Variable Effort Steering System Buick Park Avenue II рестайлинг

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Diagnostic Starting Point-Variable Effort Steering

Begin the system diagnosis with the DIAGNOSTIC SYSTEM CHECK-VARIABLE EFFORT STEERING . The Diagnostic System Check will provide the following information

1. The identification of the control modules which command the system
2. The ability of the control modules to communicate through the serial data circuit
3. The identification of any stored diagnostic trouble codes (DTCs) and their status

The use of the Diagnostic System Check will identify the correct procedure for diagnosing the system and where the procedure is located.

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Scan Tool Data Definitions

ABS Reference Speed: The scan tool displays 0-255 km/h (0-159 mph). The vehicle speed from the average of all four wheel speeds.

Ignition Voltage: The scan tool displays 0-17 Volts. The level of the ignition voltage at the EBCM.

LF Wheel Speed: The scan tool displays 0-255 km/h (0-159 mph). The actual speed of the left front wheel.

LR Wheel Speed: The scan tool displays 0-255 km/h (0-159 mph). The actual speed of the left rear wheel.

MagnaSteer(R) Commanded Current: The scan tool displays 0.00 to 3.00 amps. The amount of current that the EBCM is commanding to the variable effort steering (VES) actuator.

MagnaSteer(R) Failed: The scan tool displays Yes or No. Yes indicates the VES system is disabled due to a malfunction. No indicates the system is operating to specifications.

MagnaSteer(R) Feedback Current: The scan tool displays 0.00 to 3.00 amps. The amount of current returning to the EBCM from the VES actuator.

MagnaSteer(R) Indicator/Message: the scan tool displays Off or On. The status of the VES indicator or message, if equipped. Indicates if the VES indicator or message is currently on or off.

RF Wheel Speed: The scan tool displays 0-255 km/h (0-159 mph). The actual speed of the right front wheel.

RR Wheel Speed: The scan tool displays 0-255 km/h (0-159 mph). The actual speed of the right rear wheel.

Switched System Battery Voltage: The scan tool displays 0-17 Volts. The voltage available to the EBCM when the ABS relay is energized.

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DIAGNOSTIC TROUBLE CODE (DTC) IDENTIFICATION

Circuit Description

The Variable Effort Steering (VES) system uses the Electronic Brake Control Module (EBCM) to command current from zero amps to positive three amps to an electromagnetic rotary actuator. The VES system uses the Anti-Lock Brake System (ABS) wheel speed sensor inputs to determine vehicle speed. At low speeds, no current is commanded and steering is assisted by hydraulics only. At high speeds, A positive current is commanded to the VES actuator to create steering resistance. The EBCM monitors and compares commanded and feedback currents to detect malfunctions in the VES actuator or the circuits to the actuator.

Conditions for Running the DTC

1. Ignition voltage between 10.5-17 volts
2. Off state test-initial ignition ON, no engine RPM, or vehicle speed present.
3. On state test-if off state test passes, engine RPM and vehicle speed present.

Condition for Setting the DTC

An open, short to ground, or short to voltage in the VES actuator, or the circuits to the actuator.

Action Taken When the DTC Sets

1. A DTC C1241 is stored in memory.
2. The DIG may display the SERVICE STEERING SYS warning message.
3. The VES system is disabled.

Conditions for Clearing the DTC

1. A current DTC will clear when the malfunction is no longer present.
2. A history DTC will clear after 100 consecutive ignition cycles with no malfunction present.
3. Using the scan tool

Diagnostic Aids

The vehicle needs to be driven to view the full commanded and feedback current ranges.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

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1. 2. Tests if the commanded and feedback current parameters are in specified range in there active state.
2. 3. Tests if the VES actuator resistance is within specified range.
3. 11. Perform the setup procedure after EBCM replacement.

The Variable Effort Steering (VES) System or MAGNASTEER-(MAG-e)(R) varies the amount of effort needed to steer the vehicle as wheel speed changes. At low speeds, the steering is assisted by hydraulics only, which provides maximum steering assist for easy turning and parking maneuvers. At high speeds, steering effort is increased to provide firmer steering (road feel) and directional stability. The Electronic Brake Control Module (EBCM) controls an electromagnetic rotary actuator located in the steering rack and pinion. The EBCM varies the steering assist by adjusting the current flow through the actuator. The actuator adjusts the amount of steering assist to achieve a given level of effort to steer the vehicle. The VES system accomplishes this by subtracting torque on the input shaft to the rack and pinion. The main component of the system is an electromagnetic actuator, which consists of a pole piece, and an electromagnetic coil assembly. The VES system uses the anti-lock brake (ABS) wheel speed sensor inputs to the EBCM to determine the desired amount of steering assist. When the EBCM senses wheel speed, it commands a current that is most appropriate for each speed. This current then energizes the actuator. The EBCM commands current from zero amps to positive three amps. At low speeds, no current is commanded, and steering is assisted by hydraulics only. At high speeds, a positive current is commanded which creates steering resistance. Ignition voltage and ground are provided through the EBCM. The EBCM has the ability to detect malfunctions in the actuator or the circuitry to the actuator. Any malfunctions detected will cause the system to ramp to zero amps and steering will be assisted by hydraulics only.

See also:
• DIAGNOSTIC SYSTEM CHECK-VARIABLE EFFORT STEERING