Computer/integrating Systems Buick LaCrosse I

Fastener Tightening Specifications

Fastener Tightening Specifications

Computer/Integrating Systems Schematic Icons Icon Icon Definition CAUTION: When performing service on or near the SIR components or the SIR wiring, the SIR system must be disabled. Refer to SIR DISABLING AND ENABLING ZONES . Failure to observe the correct procedure could cause deployment of the SIR components, personal injury or unnecessary SIR system repairs. IMPORTANT: Twisted-pair wires provide an effective shield that helps protect sensitive electronic components from electrical interference. In order to prevent electrical interference from degrading the performance of the connected components, you must maintain the proper specification when making any repairs to the twisted-pair wires shown : The wires must be twisted a minimum of 9 turns per 31 cm (12 in) as measured anywhere along the length of the wires. The outside diameter of the twisted wires must not exceed 6.0 mm (0.25 in)

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Body Control Module (BCM) C1

Body Control Module (BCM) C1 Connector Part Information OEM: 15448125 (Delphi) 638277-3 (AMP) Service: See Catalog 52-Way F (BK) Pin Wire Color Circuit No. Function 1 BK 860 Front Windshield Wiper Switch High Signal 2 WH 1459 Security System Sensor Supply Voltage 3 PK 1439 Ignition 1 Voltage 4 BK 28 Horn Relay Control 5 - - Not Used 6 BK 707 RAP Relay Control 7 BK/WH 1969 Headlamp High Beam Relay Control 8 D-GN/WH 1317 Fog Lamp Relay Control (T96) 9 PK/WH 1970 Headlamp Module Voltage Supply 10 WH 1080 Park Lamp Relay Control 11 YE 749 Security Indicator Control 12 GY 91 Wiper Relay Control 13 YE 196 Windshield Wiper Motor Park Switch Signal 14 BK 1835 Security System Sensor Low Reference 15 L-GN/BK 1137 DRL Ambient Light Sensor Signal 16 L-GN 526 Stop Lamp Switch Signal 17 BK 1550 Ground 18 - - Not Used 19 BK/WH 151 Ground 20 BK 1650 Ground 21 YE 5 Crank Voltage 22 PK 1239 Ignition 1 Voltage 23 BN 1141 Ignition 3 Voltage 24 TN 185 Low Washer Fluid Indicator Signal 25 WH/BK 644 12-Volt Reference 26 PK/BK 109 Hood Ajar Switch Signal (AP3) 27 GY 598 10-Volt Reference 28 BK 552 Low Reference 29 BN/WH 230 I/P Dimming Return 30 PK 1444 I/P Dimming Control 31 RD/WH 812 I/P Dimming Voltage Reference 32 BK 1576 Rear Compartment Lid Release Switch 33 BN 5077 Low Reference 34 BN/WH 1571 Traction Control Switch Signal (U68, UH8) 35 GY/BK 1598 I/P Dimming Return 36 PK/BK 1597 Courtesy Lamps Switch On Signal 37 BK/WH 1455 Keyless Entry Program Enable Signal 38 L-GN 1037 BCM Class 2 Serial Data 39 WH 17 Stop Lamp Switch Signal 40 L-GN 80 Key In Ignition Switch Signal 41 L-BU/WH 1314 Left Front Turn Signal Lamp Supply Voltage 42 D-BU/WH 1315 Right Front Turn Signal Lamp Supply Voltage 43 GY/BK 690 Courtesy Lamp Supply Voltage 44 OG 1732 Inadvertent Power Courtesy Lamp 45 - - Not Used 46 OG 340 Battery Positive Voltage 47 RD 228 Windshield Washer Pump Control 48 GY 8 Instrument Panel Lamp Supply Voltage 49 D-GN/WH 1135 A/T Shift Lock Control Solenoid Supply Voltage 50 OG 240 Battery Positive Voltage 51 OG 2440 Battery Positive Voltage 52 OG 1240 Battery Positive Voltage

Body Control Module (BCM) C2

Body Control Module (BCM) C2 Connector Part Information OEM: 15444637 (Delphi) 638277-1 (AMP) Service: See Catalog 52-Way F (BK) Pin Wire Color Circuit No. Function 1 - - Not Used 2 RD/BK 780 Driver Door Lock Switch Lock Signal 3 RD/BK 744 Rear Compartment Lid Ajar Switch 4 D-BU 245 Passenger Door Lock Switch Unlock Control 5 L-GN/BK 748 Right Rear Door Ajar Switch Signal 6 YE/BK 1181 Right Rear Door Open Switch Signal 7 L-BU/BK 747 Left Rear Door Ajar Switch Signal 8 L-GN 1177 Right Front Door Open Switch Signal 9 OG/BK 233 Park Brake Switch Signal 10 L-GN 1845 Chime Control (UD7) 11 OG/BK 781 Driver Door Lock Switch Unlock Signal 12-15 - - Not Used 16 WH 193 Rear Defog Relay Control 17 BK/WH 746 Right Front Door Ajar Switch Signal 18 D-BU/WH 1179 Left Rear Door Open Switch Signal 19 - - Not Used 20 D-GN/WH 1135 A/T Shift Lock Control Solenoid Supply Voltage 21 - - Not Used 22 L-GN 1123 Door Lock Key Switch Lock Signal 23 WH 5075 Remote Start Sensor Signal 24 PU 1124 Door Lock Key Switch Unlock Signal 25 TN 126 Left Front Door Open Switch Signal 26 GY/BK 745 Left Front Door Ajar Switch Signal 27-29 - - Not Used 30 WH 17 Stop Lamp Switch Signal 31 L-BU 244 Passenger Door Lock Switch Lock Control 32-34 - - Not Used 35 YE 2080 Driver Heated Seat Cushion Temperature Sensor Low Reference (KA1) 36 PK 2435 Passenger Heated Seat Cushion Temperature Sensor Low Reference (KA1) 37 YE/BK 2079 Heated Seat Cushion Temperature Sensor Signal (KA1) 38 GY 2434 Passenger Heated Seat Cushion Temperature Sensor Signal (KA1) 39 TN/WH 2430 Passenger Heated Seat Relay Control (KA1) 40 PU 2477 Driver Heated Seat Relay Control (KA1) 41 - - Not Used 42 L-GN 24 Backup Lamp Supply Voltage 43 YE 18 Left Rear Stop/Turn Lamp Supply Voltage 44 GY 8 Instrument Panel Lamp Supply Voltage 45 L-BU 1344 Trunk Release Control 46 TN 694 Driver Door Lock Actuator Unlock Control 47 - - Not Used 48 D-GN 19 Right Rear Stop/Turn Lamp Supply Voltage 49 OG 440 Battery Positive Voltage 50 BK 550 Ground 51 TN 294 Door Lock Actuator Unlock Control 52 GY 295 Door Lock Actuator Lock Control

Body Control Module (BCM) C3

Body Control Module (BCM) C3 Connector Part Information OEM: 638397-1 (AMP) 15383281 (Delphi) Service: See Catalog 18-Way F Unsealed (BK) Pin Wire Color Circuit No. Function 1-3 - - Not Used 4 L-BU/WH 1414 Left Turn Signal Switch Signal 5 L-BU 1714 Windshield Washer Switch Low Signal 6 D-BU 658 Cellular Telephone Voice Signal 7 WH 103 Headlamp Switch Headlamps On Signal 8 BN/WH 301 Park Lamp Switch On Signal 9 - - Not Used 10 L-BU 1872 Exterior Lamps Off Input 11 OG 192 Front Fog Lamp Switch Signal 12 PU 524 Headlamp Dimmer Switch High Beam Signal 13 PK 94 Windshield Washer Switch Signal 14 BN 1356 Flash To Pass Switch Signal 15 BK/WH 1251 Ground 16 TN 2144 Hazard Switch Signal 17 D-BU/WH 1415 Right Turn Signal Switch Signal 18 L-GN 1715 Windshield Washer Switch High Signal

Data Link Connector (DLC)

Data Link Connector (DLC) Connector Part Information OEM: 15488184 Service: See Catalog 16-Way F Metri-Pack 150 Series (BK) Pin Wire Color Circuit No. Function 1 - - Not Used 2 PU 1132 DLC Class 2 Serial Data 3 - - Not Used 4 BK 1450 Ground 5 BK/WH 1551 Ground 6 YE 2361 SAE J1939 Serial Data (+) (LY7) 7-13 - - Not Used 14 D-GN 2362 SAE J1939 Serial Data (-) (LY7) 15 - - Not Used 16 OG 2340 Battery Positive Voltage

Splice Pack SP205

Splice Pack SP205 Connector Part Information OEM: 15450641 Service: See Catalog 12-Way F GT 150 Series (GY) Pin Wire Color Circuit No. Function A PU 1132 DLC Class 2 Serial Data B D-GN 1049 ECM/PCM Class 2 Serial Data C - - Not Used D OG 1044 Radio Class 2 Serial Data E L-BU 1122 ABS/TCS Class 2 Serial Data F D-BU 1128 SDM Class 2 Serial Data G GY 1036 IPC Class 2 Serial Data H - - Not Used J L-GN 2271 ADG Class 2 Serial Data (UE1) K - - Not Used L WH 1038 HVAC Class 2 Serial Data M L-GN 1037 BCM Class 2 Serial Data

DIAGNOSTIC CODE INDEX

DIAGNOSTIC CODE INDEX

Begin the system diagnosis with Diagnostic System Check - Vehicle in Vehicle DTC Information. The Diagnostic System Check - Vehicle will provide the following information

1. The identification of the control modules which are not communicating.
2. The identification of any stored diagnostic trouble codes (DTCs) and their status.

The use of the Diagnostic System Check - Vehicle will identify the correct procedures to begin vehicle diagnosis. These must be performed before system DTC or symptom diagnosis.

Scan Tool Output Controls

Scan Tool Output Controls

Scan Tool Data List

Scan Tool Data List

Circuit Description

The internal fault detection is handled inside the control module. No external circuits are involved.

DTC Descriptor

This diagnostic procedure supports the following DTC

DTC B1000 Electronic Control Unit (ECU) Performance

Conditions for Running the DTC

The microprocessor runs the program to detect an internal fault when power up is commanded. The only requirements are voltage and ground. This program runs even if the voltage is out of the valid operating range.

Conditions for Setting the DTC

1. The control module detects an internal write malfunction.
2. The control module detects an internal checksum malfunction.

Action Taken When the DTC Sets

The microprocessor refuses all additional inputs.

Conditions for Clearing the DTC

1. A current DTC clears when the malfunction is no longer present.
2. A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.

Diagnostic Aids

1. This DTC may be stored as a history DTC without affecting the operation of the module. If stored only as a history DTC and not retrieved as a current DTC, do not replace the module.
2. If this DTC is retrieved as both a current and history DTC, replace the module.

DTC B1000

Some control modules must be configured with serial numbers, vehicle options or other information. If a control module was not properly configured after installation, that module may set DTC B1001.

This diagnostic procedure supports the following DTC

DTC B1001 Option Configuration Error

The ignition is ON.

The control module is not configured properly.

1. The SERVICE VEHICLE SOON indicator illuminates.
2. The check gages chime sounds.

1. A current DTC B1001 will clear when the module is correctly programmed.
2. A history DTC B1001 will clear after the ignition has been cycled 100 times, without a repeat of the malfunction.

The most likely reasons for DTC B1001 being set are incorrect calibration files were downloaded to the module or the module was replaced without the recalibration having been performed.

Test Description

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

1. 3: If DTC B1001 is set as current, reprogram the module.

DTC B1001

The internal fault detection is handled inside the control module. No external circuits are involved.

This diagnostic procedure supports the following DTC

DTC B1004 Electronic Control Unit Identification Circuit

The module microprocessor must be active/awake.

This DTC indicates the keep alive memory (KAM) in the module has been reset. It is a normal occurrence when battery positive voltage or ground is removed from the module, such as a battery disconnect.

The microprocessor reverts back to the base programmed critical operating data until new data is learned and stored in KAM.

1. A current DTC clears when the malfunction is no longer present.
2. A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.

1. This DTC may be stored as a history DTC without affecting the operation of the module. If stored only as a history DTC and not retrieved as a current DTC, do not replace the module.
2. If this DTC is retrieved as both a current and history DTC, replace the module.

DTC B1004

As part of normal data processing, the module performs a data programming check on its writes to the electrically erasable programmable read only memory (EEPROM). The EEPROM write error detection is handled inside the control module. No external circuits are involved.

This diagnostic procedure supports the following DTC

DTC B1007 EEPROM Read/Write Error

The module runs the program to detect an EEPROM write error. The only requirements are battery positive voltage and ground. This program runs even if the battery positive voltage is out of the valid operating range.

The module writes information to a data block in the EEPROM. The module then reads the data and compares it to what was sent to the data block. If the data does not match after 3 consecutive attempts, the module sets the DTC.

The module writes to another area of the EEPROM, this becomes the new permanent area to store the data. The data location is allowed to change until all of the available EEPROM is used. If a DTC B1004 is also set, the module reverts to base operation values programmed for those blocks of data that have failed. The blocks of data that have not failed the checksum test are not affected.

1. A current DTC clears when the malfunction is no longer present.
2. A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.

1. This DTC may be stored as a history DTC without affecting the operation of the module. If stored only as a history DTC and not retrieved as a current DTC, do not replace the module.
2. If this DTC is retrieved as both a current and history DTC, replace the module.

DTC B1007

The electrically erasable programmable read-only memory (EEPROM) checksum error detection is handled inside the control module. No external circuits are involved.

This diagnostic procedure supports the following DTC

DTC B1009 EEPROM Checksum Mismatch

The module runs the program to detect an EEPROM checksum error after each wake-up. The only requirements are battery positive voltage and ground. This program runs even if the voltage is out of the valid operating range.

The module retains an inverse copy of the digital value stored in certain blocks of memory in the EEPROM. The module then reads the information from those certain blocks and adds the stored inverse value to the current value. If they do not equal 0, the module sets the DTC.

The module reverts to base operation values programed for those blocks of data that have failed the checksum test. The blocks of data that have not failed the checksum test are not affected.

1. A current DTC clears when the malfunction is no longer present.
2. A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.

1. This DTC may be stored as a history DTC without affecting the operation of the module. If stored only as a history DTC and not retrieved as a current DTC, do not replace the module.
2. If this DTC is retrieved as both a current and history DTC, replace the module.

DTC B1009

This test checks the validity of the module FLASH memory calibration values. Error detection is performed inside the control module. no external circuits are involved.

This diagnostic procedure supports the following DTC

DTC B1013 Calibration Read Only Memory (ROM) Checksum Error

The module runs the program to detect a FLASH calibration error after each wake-up. The only requirements are battery positive voltage and ground.

The module retains a copy of the FLASH calibration checksum reference value in the FLASH memory. During wake-up the module shall compute the FLASH calibration value and compare it to the FLASH calibration checksum reference value. If the 2 values do not match the module sets this DTC.

The module may have limited functional operation depending on the severity of the FLASH calibration corruption. The module physical operation will allow for the module to be reprogrammed to correct the malfunction.

1. A current DTC clears when the malfunction is no longer present.
2. A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.

The following are most likely cause for this DTC being set

1. Incorrect files downloaded to the module.
2. A module installed in the vehicle without the reprogramming procedure having been performed.

DTC B1013

This test checks the validity of the module FLASH memory application values. Error detection is performed inside the control module. No external circuits are involved.

This diagnostic procedure supports the following DTC

DTC B1014 Program Read Only Memory (ROM) Checksum Error

The module runs the program to detect a FLASH application error after each wake-up. The only requirements are battery positive voltage and ground.

The module retains a copy of the FLASH application checksum reference value in the FLASH memory. During wake-up the module shall compute the FLASH application value and compare it to the FLASH application checksum reference value. If the 2 values do not match the module sets this DTC.

The module will enter boot mode when this DTC sets. In boot mode, only the program FLASH memory function will be available.

1. A current DTC clears when the malfunction is no longer present.
2. A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.

The following are most likely cause for this DTC being set

1. Incorrect files downloaded to the module.
2. A module installed in the vehicle without the reprogramming procedure having been performed.

DTC B1014

The body control module (BCM), monitors the ignition inputs OFF, ignition 3, crank and ignition 1 supplied from the ignition switch. The BCM uses the sequence that the signals appear and their voltage levels to determine the power mode called for by the vehicle operator using the ignition switch. A 12-volt reference voltage is supplied by the BCM to the ignition switch over a discrete circuit. The ignition switch uses this voltage for power mode signal discrimination. When the operator places the ignition switch in the Run or Start position, the ignition 1 circuit is delivers the signal to the BCM.

This diagnostic procedure supports the following DTC

DTC B1370 Device Ignition 1 (ON and START) Circuit

1. The BCM must be powered and must detect a change in the ignition switch circuit states.
2. The vehicle battery must be fully charged.

The BCM detects that the ignition 1 signal is shorted to ground, voltage or open for more than 10 seconds in the current ignition cycle.

1. The BCM stores DTC to memory.
2. The BCM operates in a fail-safe power mode dependent on the last valid power mode detected and the state of the engine run flag data on the class 2 serial data communications circuits.
3. The other modules on the vehicle operate in a fail safe power mode dependent on the last valid power mode transmitted by the BCM and the state of the engine run flag on the class 2 serial data communications circuits.

1. A current DTC clears on the next malfunction-free cycle.
2. A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.

A history DTC maybe caused by an intermittent short or open in the ignition 1 circuit. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

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

1. 3: This step tests the ignition switch for a short circuit between the 12-volt reference supply circuit and the ignition 1 circuit in the OFF position.
2. 4: This step tests the wiring of the ignition 1 circuit for a short to ground or voltage.
3. 5: This step tests the ignition switch for a closed circuit between the ignition switch 12-volt reference supply circuit and the ignition 1 circuit in the Run and Crank switch positions. Care must be taken as the engine may crank during this test.

DTC B1370

The body control module (BCM) monitors the ignition inputs OFF, ignition 3, crank and ignition 1 supplied from the ignition switch. The BCM uses the sequence that the signals appear and their voltage levels to determine the power mode called for by the vehicle operator using the ignition switch. A 12-volt reference voltage is supplied by the BCM to the ignition switch over a discrete circuit. The ignition switch uses this voltage for power mode signal discrimination. When the operator places the ignition switch in the Run or Accessory position, the ignition 3 circuit delivers the signal to the BCM.

This diagnostic procedure supports the following DTC

DTC B1380 Device Ignition ACCESSORY Circuit

1. The BCM must be powered and must detect a change in the ignition switch circuit states.
2. The vehicles battery must be fully charged.

The BCM detects that the ignition 3 signal is shorted to ground, voltage or open for more than 10 seconds in the current ignition cycle.

1. The BCM stores DTC to memory.
2. The BCM operates in a fail-safe power mode dependent on the last valid power mode detected and the state of the engine run flag data on the class 2 serial data communications circuits.
3. The other modules on the vehicle operate in a fail safe power mode dependent on the last valid power mode transmitted by the BCM and the state of the engine run flag on the class 2 serial data communications circuits.

1. A current DTC clears on the next malfunction-free cycle.
2. A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.

A history DTC maybe caused by an intermittent short or open in the ignition 3 circuit. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

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

1. 3: This step tests the ignition switch for a short circuit between the 12-volt reference supply circuit and the ignition 3 circuit in the OFF position.
2. 4: This step tests the wiring of the ignition 3 circuit for a short to ground or voltage.
3. 5: This step tests the ignition switch for a closed circuit between the ignition switch 12-volt reference supply circuit and the ignition 3 circuit in the Run and Crank switch positions. Care must be taken as the engine may crank during this test.

DTC B1380

The body control module (BCM), monitors the ignition inputs OFF, ignition 3, crank and ignition 1 supplied from the ignition switch. The BCM uses the sequence that the signals appear and their voltage levels to determine the power mode called for by the vehicle operator using the ignition switch. A 12-volt reference voltage is supplied by the BCM to the ignition switch over a discrete circuit. The ignition switch uses this voltage for power mode signal discrimination. When the operator places the Ignition switch in the Start position, the Crank circuit delivers the signal to the BCM.

This diagnostic procedure supports the following DTC

DTC B1385 Device Ignition START Circuit

1. The BCM must be powered and must detect a change in the ignition switch circuit states.
2. The vehicles battery must be fully charged.

The BCM detects that the crank signal is shorted to ground, voltage or open for more than 10 seconds in the current ignition cycle.

1. The BCM stores DTC to memory.
2. The engine will not crank.
3. The BCM operates in a fail-safe power mode dependent on the last valid power mode detected and the state of the engine run flag data on the class 2 serial data communications circuits.
4. The other modules on the vehicle operate in a fail safe power mode dependent on the last valid power mode transmitted by the BCM and the state of the engine run flag on the class 2 serial data communications circuits.

1. A current DTC clears on the next malfunction free cycle.
2. A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.

A history DTC maybe caused by an intermittent short or open in the crank circuit. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

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

1. 3: This tests the ignition switch for a short circuit between the 12-volt reference supply circuit and the crank circuit in the OFF position.
2. 4: This tests the wiring of the crank circuit for a short to ground or voltage.
3. 5: This tests the ignition switch for a closed circuit between the ignition switch 12-volt reference supply circuit and the crank circuit in the Crank switch position. Care must be taken as the engine may crank during this test.

DTC B1385

The body control module (BCM) has an internal battery voltage sensor and a reference voltage. The BCM compares these 2 voltages via the 2 battery positive voltage circuits every 300 milliseconds.

This diagnostic procedure supports the following DTC

DTC B1390 Device Voltage Reference Input Circuit

This DTC will run only if the BCM has power and ground. This DTC will execute regardless of the source voltage.

This code shall be set after 10 consecutive readings that the 2 battery positive voltages differ by one volt or greater.

All writes to the electrically erasable programmable read only memory (EEPROM) will be suspended. All loss of communication and low/high voltage DTC codes are suspended.

1. A current DTC clears when the malfunction is no longer present.
2. A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.

DTC B1390

The body control module (BCM) controls various accessories through the retained accessory power (RAP) relay circuit. When the ignition switch is in either the ACC or the ON position, the BCM provides battery negative voltage to the RAP relay control circuit. When the RAP relay is energized, it supplies a B+ to the accessories not controlled by a serial data power mode message.

When the ignition switch turns from ON or ACC to OFF, with all of the vehicle doors closed, the BCM keeps the relay energized for 10 minutes or until any vehicle door opens.

This diagnostic procedure supports the following DTC

DTC B1475 Retained Accessory Power Circuit

The system voltage must be between 9-16 volts.

1. The BCM detects a short to voltage in the RAP relay control circuit when the BCM is trying to energize the relay.
2. The BCM detects that the RAP relay control circuit is open.
3. The condition above must be present for more than 1 second.

1. The BCM stores DTC B1475 in memory.
2. The devices powered by the RAP supply voltage circuit will not operate.

1. A current DTC clears when the malfunction is no longer present.
2. A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.

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

1. 2: Listen for an audible click when the RAP relay operates. Command both the ON and OFF states. Repeat the commands, as necessary.
2. 3: This step tests for voltage at the coil side of the RAP relay. The RAP fuse supplies power to the coil side of the RAP relay.
3. 4: This step verifies that the BCM is providing ground to the RAP relay.
4. 5: This step tests the control circuit side of the RAP relay for faults that cause both B1475 RAP DTC.
5. 10: After replacement of the BCM you must calibrate the new module for proper operation.

DTC B1475

The internal fault detection is handled inside the control module. No external circuits are involved.

This diagnostic procedure supports the following DTC

DTC C0550 Electronic Control Unit (ECU) Performance

The microprocessor runs the program to detect an internal fault when power up is commanded. The only requirements are voltage and ground. This program runs even if the voltage is out of the valid operating range.

1. The control module detects an internal write malfunction.
2. The control module detects an internal checksum malfunction.

If equipped, the following module specific actions may occur

1. The ABS indicator turns on.
2. The BRAKE Warning indicator turns on.
3. The SERVICE 4WD indicator turns on and the system will be disabled.
4. The Service 4 Wheel Steering indicator turns on and the system will be disabled.
5. The SERVICE RIDE SYS or SERVICE RIDE CONTROL message is displayed.
6. The SERVICE SUSPENSION SYS message is displayed.
7. The traction control system (TCS) indicator turns ON.

1. A current DTC clears when the malfunction is no longer present.
2. A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.

1. This DTC may be stored as a history DTC without affecting the operation of the module. If stored only as a history DTC and not retrieved as a current DTC, do not replace the module.
2. If this DTC is retrieved as both a current and history DTC, replace the module.

DTC C0550

The ignition 1 relay is controlled by the body control module (BCM). The ignition 1 relay contacts are supplied a hot at all times from the fuse block underhood. The relay supplies power to several components when the vehicle is in the RUN or CRANK power mode. When the ignition switch is placed in the RUN or CRANK position, the BCM will receive an ignition 1 signal from the ignition switch and turn ON the ignition 1 relay. When the ignition switch is in the OFF position, the BCM will turn OFF the ignition 1 relay. The powertrain control module (PCM) compares the ignition 1 relay output signal with the BCM class 2 serial data power mode message. If the ignition 1 voltage signal and the power mode message do not match for an allotted time, the PCM will disable the fuel injectors and DTC P2535 will set.

This diagnostic procedure supports the following DTC

DTC P2535 Ignition 1 Switch Circuit High Voltage

1. The vehicle is in PARK or NEUTRAL.
2. The ignition switch is OFF.

The ignition 1 voltage signal is higher than normal for more than 7 seconds.

1. The control module stores the DTC information into memory when the diagnostic runs and fails.
2. The malfunction indicator lamp (MIL) will not illuminate.
3. The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records.
4. The driver information center, if equipped, may display a message.

1. A current DTC Last Test Failed clears when the diagnostic runs and passes.
2. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.
3. Clear the DTC with a scan tool.

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

1. 8: This relay may be a permanently integrated in the BEC on some vehicles, in this case you must replace the BEC in order to complete the repair.

DTC P2535

Modules connected to the GMLAN serial data circuit monitor for serial data communications on the GMLAN network during normal vehicle operation. Operating information and commands are exchanged among the modules. Each module on GMLAN network maintains a transmit error counter (TEC) and a receive error counter (REC). The counter values increase with detected errors and will decrease with error-free messages. If the TEC value exceeds 255 the controller removes itself from the network and a DTC U0001 will be set.

This diagnostic procedure supports the following DTC

DTC U0001 High Speed CAN Communication Bus

This vehicle has DTCs which include DTC Symptoms. For more information on DTC Symptoms, refer to Symptoms - Vehicle in Vehicle DTC Information.

DTC U0001

Conditions for Running the DTCs

1. Voltage supplied to the module is in the normal operating voltage range.
2. The vehicle power mode requires serial data communication to occur.

A certain number of no valid transmitted messages on the GMLAN serial data circuits are detected by the module.

Action Taken When the DTCs Sets

1. The module suspends all message transmission.
2. The module uses default values for all parameters received on the GMLAN serial data circuits.
3. The module inhibits the setting of all other GMLAN communication DTCs.

1. A current DTC clears when the malfunction is no longer present.
2. A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.

1. This DTC cannot be retrieved with a current status. Diagnosis of current DTC is accomplished via the symptom, Scan Tool Does Not Communicate with GMLAN Device. Refer to «Scan Tool Does Not Communicate with High Speed GMLAN Device»(/buick/lacrosse/i-2004-2009/remont/communication-devices/#computerintegrating-systems__scan-tool-does-not-communicate-with) .
2. An intermittent condition is likely to be caused by a short on the GMLAN serial data circuits. Use the Scan Tool Does Not Communicate with GMLAN Device procedure in order to isolate an intermittent condition. Refer to «Scan Tool Does Not Communicate with High Speed GMLAN Device»(/buick/lacrosse/i-2004-2009/remont/communication-devices/#computerintegrating-systems__scan-tool-does-not-communicate-with) .

Modules connected to the high speed GMLAN serial data circuits monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules. The modules have prerecorded information about what messages are needed to be exchanged on the serial data circuits, for each virtual network. The messages are supervised and also, some periodic messages are used by the receiver module as an availability indication of the transmitter module. The supervision time-out period is 250 ms. Each message contains the identification number of the transmitter module.

DTC Descriptors

This diagnostic procedure supports the following DTCs

1. DTC U0100 Lost Communication With Engine Control Module (ECM)
2. DTC U0101 Lost Communication With Transmission Control Module (TCM)

1. Voltage supplied to the modules is in the normal operating voltage range.
2. The vehicle power mode requires serial data communication to occur.
3. The DTC U0001 does not have a current status.

A supervised periodic message that includes the transmitter module availability has not been received.

The module uses a default value for the missing parameter.

1. A current DTC clears when the malfunction is no longer present.
2. A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.

1. A poor connection at the inoperative module may cause this code to set.
2. An improperly powered module may cause this code to set.

DTC U0100-U0299

Modules connected to the class 2 serial data circuit monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules. When a module receives a message for a critical operating parameter, the module records the identification number of the module which sent the message for state of health (SOH) monitoring. A critical operating parameter is one which, when not received, requires that the module use a default value for that parameter. When a module does not associate an identification number with at least one critical parameter within about 5 seconds of beginning serial data communication, DTC U1000 or U1255 is set. If more than one critical parameter does not have an identification number association, the DTC will only be reported once.

This diagnostic procedure supports the following DTCs

1. DTC U1000 Class 2 Data Link Malfunction
2. DTC U1255 Lost Communications

1. Voltage supplied to the module is in the normal operating voltage range of 9-16 volts.
2. Diagnostic trouble codes U1300, U1301 and U1305 do not have a current status.
3. The module operation or the vehicle power mode requires serial data communication to occur.

At least one critical operating parameter has not been associated with an identification number within about 5 seconds after beginning serial data communication.

The module uses a default value for the missing parameter.

1. A current DTC U1000 will clear when all critical operating parameters for the module have been associated with an identification number or at the end of the current ignition cycle.
2. A history DTC U1000 will clear after 50 ignition switch ON/OFF cycles with no repeat of the failure.

When a malfunction, such as an open fuse to a module occurs while modules are communicating, a Lost Communication DTC for a specific module is set as a current DTC. When the modules stop communicating, the current Lost Communication DTC is cleared, but the history DTC remains. When the modules begin to communicate again, the module with the open fuse will not be learned by the other modules, so DTC U1000 is set current by the other modules. If the malfunction occurs when the modules are not communicating, only DTC U1000 or U1255 is set.

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

1. 1: A Lost Communication with XXX DTC with a history status may indicate the cause of U1000.
2. 2: The module that is not communicating is the likely cause of U1000 or U1255 being set.
3. 5: The module which was not communicating may have set Lost Communication with XXX DTCs for those modules that it was monitoring.
4. 6: The module which was not communicating may have set Lost Communication with XXX DTCs for those modules that it was monitoring.
5. 7: The module that was not communicating may have set Lost Communication with XXX DTCs for those modules that the module was monitoring.
6. 11: The modules that communicate indicate the module that cannot communicate. You must clear the DTC from the modules in order to avoid future misdiagnosis.
7. 13: If all modules are communicating, the module that set U1000 may have done so due to some other condition.
8. 14: The module that set U1000 is the likely cause of the malfunction.

DTC U1000 and U1255

Modules connected to the class 2 serial data circuit monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules. When a module receives a message for a critical operating parameter, the module records the identification number of the module which sent the message for State of Health monitoring (Node Alive messages). A critical operating parameter is one which, when not received, requires that the module use a default value for that parameter. Once an identification number is learned by a module, it will monitor for that modules "Node Alive" message. Each module on the class 2 serial data circuit which is powered and performing functions that require detection of a communications malfunction is required to send a "Node Alive" message every 2 seconds. When no message is detected from a learned identification number for 5 seconds, a DTC U1xxx, where xxx is equal to the 3 digit identification number, is set.

The Control Module ID Number list provides a method for determining which module is not communicating. A module with an internal class 2 serial data circuit malfunction or which loses power during the current ignition cycle would have a Lost Communication DTC set by other modules. The modules that can communicate will set a DTC indicating the module that cannot communicate. When no message is detected from a learned identification number for five seconds, a DTC U1xxx, where xxx is equal to the 3 digit identification number, is set.

This diagnostic procedure supports the following DTC

DTC U1XXX Lost communication With XXX Module

DTC U1001-U1254

When more than one Loss of Communication DTC is set in either one module or in several modules, diagnose the DTCs in the following order

1. Current DTCs before history DTCs unless told otherwise in the diagnostic tables.
2. The DTC which is reported the most times.
3. From the lowest number DTC to the highest number DTC.

1. Voltage supplied to the module is in the normal operating voltage range of 9-16 volts.
2. Diagnostic trouble codes U1300, U1301 and U1305 do not have a current status.
3. The vehicle power mode, ignition switch position, requires serial data communication to occur.

A message from a learned identification number has not been detected for the past 5 seconds.

1. A current DTC clears when the malfunction is no longer present.
2. A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.

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

1. 1: A module which loses power during an ignition cycle will cause other modules to set Lost Communication DTCs.
2. 2: A module which loses ground during an ignition cycle will cause other modules to set Lost Communication DTCs.
3. 3: The malfunction is due to an open in the class 2 serial data circuit or an open in the module.
4. 7: The module which was not communicating may have set Lost Communication DTCs for those modules that it was monitoring.
5. 9: The modules which can communicate indicate the module which cannot communicate. You must clear the DTCs from these modules to avoid future misdiagnosis.

DTC U1001-U1254

Modules connected to the class 2 serial data circuit monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules. In addition to this, Node Alive messages are transmitted by each module on the class 2 serial data circuit about once every 2 seconds. When the module detects one of the following conditions on the class 2 serial data circuit for approximately 3 seconds, the setting of all other class 2 serial communication DTCs is inhibited and a DTC will set.

DTC U1300, U1301 or U1305

This diagnostic procedure supports the following DTCs

1. DTC U1300 Class 2 Data Link Low
2. DTC U1301 Class 2 Data Link High
3. DTC U1305 Class 2 Data Link Low or High

1. Voltage supplied to the module is in the normal operating voltage range.
2. The vehicle power mode requires serial data communication to occur.

Conditions for Setting the DTCs

1. No valid messages are detected on the class 2 serial data circuit.
2. The voltage level detected on the class 2 serial data circuit is in one of the following conditions: High Low
3. The above conditions are met for approximately 3 seconds.

The module uses default values for all parameters received on the class 2 serial data circuit.

1. A current DTC clears when the malfunction is no longer present.
2. A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.

1. These DTCs cannot be retrieved with a current status. Diagnosis of current DTCs is accomplished via the symptom, Scan Tool Does Not Communicate with a Class 2 Device. Refer to «Scan Tool Does Not Communicate with Class 2 Device»(/buick/lacrosse/i-2004-2009/remont/communication-devices/#computerintegrating-systems) .
2. An intermittent condition is likely to be caused by a short on the class 2 serial data circuit. Use the Scan Tool Does Not Communicate with a Class 2 Device procedure in order to isolate an intermittent condition. Refer to «Scan Tool Does Not Communicate with Class 2 Device»(/buick/lacrosse/i-2004-2009/remont/communication-devices/#computerintegrating-systems) .

The GMLAN serial data circuits are controller area network (CAN) high speed serial data buses used to communicate information between the control modules. Typical data transmission speeds must be high enough to ensure that a required real-time response is maintained. On this vehicle there are 2 utterly different types of GMLAN serial data circuits, the High speed 2-wire circuit and Low speed single wire circuit. Refer to Data Link Communications Description and Operation for the complete description of these buses. The GMLAN serial data circuits also communicate directly to the DLC connector. Messages are interpreted by the externally connected CANdi module which acts as a transceiver for the scan tool.

Modules connected to the GMLAN serial data circuits monitor communications during normal vehicle operation, where operation information is exchanged among the modules. All the modules on the GMLAN networks, maintain a transmit error counter (TEC) and a receive error counter (REC). The counter values increase with detected errors and will decrease with error-free messages. If the TEC value exceeds 255, the controller removes itself from the network and DTC U0073 will result.

This diagnostic procedure supports the following DTC

DTC U2100 Controller Area Network (CAN) Bus Communication

1. Supply voltage to the modules are in the normal operating range.
2. The vehicle is in the RUN power mode.

The module setting the DTC has attempted to establish communications on the GMLAN circuits for more than 7 times.

1. The module suspends all message transmission.
2. The module uses default values for all parameters received on the serial data circuits.
3. The module inhibits the setting of all other communication DTCs.

1. A current DTC clears when the malfunction is no longer present.
2. A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.

1. This DTC cannot be retrieved with a current status. Diagnosis of a current DTC is accomplished via the symptom, Scan Tool Does Not Communicate with High Speed GMLAN Device. Refer to «Data Link References»(/buick/lacrosse/i-2004-2009/remont/communication-devices/#computerintegrating-systems__data-link-references) for the correct procedure for the specific module(s).
2. An intermittent condition is likely to be caused by a short on the GMLAN serial data circuits. Use the Scan Tool Does Not Communicate with High Speed GMLAN Device procedure in order to isolate an intermittent condition. Refer to «Data Link References»(/buick/lacrosse/i-2004-2009/remont/communication-devices/#computerintegrating-systems__data-link-references) for the correct procedure for the specific modules.

Modules connected to the GMLAN serial data circuits monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules. The modules have programmed information about what messages are needed to be exchanged on the serial data circuits, for each virtual network. The messages are also supervised and some periodic messages are used by the receiver module as an availability indication of the transmitter module. The supervision time-out period is 250 milliseconds. Each message contains the identification number of the transmitter module. When a message that indicates the availability of the transmitter module is not received, the receiver module sets a DTC 21xx where xx is equal to the 2-digit identification number of the transmitter module.

The DTC descriptors listed below provide a method for determining which module is not communicating. A module with a GMLAN serial data circuit malfunction or which loses power during the current ignition cycle will have a Loss of Communication DTC set by other modules that depend on information from that failed module. The modules that can communicate will set a DTC indicating the module that cannot communicate.

This diagnostic procedure supports the following DTCs

1. DTC U2105 Lost Communications With Engine Control System
2. DTC U2107 Lost Communications With Body Control System
3. DTC U2108 Lost Communications With ABS/TCS Control System

When more than one Loss of Communication DTC is set in either one module or in several modules, diagnose the DTCs in the following order

1. Current DTCs before history DTCs unless told otherwise in the diagnostic table.
2. The DTC which is reported the most times.

1. Voltage supplied to the modules is in the normal operating voltage range.
2. The vehicle power mode requires serial data communication to occur.
3. DTC U2100, U0073 or U1000 does not have a current status.

A supervised periodic message that includes the transmitter module availability has not been received.

The module uses a default value for the missing parameter.

1. A current DTC clears when the malfunction is no longer present.
2. A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.

1. A poor connection at the inoperative module may cause this code to set.
2. An improperly powered module may cause this code to set.

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

1. 3: If body control module (BCM) will not power up the vehicle cannot establish the correct power mode. This step tests for the correct power supply conditions for the BCM.
2. 4: If DTC U2105 to U2177 are set as history and you can communicate with the suspect module, the malfunction is an intermittent communication buss, power supply, ground or internal module connection.
3. 5: This step tests for the correct power supply conditions of the suspect module or modules.
4. 7: The malfunction is in the Class 2 serial data circuit and not in the GMLAN high speed circuit.
5. 8: This step identifies which of the GMLAN busses the module or modules use for communication. Use the «Data Link References»(/buick/lacrosse/i-2004-2009/remont/communication-devices/#computerintegrating-systems__data-link-references) for identifying the correct buss to analyze.
6. 13: The module which was not communicating due to an open in the GMLAN serial data circuits may have set Loss of Communication DTCs for those modules that it was monitoring.
7. 14: The modules which can communicate indicate the module which cannot communicate. You must clear the DTC from these modules to avoid future misdiagnosis.

DTC U2105-U2199

1. Perform the «Diagnostic System Check - Vehicle»(/buick/lacrosse/i-2004-2009/remont/oem-general-information/#vehicle-dtc-information) in Vehicle DTC Information 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 links.
2. Review the system operation in order to familiarize yourself with the system functions. Refer to: «Data Link Communications Description and Operation»(/buick/lacrosse/i-2004-2009/remont/communication-devices/#computerintegrating-systems) «Body Control System Description and Operation»(/buick/lacrosse/i-2004-2009/remont/communication-devices/#computerintegrating-systems__body-control-system-description-and-operation) «Retained Accessory Power (RAP) Description and Operation»(/buick/lacrosse/i-2004-2009/remont/communication-devices/#computerintegrating-systems)

Visual/Physical Inspection

1. Inspect for aftermarket devices which could affect the operation of the systems. Refer to «Checking Aftermarket Accessories»(/buick/lacrosse/i-2004-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing__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 Conditions and Poor Connections in Wiring Systems.

Symptom List

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

1. «Scan Tool Does Not Power Up»(/buick/lacrosse/i-2004-2009/remont/communication-devices/#computerintegrating-systems)
2. «Scan Tool Does Not Communicate with Class 2 Device»(/buick/lacrosse/i-2004-2009/remont/communication-devices/#computerintegrating-systems)
3. «Scan Tool Does Not Communicate with High Speed GMLAN Device»(/buick/lacrosse/i-2004-2009/remont/communication-devices/#computerintegrating-systems__scan-tool-does-not-communicate-with)

The data link connector (DLC) is a standardized 16 cavity connector. Connector design and location is dictated by an industry wide standard and is required to provide the following

1. Scan tool power battery positive voltage at terminal 16
2. Scan tool power ground at terminal 4
3. Common signal ground at terminal 5

The scan tool will power up with the ignition OFF. Some modules, however, will not communicate unless the ignition is ON and the power mode master (PMM) module sends the appropriate power mode message.

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

1. 4: If the battery positive voltage and ground circuits of the DLC are functioning properly. The malfunction must be due to the scan tool.

Scan Tool Does Not Power Up

Modules connected to the class 2 serial data circuit monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules. Connecting a scan tool to the data link connector (DLC) allows communication with the modules for diagnostic purposes. DTCs may be set due to this symptom and during this diagnostic procedure. Complete the diagnostic procedure in order to ensure all the DTCs are diagnosed and cleared from memory.

1. The body control module (BCM) detects that the ignition is ON and sends the appropriate power mode message to the other modules. Therefore, the BCM must be connected to the DLC for any other module to communicate with the scan tool.
2. When the class 2 serial data circuit is shorted to ground or to voltage, the following DTCs may set: U1300 U1301 U1305

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

1. 2: A partial loss of communication in the class 2 serial data circuit uses a different procedure than a total loss of communication of the class 2 serial data circuit.
2. 4: The following DTCs may be retrieved with a history status. These DTCs are not the cause of the present condition. U1300 U1301 U1305
3. 6: A State of Health DTC with a history status may be present along with a U1000 or U1255 with a current status. This indicates that the malfunction occurred when the ignition was ON.
4. 10: Normal class 2 serial data communication cannot take place until the power mode master (PMM) module sends the appropriate power mode message. If the PMM does not send a wake-up message, other modules on the class 2 serial data circuit may not communicate.
5. 12: This step uses the loss of communications with a class 2 serial data circuit to locate the probable malfunction. On vehicles equipped with a digital radio receiver (DRR), the DRR must be isolated from the sensing and diagnostic module (SDM) to evaluate the condition of that class 2 serial data circuit branch. The following modules communicate on the class 2 serial data circuit: Driver information center (DIC) DRR Electronic brake control module (EBCM) Instrument panel cluster (IPC) Head-up display (HUD) HVAC Powertrain control module (PCM) Radio Vehicle communication interface module (VCIM) SDM
6. 17: If there are no current DTCs that begin with the letter "U", the communication concern has been repaired.
7. 18: The communication concern may have prevented diagnosis of the customer complaint.

Scan Tool Does Not Communicate with Class 2 Device

Scan Tool Does Not Communicate with High Speed GMLAN Device

Modules connected to the GMLAN serial data circuit monitor for serial data communications on the GMLAN network during normal vehicle operation. Operating information and commands are exchanged among the modules. When a module detects a bus-off condition a DTC U2100 will be set. This DTC can be retrieved as history only.

The engine will not start when there is a total malfunction of the GMLAN serial data circuits while the engine is not running. The following conditions may cause a total loss of GMLAN data communication

1. Any of the serial data circuits shorted to ground.
2. Any of the serial data circuits shorted to voltage.
3. A short between serial data circuits.
4. An internal malfunction of a module on the GMLAN network that causes a short to voltage or ground.

Scan Tool Does Not Communicate with High Speed GMLAN Device

Normal vehicle serial data communications and module operations will not begin until the system power mode has been identified. Discrete wires from the ignition switch contacts are monitored by a module which acts as the power mode master (PMM) in order to determine the correct power mode. The module which is the PMM communicates the system power mode to all modules on the serial data lines. Refer to Body Control System Description and Operation to identify which module is the PMM and the applicable power mode look up table.

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

1. 6: This step tests for battery voltage on the incorrect signal circuits.
2. 7: This step tests for no battery voltage on the required signal circuits.
3. 8: If any ignition switch parameters that should be inactive in the present ignition switch position are active, 2 ignition switch signal circuits may be shorted together.
4. 9: This step eliminates open circuits as the cause of the malfunction.

Power Mode Mismatch

This table is used for all retained accessory power (RAP) relay and RAP serial data controlled accessories which remain active after RAP has timed out. The RAP relay system can malfunction separately from the serial data controlled RAP system and the serial data controlled RAP system can malfunction separately from the RAP relay. If multiple accessories are not exhibiting an "On After Time-out" symptom, either on the RAP relay controlled circuit or the serial data controlled circuit or both, the malfunction is in a particular device and not in the RAP control system. Refer to Control Module References to locate information on a specific system.

Retained Accessory Power (RAP) On After Timeout

Retained Accessory Power (RAP) Inoperative

Retained Accessory Power (RAP) Inoperative

Control Module References

Control Module References

Data Link References

This table identifies which serial data link that a particular module uses for in-vehicle data transmission. Some modules may use more than one data link to communicate. Some modules may have multiple communication circuits passing through them without actively communicating on that data link. This table is used to assist in correcting a communication malfunction. For the description and operation of these serial data communication circuits refer to Data Link Communications Description and Operation .

Data Link References

Removal Procedure

1. Remove the left instrument panel (I/P) outer trim cover. Refer to «Instrument Panel (I/P) Outer Trim Cover Replacement»(/buick/lacrosse/i-2004-2009/remont/gauges-instrument-panels/#instrument-panel-gages-and-console) in Instrument Panel, Gages and Console.
2. Press to release the cam lock. Disconnect the upper electrical connector from the BCM.
3. Remove the left I/P insulator. Refer to «Closeout/Insulator Panel Replacement - Left»(/buick/lacrosse/i-2004-2009/remont/gauges-instrument-panels/#instrument-panel-gages-and-console) in Instrument Panel, Gages and Console.
4. Remove the knee bolster. Refer to «Knee Bolster Replacement - Left»(/buick/lacrosse/i-2004-2009/remont/gauges-instrument-panels/#instrument-panel-gages-and-console) in Instrument Panel, Gages and Console.
5. Press to release the cam lock. Disconnect the lower BCM electrical connectors.
6. Remove the BCM bracket screws and remove the BCM and bracket from the I/P.
7. Remove the BCM from the BCM bracket.

Installation Procedure

1. Install the BCM to the BCM bracket.
2. Install the BCM and BCM bracket to the I/P.
3. Install the BCM screws. Tighten: Tighten the screws to 2 N.m (18 lb in).
4. Connect the lower BCM electrical connectors. Engage the cam lock.
5. Install the knee bolster. Refer to «Knee Bolster Replacement - Left»(/buick/lacrosse/i-2004-2009/remont/gauges-instrument-panels/#instrument-panel-gages-and-console) in Instrument Panel, Gages and Console.
6. Install the left I/P insulator. Refer to «Closeout/Insulator Panel Replacement - Left»(/buick/lacrosse/i-2004-2009/remont/gauges-instrument-panels/#instrument-panel-gages-and-console) in Instrument Panel Gages and Console.
7. Connect the upper electrical connector to the BCM. Engage the cam lock.
8. Install the left I/P outer trim cover. Refer to «Instrument Panel (I/P) Outer Trim Cover Replacement»(/buick/lacrosse/i-2004-2009/remont/gauges-instrument-panels/#instrument-panel-gages-and-console) in Instrument Panel, Gages and Console.
9. Perform the new BCM setup. Refer to «Body Control Module (BCM) Programming/RPO Configuration»(/buick/lacrosse/i-2004-2009/remont/communication-devices/#computerintegrating-systems__body-control-module-bcm-programmingrpo-configuration) .

1. Disengage the data link connector (DLC) tab (1).
2. Remove the DLC from the instrument panel (I/P) trim pad.

1. Align the DLC to the I/P trim pad.
2. Slide the DLC upward in order to engage the tab (1).

Body Control Module (BCM) Programming/RPO Configuration

A new body control module (BCM) must be programmed with the proper RPO configurations. The BCM stores the information regarding the vehicle options and if the BCM is not properly configured with the correct RPO codes, the BCM will not control all of the features properly. The Tech 2 software will automatically prompt you with the possible RPO's available for the vehicle. Ensure that the following conditions exist and are met in order to prepare for BCM programming

Preparation

1. Understand this entire procedure.
2. The battery is fully charged.
3. The ignition switch is in the ON position.
4. The data link connector (DLC) is accessible.
5. All disconnected modules and devices are reconnected before programming.
6. Follow all Scan Tool on screen directions.
7. Take time to verify the VIN on the Scan Tool is correct, failure to do this could result in the service part being made unprogrammable.

BCM Setup

1. To setup a new BCM, navigate to the Module Setup menu in Computer Integrating Systems on the scan tool, select Body Control Module.
2. Run the BCM Setup, BPP Calibration and Program Key Fobs procedures.
3. If the BCM fails to accept the program, perform the following steps: Inspect all BCM connections. Verify that the scan tool has the latest software version.

Remote Start Programming

The Remote Start option can only be programmed with an SPS terminal and a Scan tool configured in the Pass Thru programming arrangement. Use this arrangement and select Remote Start setup on the SPS terminal once the programming options appear. Choose the appropriate settings when prompted for engaging or disengaging the Remote Start option. Refer to SERVICE PROGRAMMING SYSTEM (SPS) in Communications Devices proper procedure.

BPP Sensor Calibration

Perform the BPP Sensor Calibration using a scan tool if the BCM, EBCM or the brake apply sensing system (BASS) sensor has been replaced.

Using a scan tool preform the following

1. Navigate to the Module Setup menu in Computer Integrating Systems on the scan tool, select Body Control Module.
2. Select BPP Sensor Calibration.
3. Follow the on-screen directions.

Passkey 3 Programming Procedures

Perform the Passkey 3/VTD Programming Procedure if any of the following components have been replaced

1. The BCM
2. The powertrain control module (PCM)
3. Passkey sensor.

Refer to Programming Theft Deterrent System Components in Theft Deterrent for the programming procedure.

1. Turn the ignition OFF for 10 seconds.
2. Connect the scan tool to the data link connector.
3. Turn the ignition ON with the engine OFF.
4. Use the scan tool in order to retrieve history DTCs from all modules.
5. Clear all history DTCs.

There are 2 different communication networks on this vehicle: The class 2 network and the GMLAN network. The class 2 serial data circuit is the low speed link and the GMLAN serial data circuit is the high speed link. Modules that need real time communications are attached to the high speed network. The engine control module (ECM) is the gateway between the networks. The purpose of the gateway is to transfer information from one network to another.

GMLAN Circuit Description

The data link connector (DLC) allows a scan tool to communicate with the GMLAN serial data circuit. On this vehicle, only GMLAN high speed is used. That means that the serial data is transmitted on 2 wires at an average of 500 Kbps. The high speed dual wire GMLAN is a differential bus. That means that two bus lines, GMLAN high and GMLAN low are driven to opposite extremes from a rest or idle level. The idle level which is approximately 2.5 volts is considered a recessive transmitted data and is interpreted as a logic 1. Driving the lines to their extremes means adding 1 volt to GMLAN high wire and subtracting 1 volt from GMLAN low wire. This dominant state is interpreted as a logic 0. GMLAN network management supports selective start up and is based on virtual networks. A virtual network is a collection of signals started in response to a vehicle event. The starting of a virtual network signifies that a particular aspect of the vehicles functionality has been requested. A virtual network is supported by virtual devices which represents a collection of signals owned by a single physical device. So, any physical device can have one or more virtual devices. The signal supervision is the process of determining whether an expected signal is being received or not. Failsofting is the ability to substitute a signal with a default value or a default algorithm, in the absence of a valid signal. Some messages are also interpreted as a, heartbeat, of a virtual device. If such a signal is lost, the application will set a no communication code against the respective virtual device. This code is mapped on the Tech 2 screen as a code against the physical device. Note that a loss of serial data DTC does not normally represent a failure of the module that set it.

Class 2 Circuit Description

The data link connector (DLC) allows a scan tool to communicate with the class 2 serial data line. The serial data line is the means by which the microprocessor-controlled modules that are connected to it communicate with each other. Once the scan tool is connected to the class 2 serial data line through the DLC, the scan tool can be used to monitor each module for diagnostic purposes and to check for diagnostic trouble codes (DTCs). Class 2 serial data is transmitted on a single wire at an average of 10.4 Kbps. The bus is active at 7.0 volts nominal and inactive at ground potential. When the ignition switch is in RUN, each module communicating on the class 2 serial data line sends a state of health (SOH) message every 2 seconds to ensure that the module is operating properly. When a module stops communicating on the class 2 serial data line, for example if the module loses power or ground, the SOH message it normally sends on the data line every 2 seconds disappears. Other modules on the class 2 serial data line, which expect to receive that SOH message, detect its absence; those modules in turn set an internal DTC associated with the loss of SOH of the non-communicating module. The DTC is unique to the module which is not communicating, for example, when the body control module (BCM) SOH message disappears, several modules set DTC U1064. Note that a loss of serial data DTC does not normally represent a failure of the module that set it.

The data link connector (DLC) is a standardized 16 cavity connector. Connector design and location is dictated by an industry wide standard and is required to provide the following

1. Scan tool power battery positive voltage at terminal 16
2. Scan tool power ground at terminal 4
3. Common signal ground at terminal 5
4. Class 2 signal at terminal 2
5. GMLAN high circuit at terminal 6
6. GMLAN low circuit at terminal 14

GMLAN Serial Data Line

The GMLAN serial data communications circuit used on this vehicle is in a linear topology. The following modules are connected to the link, in order from DLC to the end of the linear configuration

The following modules communicate on the GMLAN serial data circuit

1. The transmission control module (TCM), (LY7) 3.6-L
2. The engine control module (ECM), (LY7) 3.6-L

Class 2 Serial Data Link

The class 2 serial data link allows the following modules to communicate and share data with each other

1. Body control module (BCM)
2. Digital radio receiver
3. Electronic brake control module (EBCM)
4. Engine Control Module (ECM) (LY7)
5. Instrument panel cluster (IPC)
6. HVAC module
7. Powertrain control module (PCM) (L26)
8. Radio
9. Inflatable restraint sensing and diagnostic module (SDM)
10. Vehicle control interface module (VCIM)

The class 2 serial data link allows a scan tool to communicate with the above modules for diagnostic and testing purposes.

Body Control System Description and Operation

The body control system consists of the body control module (BCM) and its associated controls. Battery positive voltage is provided to the BCM from the TURN/HAZ fuse and the CHMSL/BKUP fuse in the fuse block instrument panel (I/P). The module grounds are wired to ground G200, G201 and G301. The BCM is wired to the class 2 serial data communication bus as well as discrete input and output terminals to control the functions of the vehicles body.

Power Mode Master

This vehicles BCM functions as the Power Mode Master (PMM). Refer to Power Mode Description and Operation for a complete description of the power mode functions.

Body Control Module

The various body control module (BCM) input and output circuits are described in the corresponding functional areas indicated on the BCM electrical schematics. The BCM functions include the following

1. Battery rundown protection-Inadvertent power-Refer to «Interior Lighting Systems Description and Operation»(/buick/lacrosse/i-2004-2009/remont/exterior-lights/#lighting-systems) in Lighting Systems.
2. BTSI/automatic transmission shift lock control-Refer to «Automatic Transmission Shift Lock Control Description and Operation»(/buick/lacrosse/i-2004-2009/remont/automatic-trans/#shift-interlock-system__automatic-transmission-shift-lock-control-description) in Automatic Transaxle - 4T65-E.
3. Bulb check-Refer to «Instrument Panel Cluster (IPC) Description and Operation»(/buick/lacrosse/i-2004-2009/remont/gauges-instrument-panels/#instrument-panel-gages-and-console) in Instrument Panel, Gages and Console.
4. Chimes-Refer to «Audible Warnings Description and Operation»(/buick/lacrosse/i-2004-2009/remont/gauges-instrument-panels/#instrument-panel-gages-and-console__audible-warnings-description-and-operation) in Instrument Panel, Gages and Console. Check gages Content theft deterrent Door ajar warning Headlamps ON Key-in-ignition Oil reset Park brake warning Seat belt not fastened Turn signal ON Vehicle theft deterrent
5. Door lock interface-Refer to «Power Door Locks Description and Operation»(/buick/lacrosse/i-2004-2009/remont/door-locks-anti-theft-systems/#door-system-mirror-system-window-system) in Doors.
6. Exterior and interior lighting control-Refer to «Exterior Lighting Systems Description and Operation»(/buick/lacrosse/i-2004-2009/remont/exterior-lights/#lighting-systems) in Lighting Systems. Automatic lighting control Backup lamps Daytime running lights (DRL) Fog lamps High/low beam head lamps Park brake lights Turn hazard lamps
7. Gage control-Refer to «Instrument Panel Cluster (IPC) Description and Operation»(/buick/lacrosse/i-2004-2009/remont/gauges-instrument-panels/#instrument-panel-gages-and-console) in Instrument Panel, Gages and Console.
8. Heated seats-Refer to «Heated Seats Description and Operation»(/buick/lacrosse/i-2004-2009/remont/seats/#seat-system__heated-seats-description-and-operation) in Seats.
9. Horn interface-Refer to «Horns System Description and Operation»(/buick/lacrosse/i-2004-2009/remont/horns/#horn-system) in Horns.
10. Instrument cluster indicator control-Refer to «Instrument Panel Cluster (IPC) Description and Operation»(/buick/lacrosse/i-2004-2009/remont/gauges-instrument-panels/#instrument-panel-gages-and-console) in Instrument Panel, Gages and Console.
11. Interior lighting-Refer to «Interior Lighting Systems Description and Operation»(/buick/lacrosse/i-2004-2009/remont/exterior-lights/#lighting-systems) in Lighting Systems.
12. Key-in-ignition sensing-Refer to «Audible Warnings Description and Operation»(/buick/lacrosse/i-2004-2009/remont/gauges-instrument-panels/#instrument-panel-gages-and-console__audible-warnings-description-and-operation) in Instrument Panel, Gages and Console.
13. Parking brake state sensing-Refer to «Brake Warning System Description and Operation»(/buick/lacrosse/i-2004-2009/remont/mechanical-hydraulic/#hydraulic-brake-system) in Hydraulic Brakes.
14. Retained accessory power (RAP)-Refer to «Retained Accessory Power (RAP) Description and Operation»(/buick/lacrosse/i-2004-2009/remont/communication-devices/#computerintegrating-systems) in Retained Accessory Power.
15. Rear compartment interface-Refer to «Power Door Locks Description and Operation»(/buick/lacrosse/i-2004-2009/remont/door-locks-anti-theft-systems/#door-system-mirror-system-window-system) in Doors.
16. Rear defogger-Refer to «Rear Window Defogger Description and Operation»(/buick/lacrosse/i-2004-2009/remont/heated-glassdefoggers/#stationary-windows) in Stationary Windows.
17. Remote function control-Refer to «Keyless Entry System Description and Operation»(/buick/lacrosse/i-2004-2009/remont/door-locks-anti-theft-systems/#keyless-entry-system) in Keyless Entry.
18. RFA communication link-Refer to «Keyless Entry System Description and Operation»(/buick/lacrosse/i-2004-2009/remont/door-locks-anti-theft-systems/#keyless-entry-system) in Keyless Entry.
19. Seat belt use sensing-Refer to «Seat Belt System Description and Operation»(/buick/lacrosse/i-2004-2009/remont/restraints-control-systems/#seat-belt-system) in Seat Belts.
20. Theft deterrent vehicle/content-Refer to «Theft Systems Description and Operation»(/buick/lacrosse/i-2004-2009/remont/door-locks-anti-theft-systems/#theft-deterrent-system__theft-systems-description-and-operation) in Theft Deterrent.
21. Washer solvent level sensing-Refer to «Wiper/Washer System Description and Operation»(/buick/lacrosse/i-2004-2009/remont/wiperwasher-systems/#wiper-system-washer-system) in Wipers/Washer Systems.
22. Wiper/washer-Refer to «Wiper/Washer System Description and Operation»(/buick/lacrosse/i-2004-2009/remont/wiperwasher-systems/#wiper-system-washer-system) in Wipers/Washer Systems.

Power Mode Description and Operation

Power to many of this vehicle's circuits are controlled by the module that is designated the power mode master (PMM). This vehicle PMM is the body control module (BCM). The PMM controls which power mode (Run, Accessory, Crank, Retained Accessory Power or Off) is active.

Serial Data Power Mode

On vehicles that have several control modules connected by serial data circuits, one module is the power mode master (PMM). On this vehicle, the PMM is the body control module (BCM). The PMM receives 3 discrete ignition switch signals to differentiate which power mode will be sent over the Serial Data circuits. The table below illustrates the state of these inputs in correspondence to the ignition switch position

3-Wire Ignition Switch Table

Relay Controlled Power Mode

The body control module (BCM) uses the discrete ignition switch inputs ignition 1, ignition 3 and crank to distinguish the correct power mode. Once the BCM has determined the power mode selected by the vehicle operator it will energize the Ignition relay, Run relay and retained accessory power (RAP) relay, depending on which power mode is selected.

Ignition 1 Relay

The relay uses a Hot At All Times B+ power source derived from the underhood electrical center. The ignition 1 relay supplies a power signal to the following circuits when the Run or Crank power mode is selected

1. AC clutch relay
2. ABS STG angle sensor
3. Antilock brake system (ABS) yaw sensor
4. Auxiliary power drop connector
5. Crank relay
6. Cruse control switch
7. Electronic brake control module (EBCM)
8. Engine control module (ECM)
9. Heating, ventilation and air conditioning module (HVAC)
10. Ignition control module (ICM)
11. Instrument panel cluster (IPC)
12. Sensing and diagnostic module (SDM)
13. Transmission solenoid circuit

Retained Accessory Power (RAP) Relay

The RAP relay is energized when the Run or Accessory power mode has been selected. The relay uses a Hot At All Times B+ power source derived from the underhood electrical center. The B+ power source is protected by the 50 Amp BATT MAIN 2 fuse. The BCM also energizes the relay for 10 minutes after the vehicle operator transitions the ignition switch from Accessory to OFF or Run to OFF positions. The following circuits are controlled by the RAP relay

1. Power sunroof
2. Power windows

Fail-Safe Operation

Since the operation of the vehicle systems depends on the power mode, there is a fail-safe plan in place should the power mode master (PMM) fail to send a power mode message. The fail-safe plan covers those modules using exclusively serial data control of power mode as well as those modules with discrete ignition signal inputs.

Serial Data Messages

The modules that depend exclusively on serial data messages for power modes stay in the state dictated by the last valid PMM message until they can check for the engine run flag status on the serial data circuits. If the PMM fails, the modules monitor the serial data circuit for the engine run flag serial data. If the engine run flag serial data is True, indicating that the engine is running, the modules fail-safe to RUN. In this state the modules and their subsystems can support all operator requirements. If the engine run flag serial data is False, indicating that the engine is not running, the modules fail-safe to OFF-AWAKE. In this state the modules are constantly checking for a change status message on the serial data circuits and can respond to both local inputs and serial data inputs from other modules on the vehicle.

Discrete Ignition Signals

Those modules that have discrete ignition signal inputs also remain in the state dictated by the last valid PMM message received on the serial data circuits. They then check the state of their discrete ignition input to determine the current valid state. If the discrete ignition input is active, battery positive voltage, the modules will fail-safe to the RUN power mode. If the discrete ignition input is not active, open or 0 volts, the modules will fail-safe to OFF-AWAKE. In this state the modules are constantly checking for a change status message on the serial data circuits and can respond to both local inputs and serial data inputs from other modules on the vehicle.

BCM Wake-Up/Sleep States

The body control module (BCM) is able to control or perform all of the BCM functions in the wake-up state. The BCM enters the sleep state when active control or monitoring of system functions has stopped and the BCM has become idle again. The BCM must detect certain wake-up inputs before entering the wake-up state. The BCM monitors for these inputs during the sleep state, where the BCM is able to detect switch transitions that cause the BCM to wake-up when activated or deactivated. Multiple switch inputs are needed in order to sense both the insertion of the ignition key and the power mode requested. This would allow the BCM to enter a sleep state when the key is IN or OUT of the ignition.

The BCM will enter a wake-up state if any of the following wake-up inputs are detected

1. Activity on the serial data line
2. Detection of a battery disconnect and reconnect condition
3. Headlamps are ON.
4. Ignition is turned ON.
5. Key-in-ignition switch
6. Park lamps are ON.

The BCM will enter a sleep state when all of the following conditions exist

1. The ignition switch is OFF.
2. No activity exists on the serial data line.
3. No outputs are commanded.
4. No delay timers are actively counting.
5. No wake-up inputs are present.

If all these conditions are met the BCM will enter a low power or sleep condition. This condition indicates that the BCM, which is the power mode master (PMM) of the vehicle, has sent an OFF-ASLEEP message to the other systems on the serial data line.

Serial Data Control of Retained Accessory Power (RAP)

Retained accessory power (RAP) is a vehicle power mode that permits the operation of selected customer convenience items after the ignition switch is turned OFF. These selected items will remain in operation until a passenger compartment door is opened or until the RAP function timer reaches its time-out limit.

The modules listed below all receive a RAP message from the body control module (BCM) over the serial data circuits. The BCM monitors the ignition switch position, battery condition and passenger compartment door status to determine whether RAP should be initiated. The BCM then sends a message to the listed modules telling them that they are in RAP power mode. The modules then support the operation of the systems under their control as required by their RAP power mode strategy.

RAP will end when one of the following conditions are met

1. The BCM receives an input (as a hard wired input from the door switches) indicating the opening of a passenger compartment door.
2. The BCM receives a message from its internal timer indicating the end of the RAP period after 10 minutes.
3. The BCM detects a decrease in battery capacity below a prescribed limit.
4. The transition from OFF to RUN/ON or ACC of the ignition switch.

The BCM then sends a serial data message to the listed devices ending the RAP function.

The devices receiving serial data messages for RAP functions are

1. Driver information center (DIC)
2. Digital radio receiver (DRR), if equipped
3. Head up display (HUD)
4. Instrument panel cluster (IPC)
5. Radio
6. Vehicle communication interface module (VCIM), if equipped

Relay Control of Retained Accessory Power (RAP)

Retained accessory power (RAP) is a vehicle power mode that permits the operation of selected customer convenience items after the ignition switch is turned OFF. These selected items will remain in operation until a passenger compartment door is opened or until the RAP function timer reaches its time-out limit.

The body control module (BCM) activates the RAP relay in either the RAP function as described above or if the BCM detects a RUN/ON or accessory power mode. This provides power for the following

1. The power windows
2. The sunroof control module, if equipped

The BCM deactivates the RAP relay to end the RAP function when it ends the RAP function as outlined in the previous text.

See also:
• SIR DISABLING AND ENABLING ZONES
• Diagnostic System Check - Vehicle
• Master Electrical Component List
• Testing for Intermittent Conditions and Poor Connections
• Circuit Testing
• Wiring Repairs
• Ignition Switch Replacement
• Connector Repairs
• Engine Controls Schematics
• Powertrain Control Module (PCM) Connector End Views
• Engine Controls Connector End Views
• Diagnostic Trouble Code (DTC) List - Vehicle
• Checking Aftermarket Accessories
• Symptoms - Lighting Systems
• Radio/Audio System Schematics
• HVAC Schematics
• Blower Control Module Replacement
• Body Control Module Programming and Setup
• OnStar Schematics
• OnStar Reconfiguration
• Digital Radio Receiver Setup
• ABS Schematics
• Driver Information System Schematics
• Engine Controls Schematics
• Engine Control Module Programming and Setup (3.6L - LY7)
• Garage Door Opener Schematics
• Garage Door Opener Replacement
• HVAC Schematics
• HVAC Control Module Programming and Setup
• SIR Schematics
• Passenger Presence System Programming and Setup
• Inflatable Restraint Sensing and Diagnostic Module Programming and Setup
• Object Detection Schematics
• Powertrain Control Module (PCM) Replacement
• Powertrain Control Module Programming and Setup
• Radio Setup
• Keyless Entry Schematics
• Transmitter Programming
• Power Sunroof Schematics
• Sunroof Control Module Programming and Setup (One Connector System)
• Automatic Transmission Controls Schematics
• Transmission Control Module (TCM) Replacement (3.8L)
• Transmission Control Module Programming and Setup
• Fastener Notice
• SERVICE PROGRAMMING SYSTEM (SPS)
• Programming Theft Deterrent System Components
• Automatic Transmission Shift Lock Control Description and Operation
• Audible Warnings Description and Operation
• Power Door Locks Description and Operation
• Heated Seats Description and Operation
• Horns System Description and Operation
• Brake Warning System Description and Operation
• Rear Window Defogger Description and Operation
• Seat Belt System Description and Operation
• Theft Systems Description and Operation
• Wiper/Washer System Description and Operation
• DTC B1000
• Control Module References
• Scan Tool Does Not Communicate with High Speed GMLAN Device
• Data Link References
• Body Control System Description and Operation
• Body Control Module (BCM) Programming/RPO Configuration
• Power Mode Description and Operation