ELECTRONIC/AUTOMATIC LEVEL CONTROL RELAY

[DJRATEDR]

MY E.L.S. HAS JUST RECENTLY GONE OUT. CHECKED THE COMPRESSOR (NO POWER TO IT), POWERS UP WHEN I APPLY 12V, CHECKED THE RIDE HEIGHT SENSOR (NO POWER TO IT, E.L.S. FUSE IN TRUNK IS GOOD .... MUST BE THE RELAY - WHERE IS IT???

I FOUND THAT THERE ARE A TON OF RELAYS ON THE OPPOSITE SIDE OF THE PANEL WHERE THE REAR FUSE COMPARTMENT IS, BUT I HAVE NO IDEA WHICH RELAY COULD CONTROL THE E.L.S.

I ALSO HAVE THE ABS/TRACTION CONTROL LIGHTS ON DISPLAY. I HEAR IT IS THE SPEED SENSORS (REAR ONES ARE USUALLY SUSPECT). ANY IDEA WHERE THEY ARE AND HOW TO CHECK THEM?

YOUR HELP WOULD BE APPRECIATED,

REGGIE

[Cadillac Jim]

Do you have the diagnostic trouble codes (DTCs)? If not, please get them and post them here and we can be a lot more helpful.

http://www.caddyinfo.com/readingcodes.html

From the 1997 FSM for E/K bodies (which is probably accurate for the 1998 DeVille), they have a set of checks for when no DTCs are present:

NOTE: For all of the following complaints, check the rear CVRSS position sensors for disconnected or damaged links.

1. If the ELC air compressor is operating continuously, check the following: A short to voltage on CKT 322; ELC compressor relay stuck closed.
2. If the ELC air compressor will not turn on, check the ELC compressor relay (!!!) for a stuck open condition.
3. If the vehicle's rear is high and there are no CVRSS codes, the mechanical portion of the exhaust solenoid could be nonfunctional.
4. Rough ride -- lack of residual pressure in rear shock absorbers. Perform "ELC System Leak/Performance Test."
5. Tripped circuit breakers could be caused by the following: No head relief, check for CVRSS codes; faulty air compressor motor, replace the ELC air compressor; short to ground in circuit 1340B.

The ELC System Checks on page 3D1-5 and subsequent pages all begin with

[!]Important

Diagnose CVRSS codes first.

So, I won't go through them.

The ELC Compressor Relay is in the trunk compartment #2 micro relay center. The position sensors are mounted on the body above the upper control arms of the rear axle. Each side has a link to an upper control arm. The CVRSS control module supplies 8 volts to the position sensors.

[DJRATEDR]

I CHECKED THE POWER TO THE COMPRESSOR AND HEIGHT SENSOR (LEVEL CONTROL BOX). NO POWER TO EITHER ONE. I DID FIND THE RELAY CENTER, BUT THERE ARE ABOUT 8 RELAYS IN COMPARTMENT #2. DO YOU KNOW WHICH ONE IS THE ONE THAT CONTROLS THE E.L.S.?

CURENTLY I HAVE THE COMPRESSOR HOOKED UP TO A TOGGLE SWITCH INSIDE THE CAR SO I CAN RAISE IT AS NEEDED. WOULD YOU HAPPEN TO KNOW EXACTLY WHERE THE SPEED SENSORS ARE (REAR).

I'LL HAVE TO POST THE DTC CODES LATER. LAST TIME I CHECKED I HAD QUITE A FEW AND RESET THEM, BUT THE 2 THAT STAYED ON WERE C1234 & C1235. I'M SURE I HAVE MORE NOW, DUE TO THE COMPRESSOR - I'LL POST THEM TONIGHT.

OH YEAH, MY VEHICLE DOESN'T HAVE R.S.S. (ONLY DEVILLE CONCOURS).

[Cadillac Jim]

# C1234 - Left Rear Wheel Speed Circuit Open or Shorted

# C1235 - Right Rear Wheel Speed Circuit Open or Shorted

The wheel speed sensor (WSS) is mounted to the wheel bearing assembly near the rotation center. The cable connects to the bottom of the WSS and is routed on the top rear of the lower control arm.

You hae circuits 883 (RR WSS) and 884 (LR WSS) to check. The WSS itself should have a resistance of 850 ohms to 1350 ohms. The cables go through connector C412, feedthroughP400, connector C207, and feedthrough P100 on their way to the EBTCM. The EBTCM is mounted to the brake pressure modulator valve (BPMV) which is the heart of the ABS system. It's mounted with its pump under the hood on the driver's side, on the chassis near the right front wheel.

Sounds like a wiring problem to me. I would check the resistances of each WSS. When you find that problem, you will likely clear up the leveling system problem too.

[DJRATEDR]

YOU THINK THE ABS/TRACTION HAS SOMETHING TO DO WITH THE E.L.C.??? IT WAS WORKING FINE BEFORE AND I HAD THE "ABS & TRACTION" LIGHTS DISPLAYED. I HAD HIT A CURB WHEN WE HAD THAT HEAVY RAIN (PASS. SIDE). COULD'VE JARRED SOMETHING LOOSE OR CAUSED SOMETHING TO SHORT OUT.

NO IDEA WHERE THAT ONE RELAY IS - HUH? MAY I ASK WHAT MANUAL YOU'RE GETTING YOUR INFO FROM. I HAVE A DUMB OLE HAYNES MANUAL FROM ADVANCE AUTO PARTS THAT BARELY TELLS ME CRAP. SOUNDS LIKE YOU HAVE THE BIBLE OF CADI' BOOKS.

IF I SEND YOU MY E-MAIL ADDRESS, WOULD YOU BE ABLE TO E-MAIL ME SOME PICS THAT MAY HELP ME OUT? I'M A WHIZ AT ELECTRONICS AND AM VERY MECHANICAL AS WELL, HOWEVER, I HAVEN'T GOT THE RESOURCES YOU HAVE. I HAD AN IDEA TO JUST PUT A 1K RESISTOR IN THE W.S.S. PLUG TO FOOL THE CPU INTO THINKING ALL WAS OKAY. I HEARD THAT WILL ENABLE ME TO GET MY 1ST GEAR BACK (LOOSE 1ST WHEN TRACTION IS DIABLED - SO I HEARD?).

[Cadillac Jim]

You got me. I'm using the 1997 Factory Shop Manual (FSM). You can get yours from the OEM; look on the how-to pages of this forum for different ways. Here is a link to that page:

http://www.caddyinfo.com/shopmanual.htm

There are several books for our year models. The minimum is Volumes I and II of the EK Service Manual. You can decide if you want the transmission overhaul manual, emissions diangosis manual, etc. I bought them but haven't used them yet and hope I never need to. But, they're on the shelf in case that day comes, and then I don't care how hard they are to get or what they cost because they are there for me.

My last post addressed the codes C1234 and C1235, which indicates to me that the speed sensors to the rear wheels are disconnected. This means that a cable is disconnected or broken. Your symptoms of no volts to the ELC pump tells me that either a cable is disconnected, the module that controls them is broken, or both. I would bet on a simple wiring problem. If you hit a curb, look at the wiring and sensors on both wheels on that side, and follow the cables. The simplest thing to do is to fix all the wiring problems and clear the codes. If you start bypassing the modules with toggle switches and fooling the modules with resistors, you might as well just put tape over the DIC, throw away the fuel injection and put a carburetor on it -- except that the distributor is software in the PCM module...

The ABS, Stabiltrac, road sensing ride control, and traction control are all interrelated and use mostly the same sensors. Proper operation of these is necessary for the powertrain control module (PCM) to allow the engine to perform normally. The transmission is electronically controlled by the PCM and again the ABS, Stabilitrac, road sensing, and traction control sensors are needed for the PCM to allow the transmission to operate normally.

You can post codes here and knowledgeable people will help you diagnose and fix your car. If you start disconnecting things and putting in manual overrides, nobody can help you much.

[Cadillac Jim]

NO IDEA WHERE THAT ONE RELAY IS - HUH?

In post number 2, I pointed out that the ELC Compressor Relay is in the trunk compartment #2 micro relay center. It's accessable from the trunk. It's behind the seat on the passenger side. It has the radio, the phone (if any), OnStar equipment (if any), the chassis control module, a relay bank, and a fuse bank.

[DJRATEDR]

I HEAR YA ON THE RIGGING PART .... IT'S JUST TEMPORARY TIL I GET MY AFTERMARKET STRUTS (BYPASSING THE AIR ASSIST STRUTS AND GOING WITH THE CONVERSIONS FROM STRUTMASTERS). I JUST CAN'T FIND THAT RELAY. LIKE I SAID, THERE'S POWER TO THE FUSE, BUT NONE TO THE COMPONENTS. THE WIRES FROM THE ELC FUSE HEAD TOWARDS THE FRONT OF THE CAR AND NOT TOWARDS THE RELAY PACKS.

AS FAR AS THE RESISTORS ON THE WSS .... I JUST WANTED MY 1ST GEAR BACK SO I'M NOT CONSUMING AS MUCH GAS ON MY TAKE OFFS. I WILL GET IT ALL TAKEN CARE OF EVENTUALLY. JUST TRYING TO SAVE A BUCK OR TWO IN THE MEANTIME.

I'M GONNA GO OUT AND GET THESE CODES AND I'LL POST THEM FOR YOU IN A BIT.

YOU'VE BEEN A GREAT HELP SO FAR .... THANKS!!!!!!

[Cadillac Jim]

[attachmentid=2764] This is the circuit diagram of the ELS. It shows the relay to be "Relay A" in the relay center, which should be next to the fuse block where the ELS fuse is.

JUST CHECKED MY CODES, HERE THEY ARE:

PCM: P0741 (HISTORY)

IPC: B1552 (HISTORY)

TCS: C1234 (CURRENT)

C1235 (CURRENT)

From links on the "How To" page here, these are

P0741 - TCC System Stuck Off

B1552 - Keep Alive Memory (KAM) Error

# C1234 - Left Rear Wheel Speed Circuit Open or Shorted

# C1235 - Right Rear Wheel Speed Circuit Open or Shorted

The TCC is the Torque Converter Clutch; the P0741 code says that it wasn't clutching 4th gear to direct drive above 40 mph, probably because of one of the other problems. The B1552 error probably was caused by disconnecting the battery less than five minutes after shutting off the key, and can probably be ignored. The other two tell us that your wheel speed sensors on the rear are disconnected.

It seems that we are back to looing for a wiring problem between the module and the rear wheels.

[DJRATEDR]

THIS MAY BE A DUMB QUESTION, BUT .... AS LONG AS THE CODES SAY "HISTORY", THERE'S NO NEED TO REALLY STRESS THEM - RIGHT? "CURRENT" ARE THE PROBLEMS THE CAR HAS AT THE MOMENT - RIGHT? SOMETIMES MY KEYLESS ENTRY (INTERIOR LIGHTS WHEN I OPEN THE DOOR) DOESN'T WORK UNTIL AFTER I GET IN THE CAR AND TURN THE KEY OR START THE CAR, THEN IT'S BACK TO NORMAL.

I NOTICE IT ACTS UP ONCE IT STARTS GETTING A LIL' CHILLY OUTSIDE IN THE EVENINGS. I'M THINKING MAYBE CONDENSATION OR SOMETHING .... ANY IDEA? I DID NOTICE A LIL' WATER IN THE SPARE TIRE WELL.

YOU'VE BEEN A BIG HELP!!!!

THANKS A BUNCH,

REG

P.S. I'LL POST MY FIXES, IN CASE ANYONE ELSE HAS THE SAME PROBLEMS - GIMME A DAY OR TWO.

[Cadillac Jim]

[attachmentid=2765]

The attached file is the diagram of the electrical equipment behind the back seat fo the 1997 Eldorado, Seville, and DeVille from the FSM page 8A-201-41. It doesn't show the phone or OnStar equipment; these are in another manual. The ELS relay is in Relay Center #2, relay A.

A DTC is flagged as History if it was detected in the last 50 times you drove the car, but not since you last started it. When you check the codes with the key on, engine off, you will get codes for problems detected the last time it was driven as Current.

A history code can indicate an intermittent problem or an ongoing problem. For example, if the VSS isn't working but you aren't driving fast enough to invoke the error, the error will show as a history code.

What I would suggest is that you clear the errors causing the current codes and reset the codes and drive it, then check the codes again to see if anything is still wrong. Repeat until you have all the codes that come back every time you drive the car.