Cruise Control System Buick LeSabre VIII

FASTENER TIGHTENING SPECIFICATIONS

Fastener Tightening Specifications

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DIAGNOSTIC STARTING POINT - CRUISE CONTROL

Begin the system diagnosis with the 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 presence of DTCs which begin with "U" indicate some other module is not communicating. The specified procedure will compile all the available information before tests are performed.
3. 4 The presence of DTCs which pertain to the ABS/TCS system must be diagnosed first. The specified procedure will compile all the available information before tests are performed.
4. 5 The presence of DTCs which pertain to the transaxle must be diagnosed after any ABS/TCS codes. The specified procedure will compile all the available information before tests are performed.

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SCAN TOOL DATA DEFINITIONS (CRUISE CONTROL)

1. Brake Switch Displays Released or Applied. The current status of the brake switch.
2. Cruise Displays Disengaged or Engaged. The status of the cruise engaged signal. The cruise control module grounds the circuit when cruise control is on.
3. Cruise Inhibit Reason Displays the reason the PCM inhibits the cruise operation.
4. Cruise Inhibit Signal Command Displays On or Off. Indicates if the PCM is commanding the cruise control module to inhibit cruise control operation.

SCAN TOOL DATA DEFINITIONS (DISENGAGE HISTORY)

1. Important The following data list terms MAY NOT apply to all vehicle lines.
2. ABS Anti-lock Brake (ABS) is active.
3. ALDL A scan tool message to inhibit cruise control operation is received by the PCM.
4. Brake A class 2 message is received by the PCM that a basic brake problem has occurred.
5. Battery Voltage The battery positive voltage is out of range.
6. Clutch Switch A failure of the clutch switch has been detected.
7. CC Cancel Switch A class 2 message is received by the PCM that a cruise cancel event has occurred.
8. CC Inhibit Circuit A fault on the cruise control inhibit signal circuit has been detected.
9. Delta Vehicle Speed When the vehicle speed is greater or less than the cruise control operating criteria speed.
10. Engine Not Running Engine is not running.
11. Engine Run Time When the engine run time does not equal the cruise control enable criteria run time.
12. Engine Speed When vehicle speed is greater or less than the cruise control enable criteria speed.
13. Injector When any number of injectors are disabled by high mph.
14. Manual/Neutral CC Vehicle is shifted into neutral while cruise control is in operation.
15. MPH Limited When mph is limited, by the PCM controlling the fuel and electronic spark timing.
16. P0751 1-2 shift solenoid valve performance.
17. P0753 1-2 shift solenoid control circuit fault.
18. P0756 2-3 shift solenoid valve performance.
19. P0758 2-3 shift solenoid control circuit fault.
20. P0785 3-2 shift solenoid control circuit fault.
21. Park Brake Active A Class 2 message is received by the PCM that the parking brake is active.
22. Serial Communications A class 2 serial communication problem is detected.
23. SMCC Fault A fault is detected with the stepper motor cruise control module.
24. TCS When the traction control is active.
25. Trans When the clutch pedal is pressed on a manual transmission vehicle or when the gear selector is shifted out of DRIVE during cruise control operation.
26. Vehicle Speed Fault When a problem is detected with vehicle speed.
27. Vehicle Speed Vehicle speed drops below the cruise control engaged criteria.
28. Active Brake Yaw A Class 2 message is received by the PCM that the Brake Yaw is active.
29. Brake The PCM senses any brake active operation.

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Circuit Description

The PCM inhibits cruise control operation when certain conditions are directed. The PCM provides a ground for the cruise control inhibit signal circuit in order to disengage the cruise control operation.

Conditions For Running DTC

The PCM is commanding the cruise control module to inhibit cruise control operation.

Conditions For Setting DTC

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

Action Taken When DTC Sets

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 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 malfunction free warm-up cycles.
3. The PCM receives a clear code command from the scan tool.

Diagnostic Aids

Check for the following conditions

1. Inspect the harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and faulty terminal to wire connections. Use a corresponding mating terminal to test for proper terminal tension.
2. If the harness appears to be OK, observe the Cruise Status display on the scan tool while moving the connectors and wiring harnesses related to the cruise control module. A change in the display will indicate the location of the malfunction.

If DTC P1554 cannot be duplicated, the information included in the Failure Records data can be useful in determining how many ignition cycles have passed since the DTC was last set.

The number below refers to the step number on the diagnostic table.

1. 8 This vehicle is equipped with a PCM which utilizes an Electrically Erasable Programmable Read-Only Memory (EEPROM). When the PCM is replaced, the new PCM must be programmed.

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This diagnostic test functions on the assumption that a brake application causes a sudden decrease in non-drive wheel speed.

The extended travel brake switch is a normally closed switch. When the extended travel brake switch is closed, the PCM senses ignition voltage on the extended travel brake switch signal circuit.

If the PCM senses voltage on the extended travel brake switch signal circuit when the extended travel brake switch should be open, DTC P1575 will set.

1. The engine speed is more than 700 RPM.
2. The engine has been operating more than 2 seconds.
3. The diagnostic will disable when the wheel speed is below 10 MPH.
4. The vehicle speed is decreasing at a rate more than 10.4 MPH over a one second period.

1. The PCM detects voltage on the extended travel brake switch circuit when the extended travel brake switch should be open.
2. The above conditions are present for 1.5 seconds.

1. The PCM stores the DTC information into memory when the diagnostic runs and fails.
2. The Malfunction Indicator Lamp (MIL) will not illuminate.
3. The PCM stores this information in the Failure Records.

Conditions For Clearing DTC

1. A last test failed (current DTC) clears when the diagnostic runs and does not fail.
2. A history DTC clears after 40 consecutive warm-up cycles, if this or any other emission related diagnostic does not report any failures.
3. Use a scan tool in order to clear the DTC or disconnect the PCM battery feed.

Note. Remove any debris from the PCM connector surfaces before servicing the PCM. Inspect the PCM connector gaskets when diagnosing or replacing the modules. Ensure that the gaskets are installed correctly. The gaskets prevent contaminate intrusion into the PCM.

In order to adjust the extended travel brake switch perform the following

1. With the brake pedal pressed, insert the appropriate brake lamp switch into the retainer until the switch body seats in the retainer. You can hear clicks as you push the threaded portion of the switch through the retainer.
2. Slowly pull the brake pedal fully rearward against the stop until you can no longer hear the clicks.

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

1. 2 This step determines if the fault is present.
2. 4 This step checks for a Extended Travel Brake Switch circuit for being shorted to B+.
3. 9 This DTC will not report a pass. The scan tool status for this DTC will never report a pass. The scan tool will only display when the diagnostic fails. The repair is not complete if the scan tool indicates that the diagnostic ran and failed.

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Output Driver Modules (ODMs) are used by the Powertrain Control Module (PCM) in order to turn on many of the current-driven devices that are needed to control various engine and transaxle functions. DTC P1558 set indicates that an improper voltage level has been detected on the output circuit which controls the cruise control inhibit circuit.

1. The engine speed is 450 RPM or more.
2. System voltage is between 8 and 16 volts.

1. The ignition is on.
2. The PCM detects an improper voltage level on the cruise inhibit signal circuit.
3. The condition exists for at least 30 seconds.

1. The PCM will not illuminate the Malfunction Indicator Lamp (MIL).
2. The PCM will store the conditions present when the DTC set as Failure Records data only.

1. The history DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction.
2. The DTC can be cleared by using the scan tool's Clear DTC Information function.

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 .

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

1. 2 Normally, ignition positive voltage should be present on the control circuit with the PCM disconnected and the ignition turned ON.
2. 3 Tests for short to voltage on the control circuit.
3. 8 This vehicle is equipped with a PCM which utilizes an Electrically Erasable Programmable Read Only Memory (EEPROM). When the PCM is being replaced, the new PCM must be programmed.

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SYMPTOMS - CRUISE CONTROL

Note. The following steps must be completed before using the symptom tables.

1. Perform the «DIAGNOSTIC SYSTEM CHECK - POWER SEAT SYSTEMS»(/buick/lesabre/viii-2000-2005/remont/seats/#power-seat-system) in Seats, before using the Symptom Tables in order to verify that all of the following are true: There are no DTCs set. The control modules can communicate via the serial data link.
2. Review the system operation in order to familiarize yourself with the system functions. Refer to «CRUISE CONTROL DESCRIPTION & OPERATION»(/buick/lesabre/viii-2000-2005/remont/cruise-control-systems/#cruise-control-system__cruise-control-description-operation) .

Visual/Physical Inspection

1. Refer to «CHECKING AFTERMARKET ACCESSORIES»(/buick/lesabre/viii-2000-2005/remont/cruise-control-systems/#cruise-control-system__checking-aftermarket-accessories) .
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 & POOR CONNECTIONS .

Symptom List

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

1. «CRUISE CONTROL INOPERATIVE/MALFUNCTIONING»(/buick/lesabre/viii-2000-2005/remont/cruise-control-systems/#cruise-control-system)

CHECKING AFTERMARKET ACCESSORIES

Do not connect aftermarket accessories into the following circuits

1. SIR circuits, all such circuits are indicated on circuit diagrams with the SIR symbol.
2. OBD II circuits, all such circuits are indicated on circuit diagrams with the OBD II symbol.

Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problems.

Possible causes of vehicle problems related to aftermarket accessories include

1. Power feeds connected to points other than the battery.
2. Antenna location.
3. Transceiver wiring located too close to vehicle electronic modules or wiring.
4. Poor shielding or poor connectors on antenna feed line.
5. Check for recent service bulletins detailing installation guidelines for aftermarket accessories.

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Note. Perform the following in order to avoid misdiagnosis.

1. Inspect for proper operation of brake lamps.
2. Inspect throttle linkage for mechanical binding which could cause the system to malfunction.
3. Inspect cruise control cable adjustment, should have minimum slack.
4. Refer to «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/buick/lesabre/viii-2000-2005/remont/testing-diagnostics/#engine-control-system-self-diagnostics-38l) .
5. EMI on the speed sensor signal circuit may cause erratic cruise control operation.

Conditions For Enabling Cruise Control

1. When vehicle speed is more than 40 km/h (25 mph).
2. When PARK, REVERSE, NEUTRAL, or 1st gear is not indicated.
3. When an over/undercharged battery condition does not exist.
4. With normal engine RPM.

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Removal Procedure

Note. Note the cable routing for replacement.

1. Disconnect the cruise control cable from the throttle body fuel injection cam (4).
2. Disconnect the cruise control cable from the throttle body bracket.
3. Twist the cruise control cable housing counterclockwise in order to release the cable housing from the module.
4. Disconnect the cruise control cable ball stud (1) from the actuator strip (2) on the cruise control module.
5. Remove the cable from the retainers (2). see scheme 21

Installation Procedure

1. Install the cruise control cable ball stud (1) into the slot in the cruise control module actuator strip (2). see scheme 23
2. Insert the cruise control cable housing into the cruise control module and twist clockwise to secure. NOTE: The cruise control cable does not require mechanical adjusting after the replacement. The cruise control module internally adjusts the cable. Refer to «CRUISE CONTROL DESCRIPTION & OPERATION»(/buick/lesabre/viii-2000-2005/remont/cruise-control-systems/#cruise-control-system__cruise-control-description-operation) for the complete operational details.
3. Connect the cruise control cable to the throttle body injection cam (4). see scheme 21
4. Snap the cable bracket into the throttle body bracket.
5. Install the cable into the retainers (2).

1. Disconnect the cruise control cable. Refer to «CRUISE CONTROL CABLE REPLACEMENT»(/buick/lesabre/viii-2000-2005/remont/cruise-control-systems/#cruise-control-system) .
2. Disconnect the electrical connector (2).
3. Remove the cruise control module bracket retaining fasteners (1, 3).
4. Remove the cruise control module and bracket assembly (2) from the vehicle.
5. Remove the module to bracket fasteners.
6. Remove the cruise control module from the bracket.

1. Install the cruise control module (2) to the bracket. see scheme 25 CAUTION: 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 module to bracket fasteners. Tighten the fasteners to 7.5 N.m (66 lb in).
3. Install the cruise control module and bracket assembly to the vehicle.
4. Install the module retaining fasteners (1, 3). Tighten the fasteners to 9 N.m (80 lb in).
5. Connect the electrical connector (2). see scheme 24 NOTE: The cruise control cable does not require mechanical adjusting after the replacement. The cruise control module internally adjusts the cable. Refer to «CRUISE CONTROL DESCRIPTION & OPERATION»(/buick/lesabre/viii-2000-2005/remont/cruise-control-systems/#cruise-control-system__cruise-control-description-operation) for the complete operational details.
6. Connect the cruise control cable. Refer to «CRUISE CONTROL CABLE REPLACEMENT»(/buick/lesabre/viii-2000-2005/remont/cruise-control-systems/#cruise-control-system).
7. Inspect the component operation.

CRUISE CONTROL DESCRIPTION & 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 steering wheel. The cruise control functional control switches include the ON/OFF, SET/COAST, R/A. 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 1 voltage is supplied from the cruise control 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 1 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 1 voltage is supplied through the ABS/TCC switch, to the TCC Brake switch 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, 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 0-5 volts.

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 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. Fuel cut-off.
5. When vehicle speed is too 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.
8. A 6 mph or more decrease in non-drive wheel speed in 0.4 seconds with out seeing the extended brake travel contacts of the TCC/Brake switch transition.

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:
• TESTING FOR INTERMITTENT AND POOR CONNECTIONS
• DIAGNOSTIC SYSTEM CHECK - POWER SEAT SYSTEMS
• DISABLING SYSTEM
• DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS
• DIAGNOSTIC SYSTEM CHECK - CRUISE CONTROL
• CRUISE CONTROL DESCRIPTION & OPERATION
• CHECKING AFTERMARKET ACCESSORIES