ESC) system is capable of making these changes within milliseconds. The ESC system consists of the following major components:

• The electronic suspension (ESC) module
• The front/rear position sensors
• The front/rear adjustable shock absorbers
• The shock absorber electrical actuators, which are integrated within the shock absorbers
The ESC controls the damping mode selection according to the following factors:

• The vehicle speed
• The chassis pitch input
• The steering position
• The body to wheel displacement
The ESC module evaluates these inputs in order to separately control the shock absorbers, providing an enhanced ride and comfort level over the widest possible range of operating conditions.

Electronic Suspension Control Module

The electronic suspension control (ESC) module provides electronic control logic and output drive for each shock absorber. The ESC module makes decisions due to road and driving conditions based on various inputs. The ESC module receives input information by sensors that are directly connected to the ESC module or by other systems through the serial data line and uses these inputs to independently control the shock absorbers at each corner.

Electronic Suspension Control Position Sensors

The electronic suspension control (ESC) position sensors provide the ESC module with the body to wheel displacement input. The ESC module uses this and other inputs in order to control the stiffness of the shock absorber. If any body or wheel motion is detected, the ESC module will determine how soft or firm each shock absorber should be to provide the best ride. The ESC position sensors are mounted at each corner of the vehicle between the control arm and the body/frame.

Electronic Suspension Control Shock Absorber or Strut

The electronic suspension control (ESC) shock absorbers are monotube type which provide damping by increasing magnetic flux to magnetic particles to resist suspension movement. The ESC shock absorber has the capability of providing multiple modes or values of damping forces, in both compression and rebound direction. The damping forces are achieved by increasing or decreasing the magnetic flux to shock absorbers.

The front ESC actuator connector is located at the top of the shock absorber. The rear ESC actuator connector is at the top of the shock absorber.

Electronic Suspension Control Operation

The electronic suspension control (ESC) system uses the information from other systems in order to execute certain functions.

The ESC system does not have a malfunction indicator lamp, but instead uses the instrument panel cluster (IPC) for the display functions. When the ESC system detects a malfunction that sets a DTC, the ESC system sends a message on the serial data line directly or through the powertrain control module (PCM) to the IPC, which will display one of the following messages:

The SHOCKS INOPERATIVE message will only be displayed if the ESC system detects a malfunction that sets a DTC and causes the ESC system to disable all 4 shock absorbers. The ESC system will send a message on the serial data line to the IPC to display this message.

The SERVICE SUSPENSION SYSTEM message will only be displayed if the ESC system detects any malfunction that sets a DTC. The ESC system will send a message on the serial data line to the IPC to display this message.

The SPEED LIMITED message will only be displayed if the ESC system detects a malfunction that sets a DTC and causes the ESC system to disable all 4 shock absorbers. The ESC system will send a message on the serial data line to the PCM indicating that all 4 shock absorbers were disabled. The PCM then sends a message to the IPC to display this message.

The ESC module has the ability to store DTCs as current or history codes. Most ESC system malfunctions will display a message in the IPC and set a DTC. The message will remain ON until the RESET button is pressed on the driver information center (DIC). As long as the DTC is current, the message will be displayed after every ignition cycle and the RESET button must be pressed to bypass the message.

The ESC system uses an ignition cycling diagnostic approach in order to reduce the occurrence of false or intermittent DTCs that do not affect the functionality of the ESC system. This allows for the fail-soft actions to be taken whenever a malfunction condition is current, but requires the malfunction to be current for a certain number of ignition cycles before the corresponding malfunction code and message will be stored or displayed.

If the ESC detects a malfunction, the ESC system defaults with a fail-soft action. A fail-soft action refers to any specific action the ESC system takes in order to compensate for a detected malfunction. A typical ESC fail-soft action would be if the ESC system detects a malfunction with a shock absorber.
Automatic Level Control Description and Operation
The automatic level control (ALC) system maintains a desired suspension position under all types of towing, hauling, and loading conditions.

The system uses the electronic suspension control module (ESCM), ELC relay, ALC compressor assembly, air dryer, air lines, shock absorbers with integral air chambers, suspension position sensors, exhaust valve, driver information center (DIC), and the serial data circuit to perform the system functions.

When the vehicle is unloaded, the suspension is at a desired position, which is monitored by the ESCM using the position sensor signal voltage inputs. As weight is added to the vehicle, the position sensor signal voltage inputs change. When the ESCM detects a steady substantial change in the position sensor signal voltages for at least 10 seconds, it responds by commanding ON the ELC relay, which activates the compressor causing the air pressure in the shock absorber chambers to inflate. This inflation raises the vehicle to regain the desired suspension position. When weight is removed from the vehicle, the ESCM responds by commanding ON the exhaust valve causing the air pressure in the shock absorber chambers to deflate. This deflation lowers the vehicle to regain the desired suspension position.

The compressor is a positive displacement piston air pump driven by a 12-volt DC permanent magnet motor. The compressor draws filtered air through an intake line attached to an under body rail. The compressed air is then run through a dryer containing a moisture-absorbing chemical that dries the compressed air before it is sent to the shock absorber chambers. Each time the compressor is activated, the ESCM commands ON the exhaust valve for 1.5 seconds to release air from the compression chamber in the compressor’s cylinder head ensuring low motor current draw upon compressor activation. The ESCM also limits the amount of compressor run time to 255 seconds to protect the compressor components from thermal damage.

The system also performs a self test on each ignition ON cycle in which the ESCM commands the ELC relay ON, activating the compressor for 4 seconds then monitors the position sensor signal voltage inputs to verify the compressor is functioning and the system is holding air pressure.

The ESCM has the ability to detect malfunctions within the ALC system. Any malfunctions detected will cause the DIC to display the SERVICE SUSPENSION SYSTEM message. For more information on other functions of the ESCM,


Can anyone explain in layman terms how this bag works on the rear shocks, I can understand air going in chambers in the shock itself, but these outside bags?

07-15-13, 02:48 AM
I could be wrong but I believe that where the description says: "it responds by commanding ON the ELC relay, which activates the compressor causing the air pressure in the shock absorber chambers to inflate", the shock absorber chambers is referring to the outside bags and not to the shocks themselves. I say this because a number of years ago there was a company here in the US that made shocks that were height adjustable by air pressure and that is how they did it.


07-15-13, 02:36 PM
Well checked with the Junk yard in Germany and the price is 600 euros(783 dollars)for a 2007 USED pair, that is WAAYY to high for a set of shocks sure to go out in another few thousand KM. Problem is I just cannot trust this truck brand, sure enough if I invested in new shocks something will go wrong engine or drive train wise. Basically everything under(not yet the shocks or compressor or transmission) and in the engine compartment(aside from the motor has been replaced) on a car bought with under 45000 miles

07-16-13, 03:17 AM
same issue here. when my vehicle is loaded down the rear sags quite a bit now. I would also seek a do it yer self route.

07-16-13, 05:13 AM
Its a easy job, the trim panels probably would be the worst (breaking clips ect) you can change it out to non outer air bag see link above

07-16-13, 06:08 AM
Go with aftermarket struts from KYB and ditch the air ride then

I can walk you through the strut bypass if you need

07-16-13, 07:00 AM
KYB does not do rear, my struts are not a problem

07-16-13, 09:01 AM
I think if you have HID head lights you have to self leveling rear shocks so lights work property (don't blind on coming traffic etc). I believe it law in USA.

07-16-13, 01:36 PM
Strutmaters and Suncore do



07-16-13, 01:54 PM
Yes I have the link in my first post. Suncire supplies rebuilt compressor

07-16-13, 02:01 PM
Try and order it, they dont have them. Tried that when my sisters failed due to a leaking strut. We already replaced the compressor once 2 years ago so it wasnt covered on this failure either

900 for 1 strut and the compressor later the rear air ride works again. Now to just wait for the engine to stretch the timing chains hahaha

07-16-13, 02:46 PM
rockauto has rears for 430 each, but when I think about it as long as I have no heavy hauls I do not need this system? I mean I have no DTC and no light, connected a large empty trailer to it today and drove, nothing different, no sag no light. If I can keep it this way I will till I can save up for a trade in.

07-16-13, 03:44 PM
Sisters had the DTC saved for the failed compressor valve which SHOULD of gave the "Service Suspension SYS" on her nav screen but it never came up.

Only reason I found out it wasn't working was hooking up my Modis to see why the ABS and TC lights came on (steering wheel position sensor).

She had a hole in the strut which burned up the new compressor. Last compressor was replaced as it ran but the filter was so clogged no air actually went into the struts.

07-16-13, 04:25 PM
Ok so her front struts went out as opposed to my rear shocks

07-16-13, 06:33 PM
No. The rears.

07-16-13, 07:34 PM
There are no struts in the rear, just shocks, knuckles, control arms and links. In fact the SRX doesn't have struts in the front either, just steering knuckles that are often called struts by mistake, I guess.

When a suspension strut is used, it also functions as an upper control arm to locate the wheel in addition to the function of a shock. Doesn't make for the best handling suspension but its ok and saves the car company money. That's one place where GM spent a bit more money on the SRX then was absolutely necessary.


07-17-13, 01:27 PM
Now this is weird, went to the office and hooked a heavy trailer, still no code no DIC warning. Now I assume this added feature the original owner paid for is suppose to work correctly, if not a code should show or a light. So I assume its the load level switch thats out, not telling the module whats happening. Question is since its not effecting the ride and no warnings, I guess I can leave it as it is and save at least 1400 dollars or more in a new pump and shocks. Any thoughts?
Second question
Where is the fuse for the pump, the manual describes removing the filter cartridge but I see no separate part number for that?
http://i36.photobucket.com/albums/e7/orandaberg/0512136E07-020_zps4ff77d96.jpg (http://s36.photobucket.com/user/orandaberg/media/0512136E07-020_zps4ff77d96.jpg.html)

07-17-13, 01:38 PM
2 fuses, labeled ELC, 1 in RR block, 1 in LR block

07-17-13, 01:38 PM
Same difference... Generation Alternator Strut Shock, Doesnt change the fact the rear shock was fine, the air bag however used in the level function was ripped leaking air out of the system constantly running the compressor and it burned out.

07-17-13, 01:46 PM
I know there is a 4 sec start up on ignition? I thought there was a 222 sec max time so it would prevent the pump from burning up, after the 222 seconds it just would not come on till the next start?
So opinions? Leave it alone as long as I have no DTC and lights and it does not sag in the rear with a load, now I am not talking about hauling a streamliner. I just hooked up a trailer with some heavy engines in it and no sag(well when I say sag the body is not lowed down to the wheels).
Also has anyone removed the filter cartridge and cleaned it or replaced it?

07-17-13, 03:43 PM
I would say that given the costs of the shocks and the fact that your ride isn't suffering, don't bother. That said, I wouldn't load the rear suspension such that the back end drops and drive at night as your headlights might blind oncoming drivers.


07-17-13, 04:01 PM
Thanks, no problem with that,like I said I only haul grass clippings and trash to the dump, maybe some light furniture. So would one agree its probably the load level switch gone out, in regards to the pump I will look at the fuses just for a double check.

07-17-13, 04:17 PM
Hard to speculate why the pump doesn't run but given the condition of your underside, I would check for corrosion at the connectors for the pump and level control sensors after checking the fuse(s).


07-17-13, 04:30 PM
Actually I do not need the pump running considering the bags are shot, it did run before, just quit, the fuse is just for my curiosity, if its out I will leave it alone. Too much trouble to remove the hitch to bench test the pump if I am not going to replace the shocks, and yes I would not doubt the switch is corroded, I did look at them today and they did not look bad. But I think I should leave well enough alone so no light does come on or DTC when I trade in.

07-18-13, 04:45 AM
I had the same issues. I knew the shocks were shot because the ride was terrible and I didn't realize it was an active system until I got the VIN decoded. I considered going with changing over to standard shocks with bypasses (electrical, resistors to fool the monitoring system) but I was able to buy a set of shocks on Amazon (of all places) and for not much more than any of the conversion kits I could find. For me, it was a no brainer.

I bought a used air compressor that came with a 1 year warranty (which was as good as a new product) with the potential downside of having it fail and lead to bag damage and labor costs. However, the cost savings was more than half over new and still substantial over rebuilt. It was a risk I thought was reasonable and I'll just keep an eye on the system. So far, it is whisper quiet and keeps the car level with the result of having the headlights properly pointed.

If you are unsure about restoring the suspension, I can tell you the difference between not working and working is phenomenal. I can't say what it would be to go with a non-active replacement of course. Also, after I put in the replacement compressor, there was a significant improvement in the ride quality. I believe that the air suspension is baked into the system and needed for proper overall performance.

I will say, I never got any error messages, I even disconnected the front shocks and nothing. That leaves me confused. I guess I need to get to a GM dealer and let them pull the error codes from the system. Anyone have any info on the suspension diagnostic procedure? What is the most common failure that leads to a non-functioning system with no error messages. Or, since the system wasn't working properly (other than shot shocks = rough ride, I didn't know it when I bought the car - would have colored my decision), is it possible to disable the system from some central point (no bypass resistors that I can see) that would fool the system?

2005 Northstar V8 and active suspension w/ 100,000 miles

07-18-13, 10:50 PM
I am probably wrong but I do not think it has anything to do with ride comfort, the MRC does that, the bags and compressor is for load level control. I assume there are DTC if the MRC goes out. Maintenance schedules should be included in the mileage check of components for suspension

09-24-13, 06:10 PM
After much discussion via Ebay of all places (they never answered any of the emails sent to the company), Suncore has finally updated their website, you can now purchase a new non OEM replacement air compressor for 210 dollars, it says replacement now, but they have confirmed its a new one. So that radically reduces the price to replace a otherwise costly part, you can still get a OEM one for 439 dollars on http://www.gmpartsclub.com/ cheapest for OEM, but maybe Rippy can match it?

03-14-15, 07:55 AM
Hi all, after spending over an hour and half going thru posts trying to get a better understanding of the rear shocks on my 2004 Cadillac SRX Northstar 67,000 miles I still have a basic question that seems unconfirmed. If I have a small 1/2 inch hole in my rear right shock bag that I can see when I rotated tires but, the car rides fine, sits fine (no odd sag), the compressor pump goes on/off after 5 seconds after startup self check does that mean the shock is bad? Why would the compressor not continue running for a longer time if it actually sensed a loss of pressure on that one side. The car is raarely overloaded but, I have to admit, when we have had around 4 plus passengers total I remember it running for longer that 5 seconds or actually, while driving along for some time it coming on (again for longer than 5 seconds (but not necessarily 200 plus seconds indicating the system shut off protection time was reached). Thanks in advance for you help

03-15-15, 12:37 PM
Still looking for a response ... thx in advance

03-15-15, 01:08 PM
My reading of the SM says if the ride height is OK, the compressor just does a test run. The system is supposed to maintain 7-14 lb. pressure, if not the car will settle. Upon loading, the system should adjust and maintain ride height without continuous compressor running. It also mentions dust sleeves on the shocks. Sounds to me like you're OK.

03-18-15, 11:10 PM
I remember reading somewhere on here the compressor cuts off after a certain amount of time to prevent it from burning out. A set amount of seconds.