Suspension - Electronic Level Control - with Cvrss Cadillac DeVille Concours I final

DESCRIPTION

Note. Models are also equipped with Continuously Variable Road-Sensing Suspension (CVRSS). For information on CVRSS, see ELECTRONIC - CV ROAD-SENSING - CADILLAC article.

Electronic Level Control (ELC) system automatically raises or lowers rear of vehicle to correct riding height (curb height), compensating for load added to or removed from vehicle. System consists of an air compressor, air drier, exhaust solenoid valve, compressor relay, 2 position sensors, air adjustable rear shock absorbers, Road-Sensing Suspension (RSS) control module, and connecting air lines. ELC air compressor is controlled by RSS control module.

SYSTEM OPERATION

Vehicle's rear vertical height is measured by 2 position sensors. Position sensors convert rear height measurement to an analog voltage read by RSS control module. RSS control module determines if ELC system should exhaust or compress rear air adjustable shock absorbers, or if no action is required. To exhaust ELC system, RSS control module switches low-side of exhaust solenoid valve to ground. To compress ELC system, RSS control module switches low-side of compressor relay coil to ground. Air compressor is enabled only when ignition is on and is activated when a sufficient amount of weight is added to vehicle. Exhaust solenoid valve is enabled at all times and is activated when weight is removed from vehicle.

To ensure system is operating with at least minimum air pressure, an Air Replenishment Cycle (ARC) is commanded each time ignition is turned on. ARC involves the exhaust solenoid valve being energized 20 seconds after ignition is turned on, the air compressor activates 1.3 seconds after the exhaust solenoid valve is energized, the exhaust solenoid valve is de-energized .5 second after the air compressor is activated, and then the air compressor is deactivated 3.2 seconds after the exhaust solenoid valve is de-energized.

To reduce current draw during air compressor activation, RSS control module performs an air compressor head relief sequence before air compressor operation. Head relief sequence reduces air pressure in air compressor cylinder during start-up. Sequence involves the exhaust solenoid valve being energized, the air compressor activates 1.3 seconds after exhaust solenoid valve is energized, and then exhaust solenoid valve is de-energized .5 second after the air compressor is activated.

Air Adjustable Shock Absorbers

Air adjustable shock absorber is a conventional shock absorber enclosed in an air chamber, which extends when air pressure is increased in chamber. When air pressure is reduced, weight of vehicle collapses shock absorber. A minimum residual air pressure of 7 psi (.49 kg/cm 2 ) must be maintained at all times for proper operation.

Air Compressor

Air compressor, located on right rear suspension support, provides air pressure for system operation. Air compressor head contains intake and exhaust valves, and an exhaust solenoid valve that releases air from ELC system when energized.

Air Drier

Air drier, attached to air compressor output, absorbs moisture from air being delivered to air adjustable shock absorbers. Moisture is removed form air drier and returned to atmosphere when air is exhausted out of shock absorbers during lowering. Air drier contains a valve that maintains a minimum air pressure of 7-14 psi (.49-.98 kg/cm 2 ) in shock absorbers.

Compressor Relay

Compressor relay is located in trunk, in micro relay center. When compressor relay is energized, voltage is supplied to air compressor.

Exhaust Solenoid Valve

Exhaust solenoid valve, located in air compressor head assembly, exhausts air from rear shock absorbers and limits air compressor output air pressure.

Position Sensors

Position sensors are mounted on body over each rear upper control arm and links body to control arms. Position sensor supply voltage and ground are provided by Road-Sensing Suspension (RSS) control module. Position sensor supplies an analog output voltage back to RSS control module. The amount of voltage supplied back to RSS control module is based on vertical height of vehicle rear.

ELC TRIM HEIGHT

Note. This procedure requires a Tech 1 scan tool. DO NOT sit in vehicle during adjustment.

1. Connect Tech 1 scan tool to Data Link Connector (DLC) located under left side of instrument panel. Park vehicle on level surface. Close doors. Ensure vehicle is unloaded. If any codes related to rear position sensors are set, repair cause of codes before continuing. See «ELECTRONIC - CV ROAD-SENSING - CADILLAC»(/cadillac/deville-concours/i-final-1999-1999/remont/electronic-suspension/#suspension-electronic-cv-road-sensing) article.
2. Turn ignition on, with engine off. Using scan tool, monitor RSS DATA RS D13 and RS D14. If voltages are not within normal range, check for bent or disconnected rear position sensors and repair as necessary. To adjust ELC trim height, follow instructions on Tech 1 scan tool.

TROUBLE SHOOTING

If ELC system is not properly functioning and no codes are set, check the following

1. Check rear position sensors for disconnected or damaged links.
2. If air compressor operates continuously, check for a short to voltage in ELC air compressor motor circuit (Dark Green wire), or for ELC compressor relay stuck closed.
3. If air compressor will not turn on, check for ELC compressor relay stuck open.
4. If air compressor does not operate at full performance, check for a weak battery.
5. If vehicle rear is high and no road-sensing suspension codes are set, check mechanical portion of exhaust solenoid valve.
6. If ride is rough, cause may be lack of residual pressure in rear shock absorbers. Perform ELC system leak/performance test. See «ELC SYSTEM LEAK/PERFORMANCE TEST»(/cadillac/deville-concours/i-final-1999-1999/remont/electronic-suspension/#suspension-electronic-level-control-with-cvrss__elc-system-leakperformance-test) .
7. If circuit breakers are tripped, check for no head relief, a faulty air compressor motor, or short to ground in ELC air compressor motor ground circuit (Black wire). If air compressor motor is faulty, replace ELC air compressor assembly.

DIAGNOSIS & TESTING

Note. Diagnose road-sensing suspension codes before performing ELC system testing. See ELECTRONIC - CV ROAD-SENSING - CADILLAC article.

Note. For terminal and circuit identification, see WIRING DIAGRAMS .

PRE-TESTING INSPECTION

If ELC system is not properly functioning, check rear position sensors for disconnected or damaged links, and perform ELC system check. See ELC SYSTEM CHECK . ELC system remains operational for a maximum of 5 minutes after ignition is turned off. This time allows for exhaust function after a load is removed from vehicle.

ELC SYSTEM CHECK

1. Connect scan tool to Data Link connector (DLC) located under left side of instrument panel. Turn ignition on, with engine off. Clear road-sensing suspension codes. Wait 90 seconds. Display road-sensing suspension codes. If any ELC compressor relay or ELC exhaust solenoid valve codes are set, go to appropriate code for diagnosis. See «ELECTRONIC - CV ROAD-SENSING - CADILLAC»(/cadillac/deville-concours/i-final-1999-1999/remont/electronic-suspension/#suspension-electronic-cv-road-sensing) article. If no ELC compressor relay or ELC exhaust solenoid valve codes are set, go to next step.
2. If rear of vehicle is lower than normal, go to «REAR OF VEHICLE LOW»(/cadillac/deville-concours/i-final-1999-1999/remont/electronic-suspension/#suspension-electronic-level-control-with-cvrss__rear-of-vehicle-low) . If rear of vehicle is not lower than normal, go to next step.
3. If rear of vehicle is higher than normal, go to «REAR OF VEHICLE HIGH»(/cadillac/deville-concours/i-final-1999-1999/remont/electronic-suspension/#suspension-electronic-level-control-with-cvrss__rear-of-vehicle-high) . If rear of vehicle is not higher than normal, system is okay.

REAR OF VEHICLE LOW

1. Perform ELC system check. See «ELC SYSTEM CHECK»(/cadillac/deville-concours/i-final-1999-1999/remont/electronic-suspension/#suspension-electronic-level-control-with-cvrss__elc-system-check) . After performing ELC system check, go to next step.
2. Turn ignition on, with engine off. Listen for air compressor to activate. If air compressor turns on within 30 seconds, go to step 8 . If air compressor does not turn on within 30 seconds, go to next step.
3. Turn ignition off. Disconnect ELC air compressor assembly connector. Disconnect RSS control module connector. RSS control module is located in right front corner of trunk. Turn ignition on. Connect a jumper between ELC compressor relay control circuit terminal (Yellow wire) of RSS control module harness connector and ground. See «WIRING DIAGRAMS»(/cadillac/deville-concours/i-final-1999-1999/remont/electronic-suspension/#suspension-electronic-level-control-with-cvrss__wiring-diagrams) . Using DVOM, measure voltage between ELC air compressor motor circuit (Dark Green wire) of ELC air compressor assembly harness connector and ground. If voltage is 10 volts, go to next step. If voltage is not 10 volts, go to step 7 .
4. Remove jumper. Turn ignition off. Check continuity between ELC air compressor motor ground circuit (Black wire) of ELC air compressor assembly harness connector and ground. See «WIRING DIAGRAMS»(/cadillac/deville-concours/i-final-1999-1999/remont/electronic-suspension/#suspension-electronic-level-control-with-cvrss__wiring-diagrams) . If continuity exists, go to step 6 . If continuity does not exist, go to next step.
5. Turn ignition off. Check for open in Black wire. Repair as necessary. After repairs, go to step 10 .
6. Replace ELC air compressor assembly. Replace air lines. After repairs, go to step 10 .
7. Remove jumper. Turn ignition off. Check for faulty ELC compressor relay, or for an open in Dark Green wire or in Orange wire between ELC compressor relay and trunk compartment fuse block.
8. Check left and right rear position sensors for damage or disconnected links. Repair or replace as necessary. After repairs, go to step 11 . If position sensors and links are okay, go to next step.
9. Perform ELC system leak/performance test. See «ELC SYSTEM LEAK/PERFORMANCE TEST»(/cadillac/deville-concours/i-final-1999-1999/remont/electronic-suspension/#suspension-electronic-level-control-with-cvrss__elc-system-leakperformance-test) . If any leaks were found and repaired, go to step 11 . If no leaks were found, go to next step.
10. Turn ignition off. Connect scan tool to Data Link Connector (DLC) located under left side of instrument panel. Turn ignition on, with engine off. Perform ELC trim height adjustment. See «ELC TRIM HEIGHT»(/cadillac/deville-concours/i-final-1999-1999/remont/electronic-suspension/#suspension-electronic-level-control-with-cvrss__elc-trim-height) under ADJUSTMENTS. After repairs, go to next step.
11. Reconnect all connectors. Clear road-sensing suspension codes. Wait 5 minutes. If rear of vehicle is level, system is okay.

REAR OF VEHICLE HIGH

1. Perform ELC system check. See «ELC SYSTEM CHECK»(/cadillac/deville-concours/i-final-1999-1999/remont/electronic-suspension/#suspension-electronic-level-control-with-cvrss__elc-system-check) . After performing ELC system check, go to next step.
2. Turn ignition on, with engine off. Listen for air compressor to activate. If air compressor runs for more than 5 minutes, go to next step. If air compressor does not run for more than 5 minutes, go to step 6 .
3. Turn ignition off. Remove ELC compressor relay located in trunk, in micro relay center. Turn ignition on, with engine off. If air compressor is running, go to next step. If air compressor is not running, go to step 5 .
4. Turn ignition off. Reinstall ELC compressor relay. Repair short to voltage in ELC air compressor motor circuit (Dark Green wire). After repairs, go to step 12 .
5. Turn ignition off. Replace ELC compressor relay. After repairs, go to step 12 .
6. Check left and right rear position sensors for damage or disconnected links. Repair or replace as necessary. After repairs, go to step 12 . If position sensors and links are okay, go to next step.
7. Remove ELC intake air filter from vehicle body (DO NOT remove intake air filter from air compressor or hose). Using scan tool, select RSS OUTPUTS, and then RS 006 (ELC COMP). Cycle air compressor. After one minute, stop cycling air compressor. Using scan tool, select RSS OUTPUTS, and then RS 007 (ELC EXH). Cycle exhaust solenoid valve while checking if air is exiting ELC intake air filter. If air is exiting from intake air filter, go to step 10 . If air is not exiting from intake air filter, go to next step.
8. Stop cycling exhaust solenoid valve. Disconnect air lines from both rear shock absorbers. Connect Pressure Gauge (J 22124-B) between right and left rear air lines. Open pressure gauge toggle valve. Disconnect air line from ELC air drier. Apply shop air to pressure gauge schrader valve. If air is exiting both air lines at air drier connection, go to next step. If air is not exiting both air lines at air drier connection, go to step 11 .
9. Turn ignition off. Replace ELC air compressor assembly. Install ELC intake air filter from vehicle body. After repairs, go to step 12 .
10. Turn ignition off. Connect scan tool to Data Link Connector (DLC) located under left side of instrument panel. Turn ignition on, with engine off. Perform ELC trim height adjustment. See «ELC TRIM HEIGHT»(/cadillac/deville-concours/i-final-1999-1999/remont/electronic-suspension/#suspension-electronic-level-control-with-cvrss__elc-trim-height) under ADJUSTMENTS. After repairs, go to step 12 .
11. Replace air lines from air drier to both rear shock absorbers. After repairs, go to next step.
12. Turn ignition off. Turn ignition on, with engine off. Wait for 5 minutes. If rear of vehicle is level, system is okay.

ELC SYSTEM LEAK/PERFORMANCE TEST

1. If ELC air compressor assembly and air lines have been replaced, go to step 7 . If ELC air compressor assembly and air lines have not been replaced, go to next step.
2. Raise and support vehicle. Check air lines from air drier to both rear shock absorbers. Check air line connection at air drier. If air lines are damaged or disconnected, go to step 13 . If air lines are okay, go to next step.
3. Squeeze middle of left rear shock absorber sleeve. If sleeve can be slightly compressed, go to step 5 . If sleeve can not be compressed, go to next step.
4. Turn ignition off. Connect scan tool to Data Link Connector (DLC) under left side of instrument panel. Turn ignition on, with engine off. Using scan tool, select RSS OUTPUTS, and then RS 006 (ELC COMP). Cycle air compressor. Operate air compressor for 60 seconds. Using a soap and water solution, check air line connection at air drier for leaks. If leaks are found and repaired, go to step 16 . If no leaks are found, go to next step.
5. Turn ignition off. Disconnect air line from air drier. Connect Pressure Gauge (J 22124-B) to air drier. Close pressure gauge toggle valve. Disconnect RSS control module connector. RSS control module is located in right front corner of trunk. Turn ignition on, with engine off. Connect a jumper between ELC compressor relay control circuit terminal (Yellow wire) of RSS control module harness connector and ground. Air compressor should activate. If pressure builds to 80 psi (5.6 kg/cm 2 ), go to next step. If pressure does not build to 80 psi (5.6 kg/cm 2 ), go to step 10 .
6. When pressure builds to 80 psi (5.6 kg/cm 2 ) remove jumper to turn air compressor off. Monitor pressure gauge for one minute. If pressure leaks down, go to step 10 . If pressure does not leak down, go to next step.
7. Connect pressure gauge to right rear shock absorber. Pressure gauge toggle valve should be positioned on side away from shock absorber. Close pressure gauge toggle valve. Apply shop air into pressure gauge schrader valve until pressure gauge indicates 80 psi (5.6 kg/cm 2 ). Monitor pressure gauge for one minute. If pressure leaks down, go to step 11 . If pressure does not leak down, go to next step.
8. Slowly open pressure gauge toggle valve to release air pressure. Disconnect pressure gauge from right rear shock absorber. Connect pressure gauge to left rear shock absorber. Pressure gauge toggle valve should be positioned on side away from shock absorber. Close pressure gauge toggle valve. Apply shop air into pressure gauge schrader valve until pressure gauge indicates 80 psi (5.6 kg/cm 2 ). Monitor pressure gauge for one minute. If pressure leaks down, go to step 12 . If pressure does not leak down, go to next step.
9. Slowly open pressure gauge toggle valve to release air pressure. Disconnect pressure gauge from left rear shock absorber. Connect pressure gauge to left and right rear air line connections. Reconnect air line to air drier. Open pressure gauge toggle valve. Apply shop air into pressure gauge schrader valve until pressure gauge indicates 80 psi (5.6 kg/cm 2 ). Monitor pressure gauge for one minute. If pressure leaks down, go to step 14 . If pressure does not leak down, go to step 19 .
10. Replace ELC air compressor assembly. Replace air lines. After repairs, go to step 19 .
11. Slowly open pressure gauge toggle valve to release air pressure. Replace right rear shock absorber. Reconnect all air lines. After repairs, go to step 19 .
12. Slowly open pressure gauge toggle valve to release air pressure. Replace left rear shock absorber. Reconnect all air lines. After repairs, go to step 19 .
13. If any air lines are damaged, go to next step. If air lines are okay, go to step 18 .
14. Replace air line from air drier to rear shock absorbers. After repairs, go to next step.
15. Remove air drier from ELC air compressor assembly. With head-connection end down, shake air drier. If water/moisture comes out of air drier when shaken, go to next step. If water/moisture does not come out of air drier when shaken, go to step 17 .
16. Replace air drier. After repairs, go to next step.
17. Replace air compressor head. After repairs, go to next step.
18. Install ELC air compressor assembly onto vehicle. Reconnect all air lines. After repairs, go to next step.
19. Turn ignition off. Reinstall/reconnect all components/connectors. Turn ignition on, with engine off. Clear road-sensing suspension codes. Wait 5 minutes. If rear of vehicle is level, system is okay.

REMOVAL & INSTALLATION

Removal

1. Raise and support vehicle. Remove and support exhaust system from rear hangers. Clean air compressor surrounding area to prevent dirt from entering ELC system. Disconnect air line from air drier. Disconnect air line and 2 clips from air compressor bracket.
2. Remove intake air filter and air line from vehicle and air compressor. Disconnect air compressor electrical connector. Remove air compressor bracket-to-suspension mounting bolts. Remove air compressor and bracket from rear of vehicle as an assembly. Remove bracket from air compressor.

Installation

To install, reverse removal procedure. Tighten bolts to specification. See TORQUE SPECIFICATIONS table. Turn ignition on and wait 45 seconds. ELC system will perform an air replenishment cycle.

Disconnect air drier from air compressor by rotating spring clip 90 degrees and pulling drier and "O" ring from compressor head assembly. (Scheme 21)

Lubricate "O" ring and install on air drier. Install retainer spring to its original position. Install air drier on air compressor. Rotate spring clip 90 degrees to lock air drier in place. Turn ignition on and wait 45 seconds. ELC system will perform an air replenishment cycle.

Scheme 21

1. Remove air drier. See «AIR DRIER»(/cadillac/deville-concours/i-final-1999-1999/remont/electronic-suspension/#suspension-electronic-level-control-with-cvrss). Disconnect air compressor motor electrical wires from harness connector. (Scheme 22) Remove 3 air compressor head mounting bolts. Remove air compressor head from air compressor. Remove gasket.
2. To install, reverse removal procedure. Install NEW gasket. Tighten compressor head bolts to specification and in sequence. (Scheme 22) See «TORQUE SPECIFICATIONS»(/cadillac/deville-concours/i-final-1999-1999/remont/electronic-suspension/#suspension-electronic-level-control-with-cvrss) table.

Scheme 22

Exhaust solenoid valve is an integral of air compressor head. Exhaust solenoid valve can not be serviced separately. Complete replacement of air compressor head is necessary. See AIR COMPRESSOR HEAD .

Removal & Installation (Rear)

Raise and support vehicle. Remove wheel. Disconnect sensor electrical connector. Remove sensor harness clips from vehicle. Disconnect sensor link from ball stud. Remove screws and position sensor. To install, reverse removal procedure. Tighten screws to 11 ft. lbs. (15 N.m). Adjust ELC trim height. See ELC TRIM HEIGHT under ADJUSTMENTS.

TORQUE SPECIFICATIONS

TORQUE SPECIFICATIONS

WIRING DIAGRAMS

Note. In addition to ELC system, models are also equipped with Continuously Variable Road-Sensing Suspension (CVRSS). For wiring diagrams, see ELECTRONIC - CV ROAD-SENSING - CADILLAC article.

See also:
• ELECTRONIC - CV ROAD-SENSING - CADILLAC
• COMPUTER RELEARN PROCEDURES - GENERAL MOTORS CORP.
• ELC SYSTEM LEAK/PERFORMANCE TEST
• WIRING DIAGRAMS
• ELC SYSTEM CHECK
• REAR OF VEHICLE LOW
• REAR OF VEHICLE HIGH
• ELC TRIM HEIGHT
• TORQUE SPECIFICATIONS