Cadillac SRX First Generation Forum - 2004 - 2009 Discussion, suspension air pump in Cadillac SRX Forums; I can remember that annoying/embarrassing air pump kicking in when starting and occasional just to let you know cheap sound ...
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 http://www.strutmasters.com/Cadillac.../cad-srx-f.htm
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.
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
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:
• SHOCKS INOPERATIVE
• SERVICE SUSPENSION SYSTEM
• SPEED LIMITED
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?
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.
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