Computer/integrating Systems Cadillac SRX I

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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Dash Integration Module (DIM) C1

Dash Integration Module (DIM) C1 Connector Part Information 12064871 10-Way F Metri-Pack 150 Series (BU) Pin Wire Color Circuit No. Function A-D - - Not Used E BK/WH 351 Ground F - - Not Used G RD/WH 1140 Battery Positive Voltage H YE 32 Instrument Panel Lamp Fuse Supply Voltage J - - Not Used K YE 1491 Backlight Lamps Control

Dash Integration Module (DIM) C2

Dash Integration Module (DIM) C2 Connector Part Information 12160778 24-Way F Micro-Pack 100 Series (BN) Pin Wire Color Circuit No. Function A1-A3 - - Not Used A4 D-GN 44 Instrument Panel Lamps Dimmer Switch Signal A5 - - Not Used A6 YE 5005 Instrument Panel Lamps Dimmer Switch Low Reference A7 L-BU/BK 1688 5-Volt Reference A8 TN/WH 99 Windshield Washer Fluid Level Signal A9 L-BU 1717 Hazard Switch Output A10 - - Not Used A11 PU 1807 Class 2 Serial Data A12 PU 1807 Class 2 Serial Data B1 PK/BK 109 Hood Ajar Switch Signal (UA2) B2 WH 103 Headlamp Switch Headlamps On Signal B3 BN/WH 301 Rear Park Lamps Supply Voltage B4 WH 1538 Windshield Wiper Switch On Signal B5 PU 1783 Twilight Sentinel Delay Signal B6 OG 192 Front Fog Lamp Switch Signal B7 L-BU 187 Rear Fog Lamp Switch Signal (T79) B8 BN 1356 Flash-To-Pass Switch Signal B9 PK/BK 1597 Courtesy Lamps Switch On Signal B10 L-GN 80 Key In Ignition Switch Signal B11-B12 - - Not Used

Dash Integration Module (DIM) C3

Dash Integration Module (DIM) C3 Connector Part Information 12110088 24-Way F Micro-Pack 100 Series (GY) Pin Wire Color Circuit No. Function A1 - - Not Used A2 BN 4 Accessory Voltage A3 PK 3 Ignition 1 Voltage A4 L-GN/BK 592 DRL Relay Control (w/o T62) A5 WH 111 Hazard Switch Signal A6 TN 28 Horn Relay Control A7 D-GN/WH 1317 Fog Lamp Relay Control A8 D-GN 1399 RAP Relay Coil Supply Voltage A9-A11 - - Not Used A12 RD/WH 3340 Battery Positive Voltage B1-B3 - - Not Used B4 PK/WH 1970 Headlamp Low Beam Relay Control B5 WH 1080 Park Lamp Relay Control B6 TN 5052 Headlamp Washer Ground (CE4) B7 TN/WH 1969 Headlamp High Beam Relay Control B8 D-GN 1483 Control Power - Output B9 TN 5026 Ignition Lock Cylinder Control Switch Signal B10-B11 - - Not Used B12 BK/WH 51 Ground

Data Link Connector (DLC)

Data Link Connector (DLC) Connector Part Information 12110250 16-Way F Metri-Pack 150 Series (BK) Pin Wire Color Circuit No. Function 1 - - Not Used 2 PU 1807 Class 2 Serial Data (Primary) 3 - - Not Used 4 BK 350 Ground 5 BK/WH 351 Ground 6 TN/BK 2500 High Speed GMLAN Serial Data Bus+ 7 WH/BK 5043 Keyword 2000 Serial Data (TR7) 8-13 - - Not Used 14 TN 2501 High Speed GMLAN Serial Data Bus- 15 - - Not Used 16 RD/WH 1140 Battery Positive Voltage

Rear Integration Module (RIM) C1

Rear Integration Module (RIM) C1 Connector Part Information 12092632 16-Way F Micro-Pack 100 Series (RD) Pin Wire Color Circuit No. Function A1 L-BU 5362 Inclination Sensor Signal (UA2) A2 BN/WH 1571 Traction Control Switch Signal A3 D-BU 2181 Passenger Heated Seat Control Module Status Signal (KA1) A4 PK 1339 Ignition 1 Voltage A5 D-BU/WH 149 Courtesy Lamp Control A6 TN/BK 5168 Theft Deterrent Alarm Enable Signal (UA2) A7 L-BU/WH 181 Heated Seat Control Module Status Signal (KA1) A8 BK/WH 1051 Ground B1-B2 - - Not Used B3 OG/BK 744 Rear Compartment Lid Ajar Switch B4 - - Not Used B5 L-BU 9534 Rear Parking Aid Chime B6-B7 - - Not Used B8 BK/WH 1051 Ground

Rear Integration Module (RIM) C2

Rear Integration Module (RIM) C2 Connector Part Information 12160778 24-Way F Micro-Pack 100 Series (BN) Pin Wire Color Circuit No. Function A1 TN 755 RAP Relay Coil Control (C3B/CF5 w/o T79) A2 - - Not Used A3 YE 1977 Rear Fog Lamp Relay Control (T79) A4 - - Not Used A5 D-GN/WH 1135 A/T Shift Lock Control Solenoid Supply Voltage A6 BN/WH 1429 Standing Lamp Relay Control (T79) A7 - - Not Used A8 PK 5363 Inclination Sensor Low Reference (UA2) A9 - - Not Used A10 GY 157 Courtesy Lamp Control A11 RD/WH 540 Courtesy Lamp Control A12 PU 1807 Class 2 Serial Data B1 WH 193 Rear Defog Relay Control B2 D-GN 646 Reverse Relay Control B3-B4 - - Not Used B5 D-BU 1393 Courtesy Lamps Supply Voltage B6 YE 5058 Intrusion Sensor Armed Signal (UA2) B7 PK/BK 1503 Passenger Heated Seat High/Low Signal (KA1) B8 PK 1501 Driver Heated Seat High/Low Signal (KA1) B9 - - Not Used B10 GY 157 Courtesy Lamp Control B11 BK 1050 Ground B12 PU 1807 Class 2 Serial Data

Diagnostic Code Index

DIAGNOSTIC CODE INDEX

Begin the system diagnosis with Diagnostic System Check - Vehicle . 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

Rear Integration Module (RIM)

Scan Tool Data List

Dash Integration Module (DIM)

Rear Integration Module (RIM)

Door Modules

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 module 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

The module has detected an internal malfunction.

Action Taken When the DTC Sets

The module 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

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

This diagnostic procedure supports the following DTC

DTC B1004 Keep Alive Memory (KAM) Reset

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 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 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) check sum 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 check sum test. The blocks of data that have not failed the check sum 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

Normal vehicle class 2 communication will not commence until the system power mode has been identified. The dash integration module (DIM) is the power mode master (PMM). The DIM communicates the system power mode to all the modules connected to the class 2 serial data circuit. The DIM monitors the state of the IGN 1 and Accessory voltage circuits in order to determine the present system power mode.

This diagnostic procedure supports the following DTC

DTC B1372 Device Ignition 1 Circuit Low

Anytime the DIM receives an input or message.

The DIM has detected the IGN 1 voltage circuit is low for greater than 1 minute when the Accessory voltage circuit is high and the engine run flag is true.

1. DTC B1372 is set in the DIM.
2. The malfunction indicator lamp (MIL) is illuminated.
3. The DIM along with other modules on the class 2 serial data circuit, will execute the power mode backup strategy.

Conditions for Clearing the MIL/DTC

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

Refer to Testing for Intermittent Conditions and Poor Connections .

Device Power Moding

Test Description

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

1. 6: This step tests for a short to battery voltage on the active signal circuit.
2. 7: This step tests the inactive signal circuit for an open or a high resistance.
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.

DTC B1372

Normal vehicle class 2 communication will not commence until the system power mode has been identified. The dash integration module (DIM) is the power mode master (PMM). The DIM communicates the system power mode to all the modules connected to the class 2 serial data circuit. The DIM monitors the state of the IGN 1 and Accessory voltage circuits in order to determine the present system power mode.

This diagnostic procedure supports the following DTC

DTC B1382 Device Ignition Accessory Circuit Low

Anytime the DIM receives an input or message.

The DIM has detected the Accessory voltage circuit is low for greater than 1 minute when the IGN 1 voltage circuit is high and the engine run flag is true.

1. DTC B1382 is set in the DIM.
2. The malfunction indicator lamp (MIL) is illuminated.
3. The DIM along with other modules on the class 2 serial data circuit, will execute the power mode backup strategy.

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

Refer to Testing for Intermittent Conditions and Poor Connections .

Device Power Moding

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

1. 6: This step tests for a short to battery voltage on the active signal circuit.
2. 7: This step tests the inactive signal circuit for an open or a high resistance.
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.

DTC B1382

The dash integration module (DIM) has an internal battery voltage sense input and a reference voltage input. The DIM 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 DIM has battery positive voltage 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 1 volt or greater.

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

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 DTC Symptom Description .

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»(/cadillac/srx/i-2003-2009/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»(/cadillac/srx/i-2003-2009/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.

This diagnostic procedure supports the following DTC

DTC U0002 Fewer Controllers On than Programmed

This vehicle has DTCs which include DTC Symptoms. For more information on DTC Symptoms, refer to DTC Symptom Description .

DTC U0002

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

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 U0002

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)

This vehicle has DTCs which include DTC Symptoms. For more information on DTC Symptoms, refer to DTC Symptom Description .

DTC U0100-U0299

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 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 5 seconds of beginning serial data communication, DTC U1000 is set. When more than one critical parameter does not have an identification number associated with it, the DTC will only be reported once.

The class 2 serial data line on this vehicle is a star configuration, with the body control module (BCM) and powertrain control module (PCM) each have a second class 2 serial data line between them. The following modules communicate on the class 2 serial data line

1. The audio amplifier (AMP)
2. The CD changer (CDX)
3. The dash integration module (DIM)
4. The driver door module (DDM)
5. The driver door switch assembly (DDSA)
6. The digital radio receiver (DRR)
7. The digital video disc (DVD) player
8. The electronic brake control module (EBCM)
9. The electronic suspension control (ESC) module
10. The front passenger door module (FPDM)
11. The HVAC control module
12. The inflatable restraint sensing and diagnostic module (SDM)
13. The instrument panel cluster (IPC)
14. The left rear door module (LRDM)
15. The memory seat module (MSM)
16. The powertrain/engine control module (PCM/ECM)
17. The radio
18. The radio antenna module (ARS)
19. The rear integration module (RIM)
20. The rear seat module (RSM)
21. The right rear door module (RRDM)
22. The theft deterrent control module (VTD)
23. The TV antenna module
24. The vehicle communication interface module (VCIM)

This diagnostic procedure supports the following DTC

DTC U1000 Class 2 Data Link Malfunction

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

A node alive message has not been received from an unidentified module within the last 5 seconds after establishing class 2 serial data communication.

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.

When a malfunction occurs while modules are communicating, a lost communication DTC 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 U1000 is set current by the other modules. If the malfunction occurs when the modules are not communicating, only U1000 is set.

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

1. 2: A DTC U1001 - U1254 Lost Communications with XXX with a history status may indicate the cause of U1000.
2. 3: The modules not communicating are the likely cause of U1000. The modules that are available on the class 2 serial data circuit are listed in the Circuit Description.
3. 7: The module which was not communicating due to a poor connection to the class 2 serial data circuit may have set DTC U1001 - U1254 Lost Communications with XXX for those modules that it was monitoring.
4. 10: The modules which can communicate indicate the module which cannot communicate. You must clear the serial data communication DTCs from these modules to avoid future misdiagnosis.
5. 13: If all modules are communicating, the module which set U1000 may have done so due to some other condition.
6. 15: The module which set U1000 is the likely cause of the malfunction.

DTC U1000

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. 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 module's 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 below provides a method for determining which module is not communicating. A module with a class 2 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 can not communicate.

DTC U1001-U1254

When more than one Loss of Communication DTC is set in either 1 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.
3. From the lowest number DTC to the highest number DTC.

1. The following diagnostic trouble codes do not have a current status: B1327 B1328 U1300 U1301 U1305
2. The vehicle power mode requires serial data communication to occur.

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

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.

When multiple Loss of Communication DTCs are set concurrently, the cause is likely to be 2 opens in the ring portion of the class 2 serial data circuit. Use the Control Module ID Number list in order to determine which modules are not communicating. Use the class 2 serial data circuit schematic in order to determine the location of the opens.

1. An intermittent open between the inoperative module and a star connector may cause this code to set.
2. A poor connection at the inoperative module or a star connector may cause this code to set.
3. An intermittent open in a star connector may cause this code to set.
4. An improperly powered module may cause this code to set.

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

1. 7: The module which was not communicating on the class 2 serial data circuit may have set Loss of Communication DTCs for those modules that it was monitoring.

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.

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

This vehicle has DTCs which include DTC Symptoms. For more information on DTC Symptoms, refer to DTC Symptom Description .

DTC U1300, U1301 or U1305

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.

These DTCs can be retrieved with a current status from engine control module (ECM) only, because ECM communicates functionally on both class 2 and high speed GMLAN serial data circuits, but ECM communication with the scan tool is via high speed GMLAN.

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

1. 4: This step takes out from the class 2 bus the modules connected to splice pack SP304.
2. 5: This step takes out from the class 2 bus the modules connected to splice pack SP300.
3. 6: This step takes out from the class 2 bus the modules connected to splice pack SP200.
4. 7: This test localizes the short on the rest of modules/circuits still connected to class 2 circuits of the ECM.
5. 14: If there are no current DTCs that begin with a U, the communication malfunction has been repaired.
6. 15: The communication malfunction may have prevented diagnosis of the customer complaint.

DTC U1300, U1301, or U1305

1. Perform the «Diagnostic System Check - Vehicle»(/cadillac/srx/i-2003-2009/remont/oem-general-information/#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»(/cadillac/srx/i-2003-2009/remont/communication-devices/#computerintegrating-systems) «Body Control System Description and Operation»(/cadillac/srx/i-2003-2009/remont/communication-devices/#computerintegrating-systems__body-control-system-description-and-operation) «Retained Accessory Power (RAP) Description and Operation»(/cadillac/srx/i-2003-2009/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»(/cadillac/srx/i-2003-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing__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 Conditions and Poor Connections .

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»(/cadillac/srx/i-2003-2009/remont/communication-devices/#computerintegrating-systems)
2. «Scan Tool Does Not Communicate with Class 2 Device»(/cadillac/srx/i-2003-2009/remont/communication-devices/#computerintegrating-systems)
3. «Scan Tool Does Not Communicate with High Speed GMLAN Device»(/cadillac/srx/i-2003-2009/remont/communication-devices/#computerintegrating-systems__scan-tool-does-not-communicate-with)
4. «Scan Tool Does Not Communicate with Keyword Data Line»(/cadillac/srx/i-2003-2009/remont/communication-devices/#computerintegrating-systems)
5. «Power Mode Mismatch»(/cadillac/srx/i-2003-2009/remont/communication-devices/#computerintegrating-systems)
6. «Retained Accessory Power (RAP) On After Timeout»(/cadillac/srx/i-2003-2009/remont/communication-devices/#computerintegrating-systems__retained-accessory-power-rap-on-after)
7. «Retained Accessory Power (RAP) Inoperative»(/cadillac/srx/i-2003-2009/remont/communication-devices/#computerintegrating-systems__retained-accessory-power-rap-inoperative)

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.

The engine will not start when there is a total loss of class 2 serial data communication while the ignition is OFF. The following conditions will cause a total loss of class 2 serial data communication

1. A class 2 serial data circuit shorted to ground
2. A class 2 serial data circuit shorted to voltage
3. An internal condition within a module or connector on the class 2 serial data circuit, that causes a short to voltage or ground to the class 2 serial data circuit

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

1. 2: A partial malfunction in the class 2 serial data circuit uses a different procedure from a total malfunction of the class 2 serial data circuit. The following modules communicate on class 2 serial data bus: The audio amplifier (AMP) The CD changer (CDX) The dash integration module (DIM) The digital radio receiver (DRR) The digital video disc (DVD) player The driver door module (DDM) The driver door switch assembly (DDSA) The electronic brake control module (EBCM) The electronic suspension control (ESC) module The engine control module (ECM) communicates functionally on class 2 and high speed GMLAN, but with scan tool it communicates via high speed GMLAN only The front passenger door module (FPDM) The HVAC control module The inflatable restraint sensing and diagnostic module (SDM) The instrument panel cluster (IPC) The left rear door module (LRDM) The memory seat module (MSM) w/A45 The radio The radio antenna module The rear integration module (RIM) The rear seat module (RSM) The right rear door module (RRDM) The theft deterrent control module The TV antenna module The vehicle communication interface module (VCIM)
2. 3: The following DTCs may be retrieved with a history status, but 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 code having a current status. This indicates that the malfunction occurred when the ignition was ON.
4. 7: Data link connector terminals 2 and 5 provide the connection to the class 2 serial data circuit and the signal ground circuit respectively.
5. 10: This step takes out from the class 2 bus the modules connected to splice pack SP304, excepting SDM and RIM.
6. 11: This step takes out from the class 2 bus the modules connected to splice pack SP300, excepting IPC.
7. 13: This test isolates the class 2 serial data circuit between DLC and DIM.
8. 18: This test localizes the class 2 serial data circuit of the suspected bus that is shorted.
9. 22: If there are no current DTCs that begin with a U, the communication malfunction has been repaired.
10. 23: The communication malfunction 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 high speed GMLAN serial data circuits monitor for serial data communications on the high speed 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 U0001 will be set. This DTCs can be retrieved as history only.

The high speed GMLAN serial data bus uses two 120 ohms terminating resistors that are in parallel with the high speed GMLAN (+) and (-) circuits. One of the resistors is connected at the transmission control module (TCM) and the other is at the engine control module (ECM). When testing for a short between high speed GMLAN (+) and (-) a reading of 60 ohms is normal. If the high speed GMLAN serial data is open testing the resistance between high speed GMLAN (+) and (-) will read about 120 ohms.

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

1. A short between high speed GMLAN (+) and high speed GMLAN (-) circuits
2. Any of the high speed GMLAN serial data circuits shorted to ground or voltage
3. A module internal malfunction that causes a short to voltage or ground on the high speed GMLAN circuits
4. Any of the high speed GMLAN serial data circuits open

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

1. 2: A partial malfunction in the high speed GMLAN serial data circuits uses a different procedure from a total malfunction of the high speed GMLAN data circuits. The following modules communicate on the high speed GMLAN serial data circuits: The ECM The TCM
2. 7: Data link connector terminals 6 and 14 provide the connection to the GMLAN serial data high circuit and the GMLAN serial data low circuit respectively.
3. 14: The communication malfunction may have prevented diagnosis of the customer complaint.

Scan Tool Does Not Communicate with High Speed GMLAN Device

The Keyword protocol utilizes a single wire bi-directional data line between the modules and the scan tool. The message structure is a request and response arrangement. Keyword serial data is used for scan tool diagnostics only. The modules do not exchange data on this circuit.

The following modules are connected to the Keyword serial data circuit

1. Headlamp - Left w/export
2. Headlamp - Right w/export

Scan Tool Does Not Communicate with Keyword Data Line

Normal vehicle class 2 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 the power mode master (PMM) module in order to determine the correct power mode. The PMM communicates the system power mode to all class 2 modules on the class 2 serial data line. 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 step numbers on the diagnostic table.

1. 6: This step tests for battery voltage on the signal circuits that are not required.
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

Retained Accessory Power (RAP) On After Timeout

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. This table is used to assist in correcting a communication malfunction between the control module and the scan tool. 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 instrument panel (I/P) compartment. Refer to «Compartment Replacement - Instrument Panel (I/P)»(/cadillac/srx/i-2003-2009/remont/gauges-instrument-panels/#instrument-panel-gages-and-console) in Instrument Panel, Gages, and Console.
2. Release the tabs securing the dash integration module (DIM) to the bracket.
3. Disconnect the electrical connectors.
4. Remove the module.

Installation Procedure

1. Connect the electrical connectors to the DIM.
2. Locate the DIM to the bracket on the I/P.
3. Push the DIM in order to lock the bracket retainers.
4. Install the I/P compartment. Refer to «Compartment Replacement - Instrument Panel (I/P)»(/cadillac/srx/i-2003-2009/remont/gauges-instrument-panels/#instrument-panel-gages-and-console) in Instrument Panel, Gages, and Console.
5. Reprogram the DIM. Refer to «Control Module References»(/cadillac/srx/i-2003-2009/remont/communication-devices/#computerintegrating-systems__control-module-references) .

1. Remove the right rear body side trim. Refer to «Trim Panel Replacement - Body Side Rear (w/o TB5)»(/cadillac/srx/i-2003-2009/remont/exteriorinterior-trim/#interior-trim) or «Trim Panel Replacement - Body Side Rear (w/TB5)»(/cadillac/srx/i-2003-2009/remont/exteriorinterior-trim/#interior-trim) .
2. Disconnect the electrical connectors (1) from the rear body control module.
3. Remove the module from the mounting bracket.

1. Install the module to the mounting bracket.
2. Connect the electrical connectors (1).
3. Install the right rear body side trim. Refer to «Trim Panel Replacement - Body Side Rear (w/o TB5)»(/cadillac/srx/i-2003-2009/remont/exteriorinterior-trim/#interior-trim) or «Trim Panel Replacement - Body Side Rear (w/TB5)»(/cadillac/srx/i-2003-2009/remont/exteriorinterior-trim/#interior-trim) .
4. Reprogram the module. Refer to «Control Module References»(/cadillac/srx/i-2003-2009/remont/communication-devices/#computerintegrating-systems__control-module-references) .

General Information to Set Up a Dash Integration Module (DIM)

Before performing any of the set up procedures ensure the following

1. Ensure the scan tool has been updated with the latest software version.
2. Ensure the battery is fully charged.
3. Ensure all modules on the serial data line are connected.

To set up a new DIM, the following procedures have to be performed

1. Program the VIN
2. Learning the restraints ID
3. Setting options

Program the VIN

Select "New VIN" under the DIM special functions menu, and follow the Tech 2 on-screen instructions.

Learning the Restraints ID

Select "Setup SDM Serial Number in DIM" under the DIM special functions menu, and follow the Tech 2 on-screen instructions.

Setting Options

Select "Set Options" under the DIM special functions menu, and follow the Tech 2 on-screen instructions. The following options can be set up

1. Point of Sale
2. Miscellaneous Options 2
3. Variable Effort Steering
4. Personalization Option
5. Universal Theft Deterrent
6. Headlamp Type Option
7. Intrusion Sensor Part A
8. Intrusion Sensor Part B
9. Inclination Sensor Part A
10. Inclination Sensor Part B
11. Alarm Siren Module Part A
12. Alarm Siren Module Part B
13. Twilight Sentinel
14. Front Fog Lamp Type
15. Daytime Running Lamp (DRL) Option
16. Perimeter Lighting
17. Tire Pressure Monitor (TPM) Option Enable
18. Electronic Suspension Control

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.

General Information to Set Up a Rear Integration Module (RIM)

Before setting up any option ensure the following

1. Ensure the scan tool has been updated with the latest software version.
2. Ensure the battery is fully charged.
3. Ensure all modules on the serial data line are connected.

Select "Set Options" under the dash integration module (DIM) special functions menu, and follow the Tech 2 on-screen instructions. The following options need to be set, when the rear integration module (RIM) is replaced. All listed options are for export only, and the selection should be No for domestic vehicles.

1. Intrusion Sensor Part A
2. Intrusion Sensor Part B
3. Inclination Sensor Part A
4. Inclination Sensor Part B
5. Alarm Siren Module Part A
6. Alarm Siren Module Part B

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.

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 serial data at terminal 2
5. Keyword serial data at terminal 7
6. High Speed GMLAN (+) serial data at terminal 6
7. High Speed GMLAN (-) serial data at terminal 14

The serial data circuits are the means by which the control modules on the vehicle communicate with each other and the scan tool. There are 3 different types of protocols on this vehicle.

1. The class 2 serial data
2. The keyword 2000 serial data
3. The high speed GMLAN serial data

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. Refer to Body Control System Description and Operation for operation of the PMM.

Class 2 Serial Data

The data link connector (DLC) allows a scan tool to communicate with the class 2 serial data line. This serial data line is the means by which the microprocessor-controlled modules in the vehicle 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 DTCs. Class 2 serial data is transmitted on a single wire at an average of 10.4 kbps. This value is an average, class 2 uses a variable pulse width modulation to carry data and depending on the message it may operate faster or slower. The bus will float at a nominal 7 volts during normal operation. Each module can pull this lower during the transmission. The bus is not at battery positive voltage or ground potential during normal operation. 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 inflatable restraint sensing and diagnostic module (SDM) SOH message disappears, several modules set DTC U1088. Note that a loss of serial data DTC does not normally represent a failure of the module that set it.

Class 2 Serial Data Circuit

The class 2 serial data circuit on this vehicle consists of a hybrid ring and star configuration. Each module on the ring has 2 class 2 serial data circuits connected to it. If there is one open on the ring, serial data communication will still take place. If there is more than one open on the ring, the modules not connected to the class 2 serial data circuit will not communicate. If there is one open on the star, the module not connected to the class 2 serial data circuit will not communicate. The following modules and splice packs are connected to the class 2 serial data circuit in a ring fashion

1. SP200
2. The instrument panel cluster (IPC)
3. SP300
4. The inflatable restraint sensing and diagnostic module (SDM)
5. SP304
6. The rear integration module (RIM)
7. The dash integration module (DIM)
8. The radio
9. The CD changer (CDX)
10. The HVAC control module
11. The engine control module (ECM)
12. The electronic brake control module (EBCM)

The star has the following 3 splice packs

1. SP200 located in the left side of the instrument panel, near the steering column, taped to the instrument panel harness
2. SP304 located in the right rear of the passenger compartment, taped to the body harness, approximately 24 cm (9.5 in) from the fuse block - right rear
3. SP300 located in the left side middle of the passenger compartment, taped to the body harness, near the carpet seam

The following devices are connected to the class 2 serial data circuit in star fashion via splice packs

1. SP200 The data link connector (DLC) The theft deterrent control module (VTD) The digital video disc (DVD) player
2. SP304 The right rear door module (RRDM) The rear seat module (RSM) The radio antenna module The TV antenna module The vehicle communication interface module (VCIM) The digital radio receiver (DRR) The front passenger door module (FPDM) The electronic suspension control (ESC) module
3. SP300 The audio amplifier (AMP) The left rear door module (LRDM) The driver door switch assembly (DDSA) The driver door module (DDM) The memory seat module (MSM) w/A45

Refer to Data Link Connector (DLC) Schematics in order to familiarize yourself with the architecture of the class 2 serial data circuit.

GMLAN Circuit Description

The data link connector (DLC) allows a scan tool to communicate with the high speed GMLAN serial data circuit. The serial data is transmitted on 2 twisted wires that allow speed up to 500 Kbps. The twisted pair is terminated with two 120 ohm resistors, one is internal to the engine control module (ECM) and the other is internal to the transmission control module (TCM). The resistors are used to reduce noise on the high speed GMLAN bus during normal vehicle operation. The high speed GMLAN is a differential bus. The high speed GMLAN serial data bus (+) and high speed GMLAN serial data (-) 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 adds 1 volt to high speed GMLAN serial data bus (+) and subtracts 1 volt from high speed GMLAN serial data bus (-) wire. This dominant state is interpreted as a logic 0.

The modules on the GMLAN serial data line are

1. The ECM
2. The TCM

Keyword Serial Data Line (TR7)

The keyword protocols utilize a single wire bi-directional data line between the modules and the scan tool. The message structure is a request and response arrangement. The keyword serial data line is used for scan tool diagnostics only. The modules do not exchange data on this circuit.

The modules on the GMLAN serial data line are

1. Headlamp - Left
2. Headlamp - Right

Body Control System Description and Operation

The body control system consists of the following 2 modules

1. The dash integration module (DIM)
2. The rear integration module (RIM)

Each of the 2 body control modules integrate a number of functional systems. Each module is connected to the class 2 serial data circuit, many of the control signals are implemented by class 2 messages.

Dash Integration Module (DIM)

The various dash integration module (DIM) input and output circuits are described in the corresponding functional areas as indicated on the DIM electrical schematics.

The DIM functions include the following

1. Cigar lighter relay control
2. Class 2 communication requiring DIM interaction
3. Exterior lighting control
4. Headlamp washer control
5. Hood ajar switch input w/export
6. Horn relay control
7. Interior lighting control
8. Load management
9. Low side temperature for HVAC compressor
10. Park key lock output
11. Power moding control over class 2 serial data circuit
12. Reverse lockout solenoid control
13. Steering wheel controls input
14. Storage of the clock settings and sending a message out on the class 2 serial data circuit in response to requests from other modules
15. Storage of vehicle options and configuration

Power Mode

The dash integration module (DIM) is the power mode master (PMM). Refer to Power Mode Description and Operation for more information.

Electrical Load Management

The power management function is designed to monitor the vehicle electrical load and determine when the battery is potentially in a high discharge condition. This is accomplished by using a high accuracy battery voltage reading as an indicator of battery discharge rate. The following 6 levels of load management will execute in the load management control algorithm when there is a high discharge condition

1. The first action requests a vehicle idle speed increase to the engine control module (ECM) in order to raise alternator output.
2. The second action requests a greater vehicle idle speed increase to the ECM in order to raise alternator output.
3. The third action begins to shed vehicle loads in an attempt to remedy the heavy discharge condition.
4. The fourth action requests another vehicle idle speed increase to the ECM in order to raise further the alternator output.
5. The fifth action begins to shed further vehicle loads in an attempt to remedy the heavy discharge condition.
6. If the above 5 corrective actions fail, the sixth action of power management further sheds loads in a final attempt to remedy the high discharge condition.

Loads subject to reduction include the following

1. The A/C clutch
2. The heated mirrors
3. The heated seats
4. The rear defog
5. The HVAC blowers

The power mode master (PMM) calculates the battery temperature, voltage and charging rate at all times while the engine is running. The PMM calculates the battery temperature by factoring in

1. The current intake manifold air temperature compared to the last temperature recorded when the ignition switch was turned OFF
2. The current battery voltage compared to the last battery voltage recorded when the ignition switch was turned OFF
3. The length of time since the last battery temperature calculation

If the battery temperature is below set limits, the PMM institutes steps to control the load.

The PMM calculates the voltage of the battery by making constant measurements and using the measurements to calculate the true battery voltage. If the PMM detects a low voltage, the PMM institutes steps to control the load.

The PMM calculates the discharge rate, or draw, on the battery by making constant measurements and using the measurements to calculate the discharge rate in amp/hours. If the PMM detects a high current draw from the battery, the PMM institutes steps to control the load.

The PMM will either request an increase in the engine idle speed to the ECM or the PMM will cycle or turn OFF loads, called the load-shed function, in order to preserve the vehicle electrical system operation. The criteria used by the PMM to regulate this electrical load management are outlined below

Body Control System Description and Operation

Each load management function, either idle boost or load-shed, is discrete. No 2 functions are implemented at the same time.

During each load management function, the PMM checks the battery temperature, battery voltage and amp-hour calculations and determines if the PMM should implement a different power management function.

Idle Boost Functions

The PMM sends a serial data request to the ECM to increase the idle speed. The ECM then adjusts the idle speed by using a special program and idle speed ramp calculations in order to prevent driveability and safety concerns. The idle speed boost and cancel function will vary from vehicle to vehicle and from one moment to another on the same vehicle. This happens because the ECM responds to changes in the inputs from the sensors used to control the powertrain.

Load Shed Function

The PMM executes the load shed function, by controlling the relay coil of the following devices.

1. The A/C clutch
2. The heated mirrors
3. The heated seats
4. The rear defog
5. The HVAC blowers

DIM Wake-up/Sleep States

The dash integration module (DIM) is able to control or perform all of the DIM functions in the wake-up state. The DIM enters the sleep state when active control or monitoring of system functions has stopped, and the DIM has become idle again. The DIM must detect certain wake-up inputs before entering the wake-up state. The DIM monitors for these inputs during the sleep state, where the DIM is able to detect switch transitions that cause the DIM 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 DIM to enter a sleep state when the key is IN or OUT of the ignition.

The DIM 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. Door ajar switch
4. Headlamps are ON.
5. Hood ajar switch
6. Ignition is turned ON.
7. Key-in-ignition switch
8. Parklamps are ON.

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

1. Ignition switch is OFF.
2. No activity exists on the class 2 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 DIM will enter a low power or sleep condition. This condition indicates that the DIM, 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.

Rear Integration Module (RIM)

The various rear integration module (RIM) inputs and outputs are described in the corresponding functional areas as indicated on the RIM electrical schematics.

The RIM functions include the following

1. BTSI solenoid control
2. Class 2 communication requiring RIM interaction
3. Content theft deterrent
4. Fuel door control
5. Fuel level sensor input
6. Heated seat control
7. Intrusion sensor control
8. Key in ignition chime control
9. Performance shift control
10. Position lamp control
11. Park brake relay control
12. Rear defog relay control
13. Rear fog lamp relay control
14. Rear park assist chime control
15. Reverse lamp relay control
16. Reverse switch input w/manual transmission
17. Sunroof speed control
18. Traction mode switch input
19. Transmission shift inhibit
20. Trunk ajar input
21. Trunk entrapment sensor input
22. Trunk release relay control
23. Winter mode switch w/automatic transmission

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 dash integration module (DIM). The PMM receives 2 signals from the ignition switch.

To determine the correct power mode the PMM uses the following circuits

1. Accessory voltage
2. Run/crank voltage

2-Wire Ignition Switch Table

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 voltage, 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.

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 any door is opened, or until the RAP function timer reaches its shut-off limit.

The modules listed below all receive a RAP message from the dash integration module (DIM) over the serial data circuits. The DIM monitors the ignition switch position, battery condition and passenger compartment door status to determine whether RAP should be initiated. 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 DIM receives an input as a serial data message from any door module indicating the opening of a passenger compartment door.
2. The DIM receives a message from its internal timer indicating the end of the RAP period after 10 minutes.
3. The DIM 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 modules that participate in RAP power mode are

1. The digital radio receiver (DRR)
2. The driver door module (DDM)
3. The front passenger door module (FPDM)
4. The left rear door module (LRDM)
5. The radio
6. The radio antenna module
7. The rear integration module (RIM)
8. The right rear door module (RRDM)
9. The TV antenna module
10. The vehicle communication Interface module (VCIM)

See also:
• SIR DISABLING AND ENABLING ZONES
• Diagnostic System Check - Vehicle
• Testing for Intermittent Conditions and Poor Connections
• Circuit Testing
• Wiring Repairs
• Connector Repairs
• Ignition Switch Replacement
• DTC Symptom Description
• Master Electrical Component List
• Diagnostic Trouble Code (DTC) List - Vehicle
• GMLAN Wiring Repairs
• Checking Aftermarket Accessories
• Inline Harness Connector End Views
• Symptoms - Lighting Systems
• Radio/Audio System Schematics
• Antenna Module Programming and Setup
• OnStar Schematics
• OnStar Reconfiguration
• Digital Radio Receiver Setup
• Door Control Module Schematics
• DCM Programming/RPO Configuration
• ABS Schematics
• Suspension Controls Schematics
• Engine Controls Schematics
• Engine Controls Schematics
• Engine Control Module Programming and Setup (4.6L)
• Garage Door Opener Schematics
• Garage Door Opener Replacement
• Headlight Leveling Schematics
• Headlamp Leveling Module Replacement
• Driver Seat Schematics
• HVAC Schematics
• SIR Schematics
• Inflatable Restraint Sensing and Diagnostic Module Programming and Setup
• Inside Rearview Mirror Schematics
• Instrument Cluster Schematics
• Memory Seat Control Module Programming and Setup
• Object Detection Schematics
• Radio Setup
• Power Folding Seat Calibration
• Power Sunroof Schematics (Domestic)
• Theft Deterrent System Schematics
• Theft Deterrent Control Module Programming and Setup
• Automatic Transmission Controls Schematics
• Transmission Control Module Programming and Setup
• Trim Panel Replacement - Body Side Rear (w/o TB5)
• DTC B1000
• Control Module References
• Scan Tool Does Not Communicate with High Speed GMLAN Device
• Body Control System Description and Operation
• Retained Accessory Power (RAP) On After Timeout
• Retained Accessory Power (RAP) Inoperative