Steering System - Variable Effort Cadillac Fleetwood II

DESCRIPTION & OPERATION

Variable Effort Steering (VES) system increases steering effort as vehicle speed increases, resulting in a firmer steering feel (road feel) and improved directional stability. System increases steering effort by decreasing amount of power steering fluid pressure applied to the steering gear. As a safety feature, the system allows full power steering assist during sudden turns, such as in an evasive maneuver.

Central Control Module (CCM) cycles VES actuator on and off based on vehicle speed input from Powertrain Control Module (PCM), and sudden turn input from steering wheel speed sensor. When VES actuator is off (de-energized), full pump pressure is allowed to flow through high-pressure line, increasing fluid pressure to the steering gear. (Scheme 1) When VES actuator is on (energized), fluid by-passes pressure line outlet and is routed back into pump, decreasing fluid pressure to the steering gear.

If a system fault occurs, CCM sets a Diagnostic Trouble Code (DTC) that can be retrieved from CCM memory and used to diagnose faults. See SELF-DIAGNOSTICS .

ELECTRICAL COMPONENT LOCATIONS

Scheme 1

TROUBLE SHOOTING

Refer to TROUBLE SHOOTING - BASIC PROCEDURES article in the GENERAL TROUBLE SHOOTING section.

HYDRAULIC SYSTEM BLEEDING

Note. If air was introduced into hydraulic system during servicing, bleed system. Aerated fluid, which appears Light Tan in color, results in poor steering performance and will cause pump damage.

1. Turn ignition off. Raise and support front of vehicle with wheels off of ground. Turn wheels fully to left. Add fluid to bring level to FULL COLD mark on dipstick. DO NOT install reservoir cap. Turn wheels from left stop to right stop at least 20 times while an assistant monitors fluid level (add fluid as necessary to maintain level at FULL COLD mark).
2. If reservoir overflows while turning wheel, air is trapped in system; check for leaks such as loose connections. If reservoir does not overflow, start engine. With engine idling, add fluid to bring level to FULL COLD mark. Return wheels to center position.
3. Lower vehicle. Continue to run engine for 2 minutes. Road test vehicle. Check for leaks. Ensure fluid level is at FULL HOT mark when fluid is stabilized at operating temperature.

POWER STEERING PUMP BELT

Note. See STEERING SYSTEM - POWER article in the STEERING section.

DIAGNOSTIC PROCEDURE (SYSTEM CHECK)

Note. For diagnosis by symptom, see FULL ASSIST (EASY STEERING) AT ALL TIMES or DECREASED ASSIST (HARD STEERING) AT ALL TIMES under TESTING.

Preliminary Check

1. A short to battery voltage in White wire between CCM and VES actuator will NOT drive the actuator pintle out (assist will NOT decrease). If this condition occurs, the CCM detects this fault, disables ground side of VES actuator (Brown wire circuit) and sets CCM DTC 27.
2. Disconnect steering wheel speed sensor connector. Check resistance between the following terminals of steering wheel speed sensor connector. Replace steering wheel speed sensor if resistance is not as specified: Red and Black wire terminals - 8000-15,000 ohms. Red and Light Brown wire terminals - 500-16,000 ohms. Light Brown and Black wire terminals - 500-16,000 ohms.
3. If steering wheel speed sensor is defective, or if sensor circuit is open, shorted to battery or shorted to ground, CCM DTC 44 or 45 will set. Although a wire may test okay when checking voltage or continuity, a broken (or partially broken) wire inside of the insulation could cause a fault.
4. To accurately check for an intermittent break, check for a voltage drop in the wire (under load). Ensure aftermarket electronic devices are correctly installed so they will not interfere with VES system components. Assume the power steering system mechanical components are okay. Check for CCM DTCs 26, 27, 28, 44 and 45. Refer to «ENTERING DIAGNOSTICS»(/cadillac/fleetwood/ii-1993-1996/remont/electronic-steering/#steering-system-variable-effort__entering-diagnostics) . If any of these DTCs are set, repair faults before proceeding.

System Check

1. Connect Tech 1 scan tester with Mass Storage Cartridge No. 3000003 to Data Link Connector (DLC). Start engine. Select CHASSIS mode. Read VES Data on Tech 1 scan tester. Scan tester should display VES Data.
2. With engine idling, quickly turn steering wheel left and right one half turn, 2 or 3 times. Full power steering assist should be available (no lag or decrease in assist). VES current feedback should be about 90-130 milliamps. Steering wheel rotation sense voltage (input voltage) should change back and forth from 0.7 volts to 4.4 volts.
3. Command VES Test using Tech 1 scan tester. Slowly turn steering wheel left and right one half turn, 2 or 3 times. Current should increase from about 500 to 650 milliamps. A noticeable decrease in assist should be felt, especially at beginning of turns. NOTE: If system response described in previous steps is abnormal, perform remaining steps for further verification.
4. Turn engine off. Connect Power Steering Pressure Tester (J-5176-D). Warm engine to operating temperature. Idle engine. Power steering pressure should be about 150 psi.
5. Command VES Test using Tech 1 scan tester. Current should increase from about 500 to 650 milliamps. Power steering pressure should decrease to about 50 psi.

ENTERING DIAGNOSTICS

1. Turn ignition on. At Automatic Control Air Conditioning (ACAC) panel, simultaneously press OFF and WARMER (TEMP up arrow) buttons. All segments of ACAC panel should illuminate for 5 seconds. If all segments do not illuminate for 5 seconds, check for faulty ACAC panel or instrument cluster.
2. If all segments illuminate for 5 seconds, pointer number -00 should be displayed. Pointer number represents system being tested. See «POINTER NUMBER INTERPRETATION»(/cadillac/fleetwood/ii-1993-1996/remont/electronic-steering/#steering-system-variable-effort) table. To select a different pointer number (system), press FAN UP (up arrow) button to increment the pointer number, or FAN DOWN (down arrow) button to decrement the pointer number. Diagnostic Trouble Codes (DTCs) are now ready to be displayed. Go to «RETRIEVING DTCs»(/cadillac/fleetwood/ii-1993-1996/remont/electronic-steering/#steering-system-variable-effort) .

Note. Repair faults causing SIR system DTCs before repairing faults causing DTCs for any other system. If ACAC DTC 26 is set, fault causing this DTC must be repaired before checking for DTCs related to other systems. See ACAC DTC 26 under DIAGNOSTIC CHARTS. If- - (double dash) is displayed, a serial data fault exists.

POINTER NUMBER INTERPRETATION

With Tech 1 Scan Tester

Connect Tech 1 scan tester to Data Link Connector (DLC). Use Tech 1 scan tester instructions to retrieve DTCs. See VES SYSTEM DTCs table. See HISTORY & CURRENT DTCs heading below. If Tech 1 scan tester cannot communicate with serial data line, check for fault in serial data line.

Without Tech 1 Scan Tester

Enter diagnostics and select pointer number (system). See ENTERING DIAGNOSTICS . Press TEMP OUT button. If any DTCs are set, they will be displayed in ascending order (DTC of least numeric value will be displayed first). See VES SYSTEM DTCs table. See HISTORY & CURRENT DTCs heading below. To return to pointer number, press TEMP OUT button again.

History & Current DTCs

A history (intermittent) DTC indicates that the CCM previously detected the fault but the fault disappeared. A current (hard) DTC indicates that the CCM is still detecting the fault. History and current DTCs are identified as follows

1. With Tech 1 Scan Tester - The letter "H" identifies a history DTC (example: 20H, 32H, 37H). The letter "C" identifies a current DTC (example: 20C, 32C, 37C).
2. Without Tech 1 Scan Tester - If first digit of DTC is 1, DTC is a history DTC (example: 120, 132, 137). If the first digit is not a 1, the DTC is a current DTC (example: 20, 32, 37).

VES SYSTEM DTCs

Connect Tech 1 scan tester to Data Link Connector (DLC). Use Tech 1 scan tester instructions to clear DTCs. If Tech 1 scan tester cannot communicate with serial data line, check for fault in serial data line.

Enter diagnostics. See ENTERING DIAGNOSTICS . Retrieve DTCs. See RETRIEVING DTCs . While DTCs are being displayed, press OFF button. After DTCs are cleared, 00 will be displayed.

EXITING DIAGNOSTICS

To exit diagnostics at any time, press AUTO or ECON button.

TESTING

Note. To prevent misdiagnosis, perform the DIAGNOSTIC PROCEDURE (SYSTEM CHECK) under SELF- DIAGNOSTICS before performing any other tests.

FULL ASSIST (EASY STEERING) AT ALL TIMES

Note. Battery power is supplied through CCM 32-pin connector (larger of 2 connectors). When disconnecting CCM electrical connectors with battery cables connected, disconnect 32-pin connector first. When reconnecting CCM electrical connectors, reconnect 32-pin connector last. This will prevent DTCs from setting.

1. If speedometer or cruise control are inoperative, or if Powertrain Control Module (PCM) DTC 24 is set, repair fault in Vehicle Speed Sensor (VSS) circuit or replace related components as necessary. See «TESTS W/CODES»(/cadillac/fleetwood/ii-1993-1996/remont/testing-diagnostics/#engine-controls-tests-wcodes) article in ENGINE PERFORMANCE. If speedometer and cruise control are okay and PCM DTC 24 is not set, check to see if CCM DTCs 26, 27, 28, 44 or 45 are set. See «SELF-DIAGNOSTICS»(/cadillac/fleetwood/ii-1993-1996/remont/electronic-steering/#steering-system-variable-effort) .
2. If any of these DTCs are set, repair faults before proceeding. If none of these DTCs are set, perform SYSTEM CHECK again. If results in SYSTEM CHECK are normal, check for cause of intermittent condition.
3. If results in SYSTEM CHECK are abnormal, turn ignition switch to RUN position. Connect Tech 1 scan tester with Mass Storage Cartridge No. 3000003 to Data Link Connector (DLC). Start engine. Select CHASSIS mode. Select and enable VES test.
4. If VES current feedback is 500-650 milliamps, go to next step. If VES current feedback is not 500-650 milliamps, check for CCM DTC 28. Recheck wiring harness connectors at VES actuator and CCM. If connectors are okay, replace CCM.
5. Turn ignition off. Disconnect VES actuator electrical connector. Remove VES actuator. See «VES ACTUATOR»(/cadillac/fleetwood/ii-1993-1996/remont/electronic-steering/#steering-system-variable-effort) under REMOVAL & INSTALLATION. Reconnect VES actuator electrical connector and observe pintle. Turn ignition switch to RUN position.
6. Select Tech 1 scan tester CHASSIS mode. Select and enable VES test. With an assistant, observe VES actuator pintle (use a light to look into hole at pintle). Enable VES test for 3-4 seconds inward, then for 3-4 seconds outward. Do this 3 or 4 times.
7. If pintle does not move inward and outward, replace VES actuator. If pintle moves inward and outward, system is operating normally at this time. Check for intermittent fault.

DECREASED ASSIST (HARD STEERING) AT ALL TIMES

1. Disconnect VES actuator electrical connector. If symptom is no longer present, go to next step. If symptom is still present, problem is mechanical. Check power steering system. See the «STEERING SYSTEM - POWER»(/cadillac/fleetwood/ii-1993-1996/remont/manual-power-steering/#steering-system-power) article in the STEERING section.
2. Check operation of speedometer and cruise control. If speedometer and cruise control operate, go to next step. If speedometer and cruise control do not operate, repair Vehicle Speed Sensor (VSS) circuit or replace related components as necessary. See «TESTS W/CODES»(/cadillac/fleetwood/ii-1993-1996/remont/testing-diagnostics/#engine-controls-tests-wcodes) article in ENGINE PERFORMANCE.
3. Check to see if any CCM DTCs are set. See «SELF-DIAGNOSTICS»(/cadillac/fleetwood/ii-1993-1996/remont/electronic-steering/#steering-system-variable-effort) . If any CCM DTCs are set, repair faults. If no CCM DTCs are set, check for intermittent fault.

Preliminary Information

DTC 46 indicates that the CCM has detected an internal short to ground. DTC 46 sets if ignition is on and CCM detects the short for more than 2 seconds. The CCM may not operate when DTC 46 is set. If DTC 46 is a history DTC, problem may be intermittent. Ensure no wire is connected to CCM 24-pin connector terminal B5 (smaller of 2 connectors).

Test Procedure

Clear DTCs. See CLEARING DTCs under SELF-DIAGNOSTICS. Turn ignition off for at least 10 seconds. Turn ignition on. Enter diagnostics. See ENTERING DIAGNOSTICS under SELF-DIAGNOSTICS. Recheck for DTC 46. If DTC 46 is reset, replace CCM. If DTC 46 is not reset, problem is intermittent.

Note. After repairs, clear DTCs and verify system operation.

Removal

1. Siphon power steering fluid out of pump reservoir. Drain cooling system. On vehicles with belt-driven cooling fan (heavy duty cooling system), remove cooling fan pulley bracket. On all vehicles, disconnect heater hoses from water pump and position them out of way.
2. Remove pump drive belt. Disconnect fluid lines from pump. Disconnect VES actuator connector. Remove pump bolts and pump. Remove VES actuator and "O" rings from pump. (Scheme 1)

Installation

To install, reverse removal procedure using NEW lubricated "O" rings. Tighten the VES actuator to specification. Refer to the TORQUE SPECIFICATIONS table. Fill and bleed hydraulic system. Refer to HYDRAULIC SYSTEM BLEEDING under LUBRICATION.

CENTRAL CONTROL MODULE (CCM)

Note. PASS-Key II(R) system (anti-theft system) uses an ignition key that is electrically coded to match the CCM. If CCM is being replaced, ensure coding of new CCM matches coding of ignition key.

Removal & Installation

Turn ignition off. Disconnect negative battery cable. Remove nuts securing CCM to plastic tray. Remove CCM. Disconnect CCM electrical connectors. To install, reverse removal procedure. If installing new CCM, transfer fastener studs from old CCM to new CCM.

TORQUE SPECIFICATIONS

TORQUE SPECIFICATIONS

ACAC DTC 26 - SERIAL DATA COMMUNICATION (CIRCUIT SHORTED TO GROUND, SHORTED TO BATTERY OR OPEN)

Note. In wiring diagram and diagnostic chart, H-A/C control refers to ACAC control panel.

Serial data link connects ACAC control panel to PCM, which is the master controller of the serial data link system. DTC 26 sets if ignition is on, and one or more of the following conditions occurs in Tan wire

1. Short To Ground
2. Short To Battery
3. Open Between ACAC Control Panel And Splice S223.

If DTC 26 is a current DTC, communication may be lost on the serial data link. DTC 26 clears when circuit is repaired.

Diagnostic Aids

Check for intermittent open in Tan wire. If DTC 26 is a current DTC, the ACAC control panel will turn on the A/C compressor clutch.

Note. Test numbers refer to numbers on diagnostic chart.

1. Checks for DTCs and should clear any intermittent DTCs.
2. Checks for normal serial data voltage at terminal "M" of DLC.
3. Checks for open Tan wire.

Note. After repairs, clear DTCs and verify system operation.

Scheme 2

Scheme 3

CCM DTC 26 - VES OUTPUT CIRCUIT OPEN OR SHORTED TO GROUND

Note. In wiring diagram and diagnostic chart, P/S PUMP AND EVO ACTUATOR refers to VES actuator.

CCM applies a Pulse Width-Modulated (PWM) current to the VES actuator through Brown and White wires. Every ignition cycle, CCM checks for an open or short to ground in this circuit under the following conditions

1. Ignition On
2. VES Function Off
3. Brown Wire Not Grounded By CCM
4. Voltage At CCM Connector Terminal C13 Is Less Than 2 Volts (102A/D Counts).

If CCM detects an open or short to ground in this circuit, it sets DTC 26 and disables VES system. DTC 26 will clear if CCM does not detect fault for 2 seconds.

If DTC 26 is a history DTC, problem may be intermittent. See RETRIEVING DTCs under SELF-DIAGNOSTICS. Perform test while wiggling wiring harness. Check for poor electrical connections at CCM and VES actuator.

Note. Test numbers refer to numbers on diagnostic chart.

1. Checks VES circuit resistance.
2. Checks for short to ground in VES circuit.
3. Isolates VES actuator from circuit, and checks for short to ground.
4. Isolates VES actuator from circuit, and checks for open.
5. Isolates VES actuator from circuit, and checks for short to ground.

Note. After repairs, clear DTCs and verify system operation.

Scheme 4

Scheme 5

CCM DTC 27 - VES OUTPUT CIRCUIT SHORTED TO BATTERY

Note. In wiring diagram and diagnostic chart, P/S PUMP AND EVO ACTUATOR refers to VES actuator.

CCM applies a Pulse Width-Modulated (PWM) current to the VES actuator through Brown and White wires. Every ignition cycle, CCM checks for a fault in this circuit under the following conditions

1. Ignition On
2. VES Function Off
3. Brown Wire Not Grounded By CCM

During test, if CCM detects voltage at CCM connector terminal C13 exceeds 3 volts, it sets DTC 27 and disables VES system. If CCM does not detect fault for 2 seconds, DTC 27 clears.

If DTC 27 is a history DTC, problem may be intermittent. See RETRIEVING DTCs under SELF-DIAGNOSTICS. Perform test while wiggling wiring harness. Check for intermittent short to battery in VES actuator circuit.

Note. Test numbers refer to numbers on diagnostic chart. Checks for shorted solenoid windings in VES actuator. Checks for short to battery in Brown wire. Checks for short to battery in White wire.

Note. After repairs, clear DTCs and verify system operation.

Scheme 6

CCM DTC 28 - VES TRACKING ERROR DETECTED (CIRCUIT OPEN, SHORTED TO GROUND OR SHORTED TO BATTERY)

Note. If DTCs 26 or 27 are set, repair faults causing these DTCs before continuing this procedure. In wiring diagram and diagnostic chart, P/S PUMP AND EVO ACTUATOR refers to VES actuator.

CCM applies a Pulse Width-Modulated (PWM) current to the VES actuator through Brown and White wires. Every ignition cycle, CCM checks for a fault in this circuit under the following conditions

1. VES Function Is On At Low Vehicle Speeds And VES Feedback Exceeds 260 Milliamps
2. VES Function Is On At High Vehicle Speeds And VES Feedback Is Less Than 360 Milliamps

During test, if CCM detects circuit is shorted to battery, shorted to ground, or open, it sets DTC 28 and disables VES system. When ignition is turned off and then on again, DTC 28 clears.

If DTC 28 is a history DTC, problem may be intermittent. See RETRIEVING DTCs under SELF-DIAGNOSTICS. Check for intermittent fault by wiggling wiring harness during test.

Note. Test numbers refer to numbers on diagnostic chart.

1. Checks for short or high resistance in VES circuit.
2. Checks for high resistance in VES circuit.

Note. After repairs, clear DTCs and verify system operation.

Scheme 7

CCM DTC 44 - STEERING WHEEL SENSOR CIRCUIT OPEN OR SHORTED TO GROUND

Steering wheel speed sensor is a potentiometer. If CCM detects a short to ground or an open in Red or Light Green wires, it sets DTC 44 and disables VES system. DTC 44 sets if ignition is on and sense voltage (input voltage) is greater than .254 volts for more than 0.2 second. If CCM does not detect fault for 2 seconds, DTC 44 clears.

Check for loose connections or damaged connectors at CCM and steering wheel speed sensor. If condition is intermittent, wiggle wiring harness while VES system is operating. Input voltage to the steering wheel speed sensor can be monitored with a Tech 1 scan tester.

Note. Test numbers refer to numbers on diagnostic chart.

1. Checks for open or short to ground in steering wheel speed sensor.
2. Checks for in Red or Light Green wire.
3. Checks for open in Red wire.
4. Checks for open in Light Green wire.

Note. After repairs, clear DTCs and verify system operation.

Scheme 8

Scheme 9

CCM DTC 45 - STEERING WHEEL SENSOR CIRCUIT OPEN OR SHORTED TO BATTERY

Steering wheel speed sensor is a potentiometer. If CCM detects a short to ground, an open or a short to battery in Red or Light Green wires, it sets DTC 44 and disables VES system. DTC 44 sets if ignition is on and sense voltage (input voltage) is 4.740 volts or greater for more than 0.2 second. If CCM does not detect fault for 2 seconds, DTC 44 clears.

Input voltage to the steering wheel speed sensor can be monitored with a Tech 1 scan tester while turning steering wheel or road testing vehicle. An open Black wire will cause DTC 44 to set because sense voltage will always be high.

Note. Test numbers refer to numbers on diagnostic chart.

1. Checks for defective steering wheel speed sensor.
2. Checks for short to battery in Red and Light Green wires.
3. Checks continuity of Black wire.

Note. After repairs, clear DTCs and verify system operation.

Scheme 10

Variable Effort Steering (VES) System Wiring Diagram. Scheme 11

See also:
• TROUBLE SHOOTING - BASIC PROCEDURES
• STEERING SYSTEM - POWER
• TESTS W/CODES
• SELF-DIAGNOSTICS
• FULL ASSIST (EASY STEERING) AT ALL TIMES
• DECREASED ASSIST (HARD STEERING) AT ALL TIMES
• ENTERING DIAGNOSTICS
• HISTORY & CURRENT DTCs
• DIAGNOSTIC PROCEDURE (SYSTEM CHECK)
• HYDRAULIC SYSTEM BLEEDING