GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2004 🢒 Seville 🢒 Brakes 🢒 Antilock Brake System 🢒 Vehicle Stability Enhancement System Excessive Brake Pulsation

Circuit Description

The vehicle stability enhancement system (VSES) is activated by the electronic brake control mdoule (EBCM) calculating the desired yaw rate and comparing it to the actual yaw rate input. The desired yaw rate is calculated from measured steering wheel position, vehicle speed, and lateral acceleration. The difference between the desired yaw rate and actual yaw rate is the yaw rate error, which is a measurement of oversteer or understeer. If the yaw rate error becomes too large, the EBCM will attempt to correct the vehicle's yaw motion by applying differential braking to the left or right front wheel.

The amount of differential braking applied to the left or right front wheel is based on both the yaw rate error and side slip rate error. The side slip rate error is a function of the lateral acceleration minus the product of the yaw rate and vehicle speed. The yaw rate error and side slip rate error are combined to produce the total delta velocity error. When the delta velocity error becomes too large and the VSES system activates, the drivers steering inputs combined with the differential braking will attempt to bring the delta velocity error toward zero.

The VSES activations generally occur during aggressive driving, in the turns or bumpy roads without much use of the accelerator pedal. When braking during VSES activation, the brake pedal will feel different than the ABS pedal pulsation. The brake pedal pulsates at a higher frequency during VSES activation.

Step

Action

Values

Yes

No

Schematic Reference: Antilock Brake System Schematics

1

Did you perform the ABS Diagnostic System Check?

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Go to Step 2

Go to Diagnostic System Check - ABS

2
  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. Select the display DTCs function on the scan tool for the powertrain control module (PCM).

Does the scan tool display DTC P1575?

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Go to DTC P1575 in Cruise Control

Go to Step 3

3
  1. With a scan tool, observe the Extended Travel Brake Switch parameter in the DRP/ABS/TCS data list.
  2. Step on and off the brake pedal with enough force to simulate a hard braking condition. As the brake pedal is pressed and released, the scan tool should read Applied and Released.
  3. Use a tape measure in order to measure the distance that the brake pedal travels for the scan tool to read Applied.

Does the distance measure within the specified range?

2.5-3.3 cm (1.0-1.3 in)

Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems

Go to Step 4

4

Adjust or repair the extended travel brake switch as necessary. Refer to Stop Lamp Switch Replacement or Stop Lamp Switch Adjustment in Lighting Systems.

Did you complete the repair?

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Go to Step 5

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5

Operate the system in order to verify the repair.

Did you correct the condition?

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System OK

Go to Step 2