: Problems with rear leveling system

09-03-09, 01:08 AM

my otherwise very reliable Omega (Catera) started giving me some problems this week.
The leveling light in my dashboard kept on blinking steadily and the rear part of the car was all the way up in the air and the rubberparts of the rear shocks were rock hard.
I removed the relais for the air compressor, but the rear still stayed up. So I disconnected an airline at the t-connection and let all the air out of the shocks. Now the rear is back to normal.
What could be wrong? Is there a valve that regulates the air going in and out of the rear shocks or is there a sensor somewhere telling the compressor when it needs to pump air?

Thanks in advance for giving me an idea what the problem might be.

Hans in Riverside, CA

2000 Catera Sport 107k miles

09-03-09, 01:46 AM
There is one sensor on the rear right control arm, also there is a valve somewhere near the compressor, I think there was a post about it and someone had found a different valve from a different car that worked and it was cheap but you will have to search for it.

Otherwise it could also be a plastic line, those get old and crack after so many years of winters and summers...

I think you can do a leak test and pressurize the system and see if you hear any hissing.

09-03-09, 09:10 PM
Hi Catera MV6,

thanks for your reply. I searched all posts for a long time, but could not find the one you mentioned.
The leveling valve costs over 400.--.

My system does NOT leak air, vice versa, the compressor
pumps the shocks up all the way and the rear stays all the way up in the air.

Is there a valve controlling the air going in and out of the rear shocks and where is it?


09-04-09, 12:49 AM
On the rear right control arm there is a sensor that tells the car how much load based on the change in angle of the control arm... if that sensor fails then it wont know when to stop so as a result it will pump up to the max and then cut out.

Check that sensor before you do anything else..
THe sensor is barely attached on there with a plastic clip and a small ball joint so if that broke the sensor wont be telling anything to the car.

Another thing is the wiring from that sensor could be broken as well.

If the system pumps it up all the way to the max then it means that its a input variable that is missing...

For example if it was leaking air the system will run all the time trying to make up for the lost air...

Does that make any sense?

09-04-09, 01:14 AM

10-10-11, 08:30 AM
Why can't a valve be inserted into the airline allowing an outside source to vary the air level when needed? I did this to an old Lincoln MarkVIII, and while it didn't last but maybe a thousand miles, the principal was sound.

10-10-11, 07:09 PM
Here's some more info from the manual.

Height Sensor Operational Check
Turn the ignition switch to the LOCK position.
Turn the ignition switch to the RUN position to reset the ALC sensor timing circuit.

Support the rear wheels or support the rear lower control arms so that the vehicle is at its normal trim height.

Raise and support the vehicle. Refer to Lifting and Jacking the Vehicle in General Information.
Disconnect the link from the ALC sensor arm. Refer to Automatic Level Control Sensor Replacement .
Ensure that the ALC sensor wiring harness connectors are secure.
Move the ALC sensor arm up. The compressor should turn on and the shock absorbers should start to inflate. Refer to Automatic Level Control System Operation Check if the compressor does not run.
Move the ALC sensor arm down until the compressor stops.
Move the ALC sensor arm below the position where the compressor stopped. The shock absorbers should deflate. Check for DTC's and/or replace the exhaust solenoid valve if the shock absorbers do not deflate.
Connect the link to the ALC sensor arm. Refer to Automatic Level Control Sensor Replacement .
Lower the vehicle.

Automatic Level Control System Operation Check
Support the rear wheels or support the rear lower control arms when certain tests require raising the vehicle on a hoist. Use two additional jack stands to support the rear lower control arms in its normal curb weight position when a frame type hoist is used. Refer to trim height specifications in Suspension General Diagnosis.

Refer to ALC Suspension System Check for electrical troubleshooting of the Automatic Level Control (ALC) system or if DTC's are present.