Electronic Level Control (ELC) Diagnostic Help

[rockfangd]

good news. Your getting closer. I dont believe the compressor is supposed to run when the key is off either. I would say check the pins to the relay and see if they are supposed to be 12v or ignition.

I figured the green one was the fuel pump test wire. That is another feature GM did away with by 96 on most models.

Also did you say your leveling light does work?

[guyslp]

The leveling light does work. It is the top center light on the right hand information center panel.

Here is a PDF scan of the ELC Wiring Diagram from the Service Information Manual. It should print out in readable size on 8.5x11" paper. That should help give some clarity, at least to those who can read these things a bit better than I can.

I have not tried running the rear defogger, which is on fuse 7.

Brian

[Cadillac Jim]

What I can make out of the schematic is that it is similar to that of later models except that it is autonomous, while later models are operated by the PZM or BCM. The smarts are in the ELC Height Sensor.

From what I make out of the schematic, the ELC will work EXCEPT when the key is in RUN, when it is "reset." When the height changes, there is an enabling "relay" (possibly a transistor or MOSFET) that turns ON for about 2.5 minutes. While the ELC is enabled, the ELC Height Sensor will operate either the compressor or the exhaust solenoid as required to level the rear of the car. There should be some information in the FSM on what the Reset line hot in RUN, does.

In the 1997 FSM, the ELC remains operating for about 5 minutes after the key is turned off to allow the car to level when something (a set of golf clubs is given as an example) is placed in the trunk or removed from the trunk. Or a bunch of people get in or out of the back seat.

[rockfangd]

very good info. I know the exhaust valve does because I can hear it when I have multiple people exit the car.

[Cadillac Jim]

Having the ELC work after the key is off is important. Some Devilles are often used with lots of back-seat passengers, and a Seville or other sedan or crossover can be, too. ELC is also important when lots of stuff like golf clubs or beach or picnic gear is loaded in and out of the trunk, as can happen often with lots of Cadillac owners and occasionally with any Cadillac owner.

[guyslp]

Jim,

I can see why lowering the car might be important from several perspectives once the key is off and the car is suddenly unladen. But as for elevating the car after it's off, I simply presumed that would take place when you start the car again.

Were you able to tell from the wiring diagram whether the system is supposed to be "perpetually on" for both the raising & lowering functions? The way I read it was that it should be fully on only when the key is in the "Run" position and that the exhaust function to allow the car to lower is perpetually active (or at least it is if you have a functioning battery). Am I incorrect?

Brian

Edited June 26, 2014 by guyslp

[Texas Jim]

Brian...

I am not the Jim you were referring to, but I think your understanding is correct.

All of the Cadillacs I have had, will only RAISE UP when you turn the key on.

They will GO DOWN at any time weight is taken off the rear suspension.

The other Jim...

[KHE]

Hmmm - My Fleetwood Brougham will run the level control system with the ignition off - I have not driven the car today but when I got in it to put the radar detector back on the windshield, the LEVEL RIDE light came on and the car leveled out.

[rockfangd]

weird. None of my caddys have come on to build pressure when the key is off. If it did I would be screwed with my deville because the shocks leak and the car settles. As soon as I start the car though it comes right back up

[Cadillac Jim]

I think that it depends on the model and the year. From what I could determine from the schematic on the 1989 Sedan Deville ELS, it is "on" all the time, but inactive unless there is a level change. When there is a level change, the height sensor module turns on for about 2.5 minutes. When the key is in run, it goes into a line in the schematic marked "Reset" which to me means that the ELC turns off when the key is in the RUN (on) position.

But, the logic inside the ELS sensor module is not spelled out, so I can't be sure exactly what is meant by "Reset." The FSM from which this figure came should spell that out in a dedicated section on the ELS. If you have the owner's manual, the ELS operation should be explained there, too.

[Lexy]

can you adjust hight of ELC using OBD as per manual on 1989 Cadillac Deville.

[rockfangd]

Hmm.

Not that I know of. The adjustments are at the Height control valves. There is a set bolt at each leveling valve.

What are you looking to do?

Welcome to CaddyInfo

[charles barnard]

hey all   I have an '89 brougham and want to improve the ride quality. the 'level ride' light goes on for a couple of seconds after starting, and goes on and off periodically while driving. I have nothing in the trunk. I don't think it's even working. can I replace the rear air shocks with conventional shocks?

[BodybyFisher]

You must replace them with air shocks, check monroes.  The rubber bladders on the shock become porous and leak.  Spray soapy water on them while inflated and look for bubbles.

If the compressor is bad, you could direct fill the shocks by rerouting the lines and installing a Schrader valve, unless you want to keep the car original and you would need to repair ALC pump or replace it.  You can find new pumps here

www.car-parts.com

[rockfangd]

I would bet replace the compressor and shocks= be happy for 20 more years😁.

Has worked wonders for me.

 

[sonjaab]

Have you checked the relays that are on the right side cowl area underhood under the

removable panel?  Could one of those be blown and not supplying power to the compressor?

Sorry cant post a pic cuz its too big.

 

Edited February 21, 2020 by sonjaab

[charles barnard]

thank you all for your input. I tried the simplest test and had a buddy sit on the open trunk of the car, turned on the ignition ( didn't start the car ), and the 'level ride kicked on and did it's job. so no problems there. it's just that the car doesn't seem to ride like a caddy should; I feel almost every bump and pothole on the road.

any suggestions?

[BodybyFisher]

Are you getting strut codes or messages on your dash?

Do you hear a rolling noise that could indicate a hub bearing problem?

Have you checked ball joints?

Loose or worn parts cause amplified impact to be transferred.  

Bounce each corner of the vehicle the movement should be dampened and it should not bounce up and down.  That would indicate a strut that is failing to dampen impact.  

Check control arm bushings

[BodybyFisher]

Do you know how to extract all DTC codes?, including suspension, body, not just P or powertrain codes.

You do know you can access them from the dash correct?

[rockfangd]

When weight is applied is the compressor airing up and shutting off? or is it running continuously

[dennisspeaks]

This is great information, I have a 89 Fleetwood with no problems. 

i do have a 94 Deville that I am having problems with the air assist, are the fuses in the trunk and compressor by the muffler?

 

Thanks,

 

Dennis

[rockfangd]

Should be.

Welcome to CaddyInfo

[sonjaab]

My 93 Devilles level system works when the car is off.

I just wonder if it works just because its tied into the light delay after

the key is turned off?

[rockfangd]

Does it exhaust only, or inflate as well?

It is normal for it to exhaust like a minute after shutdown

[sonjaab]

Not a clue why it runs.

BUT my climate and gas guages went dark yesterday!  BCM died?

I thought I smelled something electrical burning.

Gotta pull the glovebox and plug in my old BCM to check that this new old

replacement has failed.  (the old BCM the climate functions work but no guage display)