Cruise Control System Buick Century VI

Specifications

Fastener Tightening Specifications

Schematic and Routing Diagrams

1. For Century cruise control schematic refer to «CRUISE CONTROL»(ref-154365-S15719065472003080900000) in wiring systems.
2. For Regal cruise control schematic refer to «CRUISE CONTROL»(ref-154369-S38899868352003080900000) in wiring systems.

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Diagnostic Starting Point - Cruise Control

Begin the system diagnosis with DIAGNOSTIC SYSTEM CHECK - CRUISE CONTROL . The Diagnostic System Check will provide the following information

1. The identification of the control module(s) which command the system
2. The ability of the control module(s) 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.

Test Description

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

1. 2. Lack of communication may be due to a partial malfunction of the class 2 serial data circuit or due to a total malfunction of the class 2 serial data circuit. The specified procedure will determine the particular condition.
2. 3. The symptom list in Symptoms will determine the correct diagnostic procedure to use.

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Scan Tool Data Definitions

Cruise Active: Displays Disengaged or Engaged. The status of the cruise engaged signal. The cruise control module grounds the circuit when cruise control is on.

Cruise Inhibit Reason: The scan tool displays the last 6 cruise control disengages in order from 1 to 6. There are 20 possible causes for the cruise control to disengage.

Cruise Inhibit Signal Command: Displays ON or OFF. Indicates if the PCM is commanding the cruise control module to inhibit cruise control operation.

Diagnostic Trouble Code (DTC) List

Diagnostic Trouble Code (DTC) List

Circuit Description

The PCM inhibits cruise control operation when certain conditions are detected.

The PCM removes the ground from the cruise control inhibit signal circuit in order to disengage cruise control operation. The cruise control module monitors the cruise control inhibit signal circuit in order to determine when to inhibit cruise.

When the cruise control module (CCM) activates cruise control operation, the CCM provides a ground for the cruise control engaged signal circuit. The PCM monitors the cruise control engaged signal circuit in order to determine that cruise control is engaged.

Conditions for Running the DTC

The PCM inhibits cruise control operation by removing the ground from the cruise control inhibit signal circuit.

Conditions for Setting the DTC

1. The PCM detects a cruise control engaged signal from the cruise control module, while inhibiting cruise control operation.
2. The above condition is present for more than 1 second.

Action Taken When the DTC Sets

1. The PCM does not illuminate the malfunction indicator lamp (MIL).
2. The PCM stores conditions which were present when the DTC set as Failure Records only. This information will not be stored as Freeze Frame Records.

Conditions for Clearing the MIL/DTC

1. The DTC becomes history when the conditions for setting the DTC are no longer present.
2. The history DTC clears after 40 warm-up cycles.
3. The PCM receives a clear code command from the scan tool.

Scheme 9

The PCM removes the ground from the cruise control inhibit signal circuit when it determines that conditions exist for which cruise control should not be enabled. The PCM also monitors the voltage on this circuit in order to determine if a fault exists.

1. The engine speed is greater than 450 RPM.
2. The ignition is ON.
3. The system voltage is between 8 volts and 16 volts.

1. The PCM detects that an improper voltage exists on the cruise control inhibit signal circuit.
2. The condition exists for at least 30 seconds.

1. The PCM does not illuminate the malfunction indicator lamp (MIL).
2. The PCM stores the conditions present when the DTC set as Failure Records data only.

Conditions for Clearing the DTC

1. The history DTC clears after 40 malfunction free warm-up cycles.
2. The PCM receives a clear code command from the scan tool.

Diagnostic Aids

In order to determine whether an improper voltage level exists on the output circuit, the PCM compares the voltage level to the commanded state.

If the condition is intermittent, refer to TESTING FOR INTERMITTENT AND POOR CONNECTIONS in Wiring Systems.

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Symptoms - Cruise Control

Visual/Physical Inspection

1. Inspect for aftermarket devices which could affect the operation of the Cruise Control System. Refer to CHECKING AFTERMARKET ACCESSORIES in Wiring Systems.
2. Inspect the easily accessible or visible system components for obvious damage or conditions which could cause the symptom.

Intermittent

Faulty electrical connections or wiring may be the cause of intermittent conditions. Refer to TESTING FOR INTERMITTENT AND POOR CONNECTIONS in Wiring Systems.

Symptom List

Refer to a symptom diagnose procedure from the following list in order to diagnose the symptom

1. «CRUISE CONTROL INOPERATIVE/MALFUNCTIONING»(/buick/century/vi-1997-2005/remont/cruise-control-systems/#cruise-control-system)
2. «CRUISE CONTROL INDICATOR INOPERATIVE»(/buick/century/vi-1997-2005/remont/cruise-control-systems/#cruise-control-system)

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To avoid misdiagnosis

1. Inspect for proper operation of the brake lamps.
2. Inspect throttle linkage for mechanical binding which could cause the system to malfunction.
3. Inspect cruise control cable for adjustment. It should have minimum slack.
4. EMI on the speed sensor signal circuit may cause erratic cruise control operation.

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Removal Procedure

1. Disconnect the cable adjuster lock.
2. Rotate the cruise control cable counterclockwise. Remove the cruise control cable from the cruise control module.
3. Remove the cruise control cable from the cruise control module strap.
4. Remove the cruise control cable from the cruise control cable retainers.
5. Remove the cruise control cable from the throttle lever and the accelerator control cable bracket.
6. Remove the cruise control cable from the engine.

Scheme 15

1. Install the cruise control cable to the engine.
2. Install the cruise control cable to the throttle lever and the accelerator control cable bracket.
3. Install the cruise control cable to the cruise control retainers.
4. Install the cruise control cable to the cruise control module strap. IMPORTANT: Ensure the cruise control module strap is not twisted during installation of the cruise control cable.
5. Rotate the cruise control cable clockwise. Install the cruise control cable to the cruise control module.

1. Disconnect the cable adjuster lock.
2. Rotate the cruise control cable counterclockwise. Remove the cruise control cable from the cruise control module.
3. Remove the cruise control cable from the cruise control module strap.
4. Remove the cruise control cable from the cruise control cable retainers.
5. Remove the cruise control cable from the throttle lever and the accelerator control cable bracket.
6. Remove the cruise control cable from the engine.

Scheme 16

1. Install the cruise control cable to the engine.
2. Install the cruise control cable to the throttle lever and the accelerator control cable bracket.
3. Install the cruise control cable to the cruise control retainers.
4. Install the cruise control cable to the cruise control module strap. IMPORTANT: Ensure the cruise control module strap is not twisted during installation of the cruise control cable.
5. Rotate the cruise control cable clockwise. Install the cruise control cable to the cruise control module.

1. Remove the cruise control cable from the cruise control module. Refer to «CRUISE CONTROL CABLE REPLACEMENT (3.1L)»(/buick/century/vi-1997-2005/remont/cruise-control-systems/#cruise-control-system) or «CRUISE CONTROL CABLE REPLACEMENT (3.8L)»(/buick/century/vi-1997-2005/remont/cruise-control-systems/#cruise-control-system) .
2. Disconnect the electrical connector from the cruise control module.
3. Remove the cruise control module retaining nuts from the shock tower.

Installation Procedure

1. Install the cruise control module on the shock tower mounting studs. NOTE: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.
2. Install the cruise control module retaining nuts. Tighten Tighten the cruise control module to shock tower nuts to 2 N.m (18 lb in).
3. Connect the electrical connector to the cruise control module.
4. Install the cruise control cable to the cruise control module. Refer to «CRUISE CONTROL CABLE REPLACEMENT (3.1L)»(/buick/century/vi-1997-2005/remont/cruise-control-systems/#cruise-control-system) or «CRUISE CONTROL CABLE REPLACEMENT (3.8L)»(/buick/century/vi-1997-2005/remont/cruise-control-systems/#cruise-control-system) .

Cruise Release Switch Adjustment

1. Remove the left instrument panel insulator. Refer to CLOSEOUT/INSULATOR PANEL REPLACEMENT - LEFT in Instrument Panel, Gages and Console.
2. Press the brake pedal fully.
3. Push the switches into the retainers until the switches are fully seated.
4. Pull the brake pedal fully rearward against the pedal stop until the audible clicks can no longer be heard.
5. Measure the brake pedal travel distances from the centerline of the brake pedal pad. Compare the measurements to the following values. The comparison of the values can verify that the cruise control release switch and the stop lamp switch are correctly adjusted: The cruise control release switch and the stop lamp switch contacts must actuate at 3.5-12.5 mm (0.125-0.500 in) of brake pedal travel. Nominal actuation of the stop lamp switch contacts occurs about 4.5 mm (0.2 in) beyond the point of cruise control release switch actuation.
6. Install the left instrument panel insulator. Refer to CLOSEOUT/INSULATOR PANEL REPLACEMENT - LEFT in Instrument Panel, Gages and Console.

1. Remove the left instrument panel insulator. Refer to CLOSEOUT/INSULATOR PANEL REPLACEMENT - LEFT in Instrument Panel, Gages and Console.
2. Disconnect the cruise release switch electrical connector.
3. Remove the cruise release switch from the cruise release switch retainer on the brake pedal bracket.

1. Install the cruise release switch to the cruise release switch retainer on the brake pedal bracket.
2. Connect the cruise release switch electrical connector.
3. Adjust the cruise release switch. Refer to «CRUISE RELEASE SWITCH ADJUSTMENT»(/buick/century/vi-1997-2005/remont/cruise-control-systems/#cruise-control-system__cruise-release-switch-adjustment) .
4. Install the left side instrument panel insulator. Refer to CLOSEOUT/INSULATOR PANEL REPLACEMENT - LEFT in Instrument Panel, Gages and Console.

Cruise Control Description and Operation

Cruise control is a speed control system that maintains a desired vehicle speed under normal driving conditions. However, steep grades may cause variations in the selected speeds. The electronic cruise control system has the capability to CRUISE, COAST, RESUME SPEED, ACCELERATE, and TAP-UP or TAP-DOWN.

The main parts of the cruise control system are

1. The cruise control module assembly
2. The function control switches
3. The cruise control release switch
4. The stoplamp switch assembly
5. The vehicle speed sensor

The cruise control system uses the cruise control module assembly to maintain the desired vehicle cruise speed and operation. The cruise control module assembly has a controller and an electric stepper motor to vary the throttle in each different cruise control mode. The controller monitors vehicle speed and operates the stepper motor. The stepper motor operates in response to the controller, to maintain the desired cruise speed. The electric stepper motor moves a strap that is attached to the cruise control cable which moves the throttle linkage. The cruise control module assembly contains a low speed limit which will prevent system engagement below a minimum speed of 40 km/h (25 mph). The module assembly is not serviceable.

The operation of the controller is controlled by the function control switches located on the multifunction turn signal lever or optional steering wheel controls. The cruise control functional control switches include the ON/OFF, SET/COAST, R/A (resume/accelerate). The switches provide driver control of the cruise control system.

The cruise control release switch and stoplamp switch are used to disengage the cruise control. A release switch assembly and a stoplamp switch assembly are mounted on the brake pedal bracket. To disengage the system the driver presses the brake pedal. The speed of the vehicle at brake actuation will be stored in the memory of the cruise module.

With cruise control, you can maintain a speed of about 40 km/h (25 mph) or more without keeping your foot on the accelerator. When the driver turns off the on/off switch or ignition switch, the cruise control turns off. The vehicle speed stored in the memory of the cruise module will be lost.

Ignition positive voltage is supplied from the cruise fuse, to the cruise control module. The cruise control module is grounded to the chassis. When the cruise control ON/OFF switch is on, ignition positive voltage is applied to the cruise control on switch signal circuit of the cruise control module. If the driver has not pressed the brake pedal, ignition positive voltage is supplied through the cruise release switch, to the cruise release signal circuit of the cruise control module. When the driver presses the brake pedal, battery positive voltage is supplied from the stop lamp fuse, through the closed stop lamp switch to the stop lamp switch signal circuit of the cruise control module. When the SET/COAST button is pressed, ignition positive voltage is applied to the cruise control set/coast switch signal circuit of the cruise control module. When pressing the R/A (resume/accelerate), ignition positive voltage is applied to the cruise control resume/accelerate switch signal circuit of the cruise control module.

The cruise control module receives a vehicle speed signal input from the Powertrain Control Module (PCM). In operation, the voltage varies between 0 V and 5 V.

The cruise control module, cruise engaged circuit, sends a signal to the PCM when cruise is engaged. The cruise control module, cruise inhibit signal circuit, is a circuit used by the PCM to disengage cruise control when conditions inconsistent with cruise operation are present.

After the cruise control engaged criteria has been met and the cruise ON and Set/Coast have been commanded, the cruise control module sends a signal to the PCM that the cruise control is engaged. The PCM then sends a class 2 message to the instrument panel cluster (IPC) to illuminate the cruise light, if equipped.

The PCM will inhibit cruise control

1. When vehicle speed is less than 40 km/h (25 mph).
2. When PARK, REVERSE, NEUTRAL, or 1st gear is indicated.
3. With low engine RPM
4. With high engine RPM (fuel cut-off)
5. When vehicle speed is to high
6. When an over or under charged battery voltage condition exists
7. Anti-lock brake system/traction control system is active for more than 2 seconds

If the PCM determines that any of the cruise control inhibit conditions are present, the PCM will disengage the cruise control. The PCM accomplishes this by opening the cruise control inhibit signal circuit.

See also:
• DIAGNOSTIC TROUBLE CODE (DTC) LIST
• DTC P0502: VEHICLE SPEED SENSOR CIRCUIT (LOW INPUT)
• DTC P0503: VEHICLE SPEED SENSOR CIRCUIT PERFORMANCE
• DIAGNOSTIC TROUBLE CODE DEFINITIONS
• DIAGNOSTIC SYSTEM CHECK - CRUISE CONTROL
• CRUISE CONTROL DESCRIPTION AND OPERATION
• CRUISE RELEASE SWITCH ADJUSTMENT