Electronic Power Steering System - Variable Effort Steering Cadillac Seville V

MODEL IDENTIFICATION

MODEL IDENTIFICATION

DESCRIPTION & OPERATION

The Variable Effort Steering (VES) system, also referred to as an Magna Steer steering system, varies the effort required to turn the steering wheel. VES system provides firmer steering (road) feel at higher vehicle speeds and improves directional stability. At low speeds and during parking VES system provides maximum assist.

As vehicle speed increases, VES decreases the amount of pump pressure applied to steering gear assembly to increase steering effort and improve steering feel by use of an Electronic Brake Control Module (EBCM).

The EBCM can detect a sudden turn (such as in an evasive maneuver) through input from steering wheel position sensor, Anti-Lock Brake System (ABS), Wheel Speed Sensors (WSS) and VES actuator.

VES system consists of an EBCM, VES actuator, steering wheel position sensor and 4 WSS. EBCM receives inputs from steering wheel position sensor and 4 WSS. Based on inputs from these sensors, EBCM varies the current to the VES actuator.

If VES actuator is disconnected, full pump pressure is allowed to flow through pump's high pressure line outlet, increasing fluid pressure to the steering gear. (Scheme 1) When VES actuator is controlled by the EBCM, fluid by-passes pressure line outlet and is routed back into pump, decreasing fluid pressure to the steering gear.

If a system fault occurs, EBCM sets a Diagnostic Trouble Code (DTC). DTC can be retrieved to diagnose fault. See DIAGNOSIS & TESTING .

VES STEERING SYSTEM ELECTRICAL COMPONENT LOCATIONS

Scheme 1

PRE-DIAGNOSTICS INSPECTION

When checking potential VES system faults, check following before performing appropriate diagnostic test

1. Check wheel bearing for wear or damage causing wheels to wobble.
2. Check all VES system wiring harness connectors for proper engagement, loose wires, or terminals and/or corrosion. Check harness routing, paying particular attention to wheel speed sensor wiring harness routing.
3. Check for proper outer CV joint alignment and operation.
4. Check for proper tire wear (tread depth).
5. Always perform SYSTEM CHECK before diagnosing VES system.

If mechanical component malfunctions are present, or if failure is intermittent and not reproducible, test drive vehicle. Drive vehicle in a normal manner, with normal acceleration stopping and turning.

If vehicle test drive does not reproduce any failures, perform another test drive with an ABS stop from about 30-50 MPH on surface such as gravel. Perform sudden turns (such as evasive maneuvers). Perform SYSTEM CHECK. If ABS warning light and/or BRAKE warning light illuminates, go to appropriate ANTI-LOCK article in BRAKES.

SYSTEM CHECK

Start engine. Turn steering wheel left and then right. Wheels should turn with minimal effort. Test drive vehicle. Turn steering wheel left then right as vehicle speed increases, effort required to turn steering wheel should increase. If system does not operate as described, go to DIAGNOSTIC TESTS .

USING SCAN TOOL

Connect Tech 1 scan tool to Data Link Connector (DLC) located under left side of instrument panel. Follow scan tool manufacturer's instructions to retrieve stored DTCs.

If multiple DTCs are displayed, begin diagnosis with code that is displayed first. See DIAGNOSTIC TROUBLE CODE DEFINITIONS table. Diagnose all codes in the order displayed by Tech 1 scan tool.

DIAGNOSTIC SYSTEM CHECK

Note. For terminal and circuit identification, see WIRING DIAGRAMS . Ensure DLC connection is secure. If scan tool displays NO COMMUNICATION WITH VEHICLE, diagnose serial data line. See appropriate diagram in DATA LINK CONNECTORS article in WIRING DIAGRAMS. If scan tool does not display NO COMMUNICATION WITH VEHICLE, go to next step. Ensure EBCM is properly connected. Turn ignition on, with engine off. Connect scan tool to Data Link Connector (DLC). Using scan tool, select ABS DATA LIST. If data is being received from EBCM, go to next step. If data is not being received from EBCM. See appropriate diagram in DATA LINK CONNECTORS article in WIRING DIAGRAMS, Or appropriate BODY CONTROL MODULES article in accessories equipment. Select Magna Steer display DTC function on scan tool. If DTC C1241 is retrieved, go to DTC C1241: MAGNASTEER MALFUNCTION under DIAGNOSTIC TESTS. If no DTC is retrieved, go to POWER STEERING GEAR DIAGNOSIS article in POWER STEERING.

DIAGNOSTIC TROUBLE CODE DEFINITIONS

CLEARING DIAGNOSTIC TROUBLE CODES

Note. DTCs cannot be cleared by disconnecting EBCM or negative battery cable, or by turning ignition off. DTCs can be erased using Tech 1 scan tool or they will be erased when ignition is cycled 100 times without fault reappearing. Ignition cycle counter in EBCM will be reset to zero.

1. Connect Tech 1 scan tool. See USING TECH 1 SCAN TOOL. Before clearing DTCs, check and note current DTC data. Select DTC function and then CLEAR CODES function.
2. Verify DTCs are cleared. If other DTCs are displayed, either DTCs were not cleared or ABS/TCS/VES fault still exists. Diagnose fault and repeat procedure.

INTERMITTENTS & POOR CONNECTIONS

Circuit tests can be used to identify problems, but fault must be present during testing in order to correctly locate problem. Diagnostic procedure can help determine cause of intermittent problems in VES system components. Most intermittent problems are caused by faulty electrical connections or wiring.

When intermittent failure is encountered, check for DTCs stored in EBCM. If DTCs are found, inspect related components and circuitry for poor connections. If no DTCs are found, inspect suspect circuits as follows

1. Check for poor mating of connector halves, or terminals not fully seated in connector body (backed-out).
2. Check for improperly formed or damaged terminals. Carefully reform all connector terminals of problem circuit to increase contact tension.
3. Check for poor terminal-to-wire connection. This requires removing terminal and wire from connector body for inspection.
4. Review enhanced diagnostics information in scan tool operation manual to recreate conditions causing DTC to set. Determine how often and under what conditions fault occurs.
5. Analyze SNAPSHOT data for unusual conditions.

If inspection does not help locate intermittent problem, use self-diagnostic system to identify suspect circuit. See appropriate ANTI-LOCK article in BRAKES.

STEERING RESPONSE PROGRAMMING

1. Connect scan tool. Select MAGNA STEER and RECALIBRATION. Answer VIN question; YES if VIN is correct or NO is incorrect.
2. Answer scan tool RECAL WITH FACTORY STANDARD CALIBRATION question. YES will automatically install factory calibration. Exit scan tool. Programming is complete. NO will bring up selection menu.
3. If NO is selected in step 2) , select desired response mode from selection menu; MORE FIRM, FACTORY CALIBRATION OR LESS FIRM. Exit scan tool. Programming is complete.

DIAGNOSTIC TESTS

Note. To identify circuits and wire colors referenced in testing, see WIRING DIAGRAMS . After repairs are complete, recheck system operation to verify problem has been repaired. See DIAGNOSTIC SYSTEM CHECK . If no faults can be found, see INTERMITTENTS & POOR CONNECTIONS under DIAGNOSIS & TESTING for further diagnosis.

DTC C1241: MAGNASTEER MALFUNCTION

1. Perform DIAGNOSTIC SYSTEM CHECK before proceeding. If diagnostic system check has been performed, go to next step.
2. Inspect all related connectors and wiring for damage. If wiring or connectors are damaged, go to next step. If connectors and wiring are okay, go to step 5 .
3. Repair connectors and wiring as necessary. After repairs, go to step 15 .
4. Connect scan tool. Turn ignition on. Observe MAGNA STEER COMMANDED CURRENT and MAGNA STEER FEEDBACK CURRENT parameter in ABS/TCS ICCS (if equipped), data list. Test drive vehicle so MAGNA STEER COMMANDED CURRENT is greater than 826 milliamps. If MAGNA STEER FEEDBACK CURRENT greater than 360 milliamps, go to «INTERMITTENTS & POOR CONNECTIONS»(/cadillac/seville/v-1998-2004/remont/electronic-steering/#electronic-power-steering-system-variable-effort-steering__intermittents-poor-connections) under DIAGNOSIS & TESTING. If current is not as specified, go to next step.
5. Turn ignition off. Disconnect magna steer connector. Using a DVOM, measure resistance across actuator connector (component side). If resistance is 1.6-3.1 ohms, go to next step. If resistance is not as specified, go to step 7 .
6. Using DVOM, measure resistance between both VES control circuits for an open between VES actuator pigtail connector and variable steering actuator. If continuity exist, go to step 15 . If continuity does not exist, go to step 10 .
7. Using DVOM, measure resistance between both VES control circuits for short to each other. Measure resistance between VES actuator pigtail connector and variable steering actuator housing. If continuity exists, repair appropriate wire circuits, then go to step 15 . If continuity does not exist, go to next step.
8. Turn ignition off. Reconnect VES actuator connector. Disconnect EBCM connector. Install Pinout Box (J39700) and Cable adapter (J39700-25) to EBCM harness connector only. Using DVOM, measure resistance between pinout box terminals "B" and "C". If resistance is less than 1.6-5.0 ohms, go to next step. If resistance is not as specified, go to step 11 .
9. Using DVOM, measure resistance between both VES control circuits for short to ground or short to voltage between EBCM and VES actuator pigtail connector. If continuity exists, repair appropriate wire circuits. Go to step 15 . If continuity does not exist, go to step 14 .
10. Inspect for poor connections at harness connector of VES actuator. If poor connections exist, repair appropriate wire circuits or terminals, go to step 15 . If connections are okay, go to next step.
11. Inspect for poor connections at harness connector of EBCM. If poor connections exist, repair appropriate wire circuits or terminals, go to step 15 . If connections are okay, go to next step.
12. Inspect and repair listed conditions between EBCM and VES actuator pigtail connector in VES control circuit as follows: Open circuit wire. Infinite resistance. Short between control wire circuits. Repair appropriate wire circuits between EBCM and VES actuator pigtail connector, and go to step 15 .
13. Replace VES actuator. After repair, go to step 15 .
14. Replace EBCM. After repair, go to next step.
15. Connect scan tool. Clear DTCs. Test drive vehicle. If DTC C1241 resets, go to step 2 . If DTC C1241 does not reset, repair is complete.

POWER STEERING PUMP BELT

Note. See ADJUSTMENTS in appropriate RACK & PINION article.

STEERING EFFORT ADJUSTMENT

Note. See STEERING RESPONSE PROGRAMMING under DIAGNOSIS & TESTING.

REMOVAL & INSTALLATION

Note. If EBCM is replaced, use scan tool to calibrate Magna Steer portion of module. See STEERING RESPONSE PROGRAMMING under DIAGNOSIS & TESTING.

VARIABLE EFFORT STEERING (VES) ACTUATOR

VES actuator is located in steering gear pinion and valve assembly. See appropriate RACK & PINION article for removal and installation.

1. Disconnect negative battery cable. Remove right side lower dash insulator.
2. Remove VES control module connector. Remove VES control module from bracket by pressing in on retainer and sliding down out of bracket. To install, reverse removal procedure.

TORQUE SPECIFICATIONS

For torque specifications, see appropriate RACK & PINION article.

Electronic Steering Wiring Diagram (2000-01 Deville & Seville). Scheme 2

Electronic Steering Wiring Diagram (2000-01 Eldorado). Scheme 3

See also:
• DIAGNOSIS & TESTING
• DIAGNOSTIC TESTS
• DTC C1241: MAGNASTEER MALFUNCTION
• DIAGNOSTIC SYSTEM CHECK
• INTERMITTENTS & POOR CONNECTIONS
• STEERING RESPONSE PROGRAMMING