Data Communication System Chevrolet Chevy Express H1500

Data Communication Schematic Icons

Data Communication 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 . 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)

Scheme 1

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Scheme 8

Body Control Module (BCM) - C1 Connector & Terminal Parts Information

Body Control Module (BCM) - C1 Terminal Identification

Scheme 9

Body Control Module (BCM) - C2 Connector & Terminal Parts Information

Body Control Module (BCM) - C2 Terminal Identification

Scheme 10

Body Control Module (BCM) - C3 Connector & Terminal Parts Information

Body Control Module (BCM) - C3 Terminal Identification

Scheme 11

Body Control Module (BCM) - C4 Connector & Terminal Parts Information

Body Control Module (BCM) - C4 Terminal Identification

Scheme 12

Body Control Module (BCM) - C5 Connector & Terminal Parts Information

Body Control Module (BCM) - C5 Terminal Identification

Scheme 13

Body Control Module (BCM) - C6 (PRP) Connector & Terminal Parts Information

Body Control Module (BCM) - C6 (PRP) Terminal Identification

Scheme 14

Data Link Connector (DLC) Connector & Terminal Parts Information

Data Link Connector (DLC) Terminal Identification

DIAGNOSTIC CODE INDEX

DIAGNOSTIC CODE INDEX

Diagnostic Starting Point - Data Communications

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.

Diagnostic Instructions

1. Perform the «Diagnostic System Check - Vehicle»(/chevrolet/chevy-express-h1500/2003-2012/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-system-check-vehicle) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/chevrolet/chevy-express-h1500/2003-2012/remont/oem-general-information/#vehicle-diagnostic-information__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/chevrolet/chevy-express-h1500/2003-2012/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

DTC Descriptors

DTC B1000 Electronic Control Unit (ECU) Performance

Circuit/System Description

The control module runs a program to detect an internal fault when power up is commanded.

Conditions for Running the DTC

Ignition ON.

Conditions for Setting the DTC

The control module has detected an internal malfunction.

Action Taken When the DTC Sets

The control 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 ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.

Circuit/System Verification

Verify that DTC B1000 is not set.

1. If the DTC is set, perform the setup procedure on the control module. If the DTC resets replace the control module.

Repair Procedures

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for control module replacement, setup, and programming

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 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.

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 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

1. Perform the «Diagnostic System Check - Vehicle»(/chevrolet/chevy-express-h1500/2003-2012/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-system-check-vehicle) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/chevrolet/chevy-express-h1500/2003-2012/remont/oem-general-information/#vehicle-diagnostic-information__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/chevrolet/chevy-express-h1500/2003-2012/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

The high speed GMLAN serial data circuits are 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. The high speed GMLAN serial data circuits also connect directly to the data link connector (DLC).

Conditions for Running the DTCs

1. Supply voltage to the modules are in the normal operating range.
2. The vehicle power mode requires serial data communications.

The module setting the DTC has attempted to establish communications on the GMLAN circuits more than 3 times.

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 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 of 50, without a repeat of the malfunction.

1. An intermittent condition is likely to be caused by a short on the high speed GMLAN serial data circuits.
2. This DTC cannot be retrieved with a current status. Diagnosis is accomplished using the symptom «Scan Tool Does Not Communicate with High Speed GMLAN Device»(/chevrolet/chevy-express-h1500/2003-2012/remont/communication-devices/#data-communication-system) .
3. Refer to «Data Link References»(/chevrolet/chevy-express-h1500/2003-2012/remont/communication-devices/#data-communication-system__data-link-references) for the specific modules using high speed GMLAN serial data.

Perform the Diagnostic Repair Verification after completing the repair.

1. Perform the «Diagnostic System Check - Vehicle»(/chevrolet/chevy-express-h1500/2003-2012/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-system-check-vehicle) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/chevrolet/chevy-express-h1500/2003-2012/remont/oem-general-information/#vehicle-diagnostic-information__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/chevrolet/chevy-express-h1500/2003-2012/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-procedure-instructions) provide an overview of each diagnostic category.

Diagnostic Fault Information

DTC U0100-U0299

Modules connected to the high and low 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 periodic messages are used by the receiver module as an availability indication of the transmitter module. Each message contains the identification number of the transmitter module.

1. The system voltage is between 9-16 volts.
2. The vehicle power mode requires serial data communications.
3. The DTC U0073 is not set as current.

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

The module setting the DTC uses default values for the missing parameters.

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 of 50, without a repeat of the malfunction.

Use the DTC Descriptor list to determine the module which is not communicating. If there are multiple non-communicating modules in series on high speed GMLAN, choose the one closest to the data link connector (DLC) for this diagnostic.

Reference Information

Schematic Reference

1. «Data Communication Schematics»(/chevrolet/chevy-express-h1500/2003-2012/remont/communication-devices/#data-communication-system)
2. «Control Module References»(/chevrolet/chevy-express-h1500/2003-2012/remont/communication-devices/#programming-and-setup-all-systems__control-module-references)

Connector End View Reference

Master Electrical Component List

Electrical Information Reference

1. «Circuit Testing»(/chevrolet/chevy-express-h1500/2003-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-troubleshooting-diagnosis__circuit-testing)
2. «Connector Repairs»(/chevrolet/chevy-express-h1500/2003-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-troubleshooting-diagnosis__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/chevy-express-h1500/2003-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-troubleshooting-diagnosis__testing-for-intermittent-conditions-and-poor)
4. «Wiring Repairs»(/chevrolet/chevy-express-h1500/2003-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-troubleshooting-diagnosis__wiring-repairs)
5. «GMLAN Wiring Repairs»(/chevrolet/chevy-express-h1500/2003-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-troubleshooting-diagnosis)

Circuit/System Testing

1. Using the DTC Descriptor and Diagnostic Aids determine which module is not communicating.
2. Ignition OFF, disconnect the harness connector at the module that is not communicating.
3. Test for less than 0.5 ohm of resistance between each ground circuit of the module that is not communicating and ground. If greater than 0.5 ohm, repair the open/high resistance in the ground circuit.
4. Test for battery voltage between each battery positive voltage circuit of the module that is not communicating and ground. If less than battery voltage, repair the short to ground or open/high resistance in the battery positive voltage circuit.
5. Ignition ON, test for battery voltage between each ignition circuit of the module that is not communicating and ground. If less than battery voltage, repair the short to ground or open/high resistance in the ignition circuit.
6. Ignition OFF, disconnect the harness connector at the module that reported the no communication DTC.
7. Ignition OFF, test for less than 0.5 ohm of resistance in each serial data circuit between the module that is not communicating and the module that reported the DTC. If greater than 0.5 ohm, repair the open/high resistance in the serial data circuit.
8. If all tests normal, replace the module that is not communicating.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for non-communicating module replacement, setup, and programming

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 or U1255 are 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. The following modules communicate on the class 2 serial data line

1. The body control module (BCM)
2. The chime module
3. The electronic brake control module (EBCM)
4. The inflatable restraint sensing and diagnostic module (SDM)
5. The instrument panel cluster (IPC)
6. The powertrain control module (PCM)
7. The remote control door lock receiver (RCDLR)
8. The radio
9. The vehicle communication interface module (VCIM), w/UE1

This diagnostic procedure supports the following DTCs

1. DTC U1000 Class 2 Data Link
2. DTC U1255 Class 2 Data Link

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 or U1255 are set current by the other modules. If the malfunction occurs when the modules are not communicating, only U1000 or U1255 are set.

Test Description

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 or U1255.
2. 3: The modules not communicating are the likely cause of U1000 or U1255. 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 or U1255 may have done so due to some other condition.
6. 15: The module which set U1000 or U1255 is the likely cause of the malfunction.

DTC U1000 and U1255

1. Perform the «Diagnostic System Check - Vehicle»(/chevrolet/chevy-express-h1500/2003-2012/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-system-check-vehicle) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/chevrolet/chevy-express-h1500/2003-2012/remont/oem-general-information/#vehicle-diagnostic-information__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/chevrolet/chevy-express-h1500/2003-2012/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

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. 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.

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 5 seconds, a DTC U1xxx, where xxx is equal to the 3-digit identification number, is set.

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.

The module(s) is never signaled, therefore the specific subsystem(s) will not function.

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 of 50, without a repeat of the malfunction.

1. Use the DTC Descriptor list above to determine the module which is not communicating.
2. Some modules may not have internal protection for specific voltage outputs and may open a battery positive voltage or ignition voltage source fuse. If a voltage input fuse is open and no short is found in that circuit, ensure that no module output voltage circuit is shorted to ground before replacing the module.
3. This diagnostic can be used for any module that should communicate with Class 2 serial data providing the vehicle is equipped with the option that uses that module.

Schematic Reference

1. «Data Communication Schematics»(/chevrolet/chevy-express-h1500/2003-2012/remont/communication-devices/#data-communication-system)
2. «Control Module References»(/chevrolet/chevy-express-h1500/2003-2012/remont/communication-devices/#programming-and-setup-all-systems__control-module-references)

Connector End View Reference

Master Electrical Component List

Electrical Information Reference

1. «Circuit Testing»(/chevrolet/chevy-express-h1500/2003-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-troubleshooting-diagnosis__circuit-testing)
2. «Connector Repairs»(/chevrolet/chevy-express-h1500/2003-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-troubleshooting-diagnosis__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/chevy-express-h1500/2003-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-troubleshooting-diagnosis__testing-for-intermittent-conditions-and-poor)
4. «Wiring Repairs»(/chevrolet/chevy-express-h1500/2003-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-troubleshooting-diagnosis__wiring-repairs)

1. If U1064 is set in the ECM, attempt to communicate with the BCM. Communication should not be available. If the BCM can communicate, test the Class 2 serial data circuit from the ECM for open/high resistance. If the circuits test normal, replace the ECM.
2. Using the DTC Descriptor and Diagnostic Aids above, determine the module that is not communicating that should be tested.
3. Ignition OFF, disconnect the harness connector of the module that is not communicating.
4. Ignition ON, verify that a test lamp illuminates between all battery positive voltage circuits and ground. If the test lamp does not illuminate, repair the circuit for a short to ground or an open/high resistance. If the circuit fuse is open, also test the positive voltage outputs of the module for a short to ground. If the circuits test normal, replace the faulty module.
5. Verify that a test lamp illuminates between all ignition voltage circuits and ground. If the test lamp does not illuminate, repair the circuit for a short to ground or an open/high resistance. If the circuit fuse is open, also test the positive voltage outputs of the module for a short to ground. If the circuits test normal, replace the faulty module.
6. Test for less than 1 ohm of resistance between the module ground circuits and ground. If greater than 1 ohm, repair the ground circuit for an open.
7. Test for less than 1 ohm of resistance in the Class 2 serial data circuit between the non-communicating module and the module that displays the DTC. If greater than 1 ohm of resistance, test the Class 2 serial data circuit for open/high resistance.
8. If all circuits test normal, replace the module that is not communicating.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for module replacement, setup, and programming

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

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 DTC 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»(/chevrolet/chevy-express-h1500/2003-2012/remont/communication-devices/#data-communication-system) .
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»(/chevrolet/chevy-express-h1500/2003-2012/remont/communication-devices/#data-communication-system) .

Symptoms - Data Communications

1. Perform the «Diagnostic System Check - Vehicle»(/chevrolet/chevy-express-h1500/2003-2012/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-system-check-vehicle) 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: «Body Control System Description and Operation»(/chevrolet/chevy-express-h1500/2003-2012/remont/communication-devices/#data-communication-system) «Data Link Communications Description and Operation»(/chevrolet/chevy-express-h1500/2003-2012/remont/communication-devices/#data-communication-system)

Visual/Physical Inspection

1. Inspect for aftermarket devices which could affect the operation of the systems. Refer to «Checking Aftermarket Accessories»(/chevrolet/chevy-express-h1500/2003-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-troubleshooting-diagnosis__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»(/chevrolet/chevy-express-h1500/2003-2012/remont/communication-devices/#data-communication-system)
2. «Scan Tool Does Not Communicate with High Speed GMLAN Device»(/chevrolet/chevy-express-h1500/2003-2012/remont/communication-devices/#data-communication-system)
3. «Scan Tool Does Not Communicate with Class 2 Device»(/chevrolet/chevy-express-h1500/2003-2012/remont/communication-devices/#data-communication-system)

1. Perform the «Diagnostic System Check - Vehicle»(/chevrolet/chevy-express-h1500/2003-2012/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-system-check-vehicle) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/chevrolet/chevy-express-h1500/2003-2012/remont/oem-general-information/#vehicle-diagnostic-information__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/chevrolet/chevy-express-h1500/2003-2012/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

Scan Tool Does Not Power Up

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

1. 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.
2. If the battery positive voltage, ground circuits and connections of the DLC are functioning properly, the malfunction must be due to the scan tool/CANdi module.
3. Use the DMM MIN/MAX function to capture/locate intermittent conditions.

Schematic Reference

Data Communication Schematics

Connector End View Reference

Data Communication Connector End Views

Electrical Information Reference

1. «Circuit Testing»(/chevrolet/chevy-express-h1500/2003-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-troubleshooting-diagnosis__circuit-testing)
2. «Connector Repairs»(/chevrolet/chevy-express-h1500/2003-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-troubleshooting-diagnosis__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/chevy-express-h1500/2003-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-troubleshooting-diagnosis__testing-for-intermittent-conditions-and-poor)
4. «Wiring Repairs»(/chevrolet/chevy-express-h1500/2003-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-troubleshooting-diagnosis__wiring-repairs)

1. Ignition ON, test for battery voltage between the battery positive voltage circuit of the DLC and ground. If less than battery voltage, repair the voltage supply circuit for a short to ground or an open/high resistance.
2. Test for less than 1.0 ohm of resistance between the ground circuit of the DLC and ground. If greater than 1.0 ohm, repair the ground circuit for an open/high resistance.
3. If all tests normal, refer to the scan tool/CANdi module user guide.

Perform the Diagnostic Repair Verification after completing the repair.

1. Perform the «Diagnostic System Check - Vehicle»(/chevrolet/chevy-express-h1500/2003-2012/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-system-check-vehicle) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/chevrolet/chevy-express-h1500/2003-2012/remont/oem-general-information/#vehicle-diagnostic-information__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/chevrolet/chevy-express-h1500/2003-2012/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

Scan Tool Does Not Communicate with Class 2 Device

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 class 2 serial data circuit uses SP 205 (splice pack comb) as a common connection between some modules and the DLC. DTCs may be set due to this symptom and during this diagnostic procedure.

1. Use the «Data Link References»(/chevrolet/chevy-express-h1500/2003-2012/remont/communication-devices/#data-communication-system__data-link-references) to identify the class 2 serial data modules.
2. This test is used for a total class 2 communication failure. If only 1 module is not communicating and sets no DTC, ensure that the vehicle is equipped with the module, then use «DTC U1001-U1254»(/chevrolet/chevy-express-h1500/2003-2012/remont/communication-devices/#data-communication-system) for diagnostics.
3. 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.
4. An open in the class 2 serial data circuit between SP 205 and a module(s) will only effect the specific module(s). This type of failure will set a loss of communication DTC for each module effected, and the other modules will still communicate.
5. An open between the data link connector (DLC) and SP 205 will only effect the communication with the scan tool. The vehicle modules will still communicate, and the vehicle will start.
6. The engine may not start when there is a total malfunction of the class 2 serial data circuit. The following conditions may cause a total loss of low speed GMLAN data communication: The low speed GMLAN serial data circuit shorted to ground or voltage. A module internal malfunction that causes a short to voltage or ground on the low speed GMLAN circuit. An open in the DLC ground circuit may cause a scan tool loss of communication, while the modules still communicate.
7. Use the DMM MIN/MAX function to capture/locate intermittent conditions.
8. When the class 2 serial data circuit is shorted to ground or to voltage, the following DTCs may set: U1300 U1301 U1305

Schematic Reference

1. «Data Communication Schematics»(/chevrolet/chevy-express-h1500/2003-2012/remont/communication-devices/#data-communication-system)
2. «Control Module References»(/chevrolet/chevy-express-h1500/2003-2012/remont/communication-devices/#programming-and-setup-all-systems__control-module-references)

Connector End View Reference

Master Electrical Component List

Description and Operation

Data Link Communications Description and Operation

Electrical Information Reference

1. «Circuit Testing»(/chevrolet/chevy-express-h1500/2003-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-troubleshooting-diagnosis__circuit-testing)
2. «Connector Repairs»(/chevrolet/chevy-express-h1500/2003-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-troubleshooting-diagnosis__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/chevy-express-h1500/2003-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-troubleshooting-diagnosis__testing-for-intermittent-conditions-and-poor)
4. «Wiring Repairs»(/chevrolet/chevy-express-h1500/2003-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-troubleshooting-diagnosis__wiring-repairs)

1. Test for less than 1.0 ohm of resistance between the DLC ground circuit terminal 5 and ground. If greater than 1.0 ohm, test the ground circuit for open/high resistance.
2. Ignition OFF, disconnect the harness connector (splice pack comb) at SP 205. Install a 3-amp fused jumper wire between SP 205 pin A and pin M, harness side.
3. Ignition ON, with a scan tool, attempt to communicate with the body control module (BCM). Communication should be available. If no communication, test the serial data circuit for a short to ground, a short to voltage or an open/high resistance between the BCM and the DLC. If the circuit tests normal, replace the BCM.
4. Install another 3-amp fused jumper wire to SP 205 pin A, harness side.
5. With BCM communications established, use the other end of the jumper wire to connect all other pins, harness side, one at a time and verify that communication remains available to the BCM. IMPORTANT: Allow communications for 5 seconds after connecting a module with the jumper to determine if communication is interrupted or not. If communication is interrupted after connecting an individual module at SP 205, test the serial data circuit between SP 205 and the last module connected for a short to ground and short to voltage. If the circuit tests normal, replace the module that caused no communication.

Perform the Diagnostic Repair Verification after completing the repair.

1. «Control Module References»(/chevrolet/chevy-express-h1500/2003-2012/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for module replacement, setup, and programming
2. «GMLAN Wiring Repairs»(/chevrolet/chevy-express-h1500/2003-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-troubleshooting-diagnosis)

The GMLAN serial data circuits are 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. The GMLAN serial data circuits also connect directly to the data link connector (DLC).

Modules connected to the GMLAN serial data circuits monitor communications during normal vehicle operation, where operation information is exchanged among the modules.

A CANdi Module is necessary between the scan tool and the ALDL and acts as a transceiver for the scan tool communications with the GMLAN modules. If a CANdi module is not used there may be no communication messages for the specific GMLAN modules.

The scan tool communicates with the following modules on the high speed GMLAN serial data circuits

1. Auxiliary Heater Control Module (FOH) (w/K08, Coolant Heater)
2. Engine control module (ECM)
3. Glow plug control module (GPCM)
4. Transmission control module (TCM)

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

Scan Tool Does Not Communicate with High Speed GMLAN Device

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 right side knee bolster trim panel. Refer to «Passenger Knee Bolster Replacement»(/chevrolet/chevy-express-h1500/2003-2012/remont/exteriorinterior-trim/#instrument-panel-trim-and-console-trim) .
2. Disconnect the electrical connectors (2) from the body control module (BCM) (1).
3. Release the tabs (2) retaining the BCM (1) to the bracket.
4. Remove the BCM (1) from the vehicle.

Installation Procedure

1. Install the BCM (1) into the bracket. Ensure the BCM (1) is engaged in the bracket, under the retaining tabs (2).
2. Connect the electrical connectors (2) to the BCM (1).
3. Install the right side knee bolster trim panel. Refer to «Passenger Knee Bolster Replacement»(/chevrolet/chevy-express-h1500/2003-2012/remont/exteriorinterior-trim/#instrument-panel-trim-and-console-trim) .
4. If you replaced the BCM, program the module. Refer to «Body Control Module Programming and Setup»(/chevrolet/chevy-express-h1500/2003-2012/remont/communication-devices/#programming-and-setup-all-systems) .
5. Refer to «Control Module References»(/chevrolet/chevy-express-h1500/2003-2012/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for programming and setup information.

BCM Functions

The body control module (BCM) performs multiple body control functions. The BCM can control devices directly connected to its outputs based on input information. The BCM evaluates this information and controls certain body control systems by commanding outputs ON or OFF. The BCM control inputs can be

1. Sensors and switches that are directly connected to the BCM
2. Class 2 serial data received from other control modules connected to the class 2 serial data link

The BCM is also capable of controlling other vehicle systems that are not directly wired to the BCM. The BCM does this by sending specific messages on the class 2 serial data link. The control module capable of performing the required function will respond to the BCM message.

The BCM controls these functions

1. Audible warnings-Refer to «Audible Warnings Description and Operation»(/chevrolet/chevy-express-h1500/2003-2012/remont/gauges-instrument-panels/#instrument-panel-system-displays-and-gauges__audible-warnings-description-and-operation) .
2. Automatic door locks-Refer to «Power Door Locks Description and Operation»(/chevrolet/chevy-express-h1500/2003-2012/remont/door-locks-anti-theft-systems/#door-lock-systems-door-handles) .
3. Interior lighting-Refer to «Interior Lighting Systems Description and Operation»(/chevrolet/chevy-express-h1500/2003-2012/remont/exterior-lights/#lighting-system) .
4. Keyless entry-Refer to «Keyless Entry System Description and Operation»(/chevrolet/chevy-express-h1500/2003-2012/remont/door-locks-anti-theft-systems/#keyless-entry-system-and-remote-functions__keyless-entry-system-description-and-operation) .
5. Passlock theft deterrent-Refer to «Immobilizer Description and Operation»(/chevrolet/chevy-express-h1500/2003-2012/remont/door-locks-anti-theft-systems/#immobilizer-system) .
6. Retained accessory power (RAP)-Refer to «Retained Accessory Power (RAP) Description and Operation»(/chevrolet/chevy-express-h1500/2003-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-introduction) .

Power Mode

The body control module (BCM) is the power mode master (PMM). Refer to Power Mode Description and Operation for more information.

The serial data communication among the control modules is performed through multiple serial data communication links. The class 2 serial data line is always present. The high speed GMLAN serial data lines are also present for the diesel option. The data link connector (DLC) allows a scan tool to communicate with the modules on class 2 or high speed GMLAN serial data lines. In order for the scan tool to communicate with the modules on high speed GMLAN link, a CANdi module is needed. The CANdi module behaves as an interface between the scan tool and the high speed GMLAN data link.

Data Link Connector (DLC)

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. High speed GMLAN serial data bus (+) at terminal 6
6. High speed GMLAN serial data bus (-) at terminal 14

Class 2 Serial Data Line

Class 2 serial data is transmitted on a single wire at an average of 10.4 kbps. 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 a lost communication DTC associated with the loss of SOH for 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.

The class 2 serial data line on this vehicle is a star configuration. The following modules communicate on the class 2 serial data line

1. The audible alert control module (CHIME) (w/UL5)
2. The body control module (BCM)
3. The electronic brake control module (EBCM)
4. The inflatable restraint sensing and diagnostic module (SDM)
5. The instrument panel cluster (IPC)
6. The powertrain/engine control module (PCM/ECM)
7. The radio
8. The remote control door lock receiver (RCDLR)
9. The engine control module (ECM) (Diesel)

The class 2 serial data line allows a scan tool to communicate with these modules for testing purposes, checking for DTCs, and to activate/enable/disable functions. These class 2 serial data circuits are bussed together at SP200-Refer to Master Electrical Component List for SP200 location.

High Speed GMLAN Serial Data Line (Diesel only)

The data link connector (DLC) allows a scan tool to communicate with the high speed GMLAN serial data circuit through the CANdi module. The serial data is transmitted on two twisted wires that allow speed up to 500 Kbps. The twisted pair is terminated with two 120 ohm resistors, one is internal to the transmission control module (TCM) and the other is internal to the engine control module (ECM). 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. 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's 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 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.

The engine control module (ECM) is functionally communicating on both class 2 and high speed GMLAN data links. However the diagnostic communication of the above modules with the scan tool is performed on class 2 data link only. All DTCs set by the high speed GMLAN modules, are reported by the ECM on class 2. Data displaying, output controls and programming of the control modules connected to high speed GMLAN only, is performed through high speed GMLAN link.

Several of the GMLAN serial data modules are in a linear configuration from SP250. The engine control module is separated from the linear configuration at SP250. If not equipped with an auxiliary heater control module (FOH) (w/K08, coolant heater) a jumper harness is in its place. Refer to Master Electrical Component List for SP250 location.

The following modules are connected to the link in a linear configuration

1. The auxiliary heater control module (FOH) (w/K08, coolant heater)
2. The glow plug control module (GPCM)
3. The transmission control module (TCM)

See also:
• SIR Disabling and Enabling
• Diagnostic System Check - Vehicle
• Strategy Based Diagnosis
• Diagnostic Procedure Instructions
• Diagnostic Repair Verification
• Control Module References
• Master Electrical Component List
• Circuit Testing
• Connector Repairs
• Testing for Intermittent Conditions and Poor Connections
• Wiring Repairs
• GMLAN Wiring Repairs
• Diagnostic Trouble Code (DTC) List - Vehicle
• Checking Aftermarket Accessories
• Passenger Knee Bolster Replacement
• Body Control Module Programming and Setup
• Audible Warnings Description and Operation
• Power Door Locks Description and Operation
• Interior Lighting Systems Description and Operation
• Keyless Entry System Description and Operation
• Immobilizer Description and Operation
• Retained Accessory Power (RAP) Description and Operation
• DTC B1000
• Data Link References