Data Communication System Chevrolet Colorado I

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Scheme 6

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/colorado/i-2004-2012/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-system-check-vehicle) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/chevrolet/colorado/i-2004-2012/remont/oem-general-information/#vehicle-diagnostic-information__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/chevrolet/colorado/i-2004-2012/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

Circuit/System Description

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

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 of 50, 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.
2. If stored only as a history DTC and not retrieved as a current DTC, do not replace the module.
3. If this DTC is retrieved as both a current and history DTC, replace the module that set the DTC.

Circuit/System Verification

If this DTC is retrieved as a current DTC, replace the module that set the DTC.

Repair Procedures

Perform the Diagnostic Repair Verification after completing the repair.

Control Module References for module replacement, setup, and programming

1. Perform the «Diagnostic System Check - Vehicle»(/chevrolet/colorado/i-2004-2012/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-system-check-vehicle) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/chevrolet/colorado/i-2004-2012/remont/oem-general-information/#vehicle-diagnostic-information__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/chevrolet/colorado/i-2004-2012/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

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

Battery voltage is between 9-16 volts and data link communications operate normally.

The control module is not configured properly.

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. Program or configure the module or related module that set DTC B1001. The module should successfully configure. If the module will not configure, replace the module that set the DTC.
2. With a scan tool, clear the DTC.
3. Ignition OFF, remove the scan tool, open and close the drivers door.
4. Wait 60 seconds, then recheck for DTCs. DTC B1001 should not set. If DTC B1001 sets, replace the module.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

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

1. Perform the «Diagnostic System Check - Vehicle»(/chevrolet/colorado/i-2004-2012/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-system-check-vehicle) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/chevrolet/colorado/i-2004-2012/remont/oem-general-information/#vehicle-diagnostic-information__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/chevrolet/colorado/i-2004-2012/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

The electrically erasable programmable read-only memory (EEPROM) check sum error detection is handled inside the control module.

The control module runs the program to detect an EEPROM checksum error after each wake-up. The only requirements are battery positive voltage and ground.

The control module retains an inverse copy of the digital value stored in certain blocks of memory in the EEPROM. The control 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 control module reverts to base operation values programmed for those blocks of data that have failed the check sum test.

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

Reference Information

Schematic Reference

Data Communication Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Data Link Communications Description and Operation

Electrical Information Reference

1. «Circuit Testing»(/chevrolet/colorado/i-2004-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__circuit-testing)
2. «Connector Repairs»(/chevrolet/colorado/i-2004-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/colorado/i-2004-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__testing-for-intermittent-conditions-and-poor)
4. «Wiring Repairs»(/chevrolet/colorado/i-2004-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__wiring-repairs)

Scan Tool References

Control Module References for scan tool information

1. With a scan tool, clear the DTC. If the DTC will not clear, replace the module that set the DTC.
2. Ignition OFF, remove the scan tool, open and close the drivers door.
3. Wait 60 seconds, verify DTC B1009 is not set. If the DTC is set, replace the module.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

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

1. Perform the «Diagnostic System Check - Vehicle»(/chevrolet/colorado/i-2004-2012/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-system-check-vehicle) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/chevrolet/colorado/i-2004-2012/remont/oem-general-information/#vehicle-diagnostic-information__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/chevrolet/colorado/i-2004-2012/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

Diagnostic Fault Information

DTC U1000 and U1255

Circuit Description

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

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

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

The module uses a default value for the missing parameter.

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

If a malfunction such as an open fuse to a module occurs while serial data communication is active, a Lost Communication DTC for the specific module is set as a current DTC in other modules. When all serial data communication becomes inactive, the current Lost Communication DTC is cleared, but the history DTC remains. When serial data communication resumes, the module with the open fuse will not be learned by the other modules, so DTC U1000 or U1255 is set as current by the other modules.

In the event of a malfunction occurrence while serial data communication is inactive, DTC U1000 or U1255 is set without a loss of communication DTC for the specific module.

Schematic Reference

Data Communication Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Data Link Communications Description and Operation

Electrical Information Reference

1. «Circuit Testing»(/chevrolet/colorado/i-2004-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__circuit-testing)
2. «Connector Repairs»(/chevrolet/colorado/i-2004-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/colorado/i-2004-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__testing-for-intermittent-conditions-and-poor)
4. «Wiring Repairs»(/chevrolet/colorado/i-2004-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Testing

1. Verify that no DTC within the range of U1001-U1254 exists as current or history in any module. If any DTC within the range of U1001-U1254 does exist, refer to «Diagnostic Trouble Code (DTC) List - Vehicle»(/chevrolet/colorado/i-2004-2012/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-trouble-code-dtc-list) .
2. Ignition OFF, disconnect the harness connector of the module that is not communicating.
3. Ignition ON, verify that a test lamp illuminates between all battery positive voltage circuits and ground. If the test lamp does not illuminate, test 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.
4. Verify that a test lamp illuminates between all ignition voltage circuits and ground. If the test lamp does not illuminate, test 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. Test for less than 1 ohm between the module ground circuits and ground. If greater than the specified range, test the ground circuit for open/high resistance.
6. Test for less than 1 ohm in the class 2 serial data circuit(s) between the non-communicating module and the module that displays the DTC. If greater than the specified range, test the serial data circuit(s) for open/high resistance.
7. If all circuits test normal, replace the module that is not communicating.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «GMLAN Wiring Repairs»(/chevrolet/colorado/i-2004-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis)
2. «Control Module References»(/chevrolet/colorado/i-2004-2012/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for module replacement, setup, and programming

1. Perform the «Diagnostic System Check - Vehicle»(/chevrolet/colorado/i-2004-2012/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-system-check-vehicle) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/chevrolet/colorado/i-2004-2012/remont/oem-general-information/#vehicle-diagnostic-information__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/chevrolet/colorado/i-2004-2012/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

Data Communication Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Data Link Communications Description and Operation

Electrical Information Reference

1. «Circuit Testing»(/chevrolet/colorado/i-2004-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__circuit-testing)
2. «Connector Repairs»(/chevrolet/colorado/i-2004-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/colorado/i-2004-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__testing-for-intermittent-conditions-and-poor)
4. «Wiring Repairs»(/chevrolet/colorado/i-2004-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

1. Ignition OFF, disconnect the harness connector of the module that is not communicating.
2. Ignition ON, verify that a test lamp illuminates between all battery positive voltage circuits and ground. If the test lamp does not illuminate, test 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.
3. Verify that a test lamp illuminates between all ignition voltage circuits and ground. If the test lamp does not illuminate, test 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.
4. Test for less than 1 ohm between the module ground circuits and ground. If greater than the specified range, test the ground circuit for an open.
5. Test for less than 1 ohm in the class 2 serial data circuit between the non-communicating module and the module that displays the DTC. If greater than the specified range, test the class 2 serial data circuit for open/high resistance.
6. 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

1. Perform the «Diagnostic System Check - Vehicle»(/chevrolet/colorado/i-2004-2012/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-system-check-vehicle) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/chevrolet/colorado/i-2004-2012/remont/oem-general-information/#vehicle-diagnostic-information__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/chevrolet/colorado/i-2004-2012/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

DTC U1300, U1301, or U1305

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 high or low voltage 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.

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.

Conditions for Setting the DTCs

The class 2 serial data circuit is shorted high or low for approximately 3 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.

1. These DTCs cannot be retrieved with a current status. Diagnosis of current DTCs is accomplished via the symptom «Scan Tool Does Not Communicate with Class 2 Device»(/chevrolet/colorado/i-2004-2012/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.

Symptoms - Data Communications

1. Perform the «Diagnostic System Check - Vehicle»(/chevrolet/colorado/i-2004-2012/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 the following: «Data Link Communications Description and Operation»(/chevrolet/colorado/i-2004-2012/remont/communication-devices/#data-communication-system) «Body Control System Description and Operation»(/chevrolet/colorado/i-2004-2012/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/colorado/i-2004-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-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/colorado/i-2004-2012/remont/communication-devices/#data-communication-system)
2. «Scan Tool Does Not Communicate with Class 2 Device»(/chevrolet/colorado/i-2004-2012/remont/communication-devices/#data-communication-system)

1. Perform the «Diagnostic System Check - Vehicle»(/chevrolet/colorado/i-2004-2012/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-system-check-vehicle) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/chevrolet/colorado/i-2004-2012/remont/oem-general-information/#vehicle-diagnostic-information__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/chevrolet/colorado/i-2004-2012/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.

Schematic Reference

Data Communication Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Data Link Communications Description and Operation

Electrical Information Reference

1. «Circuit Testing»(/chevrolet/colorado/i-2004-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__circuit-testing)
2. «Connector Repairs»(/chevrolet/colorado/i-2004-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/colorado/i-2004-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__testing-for-intermittent-conditions-and-poor)
4. «Wiring Repairs»(/chevrolet/colorado/i-2004-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

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

1. Perform the «Diagnostic System Check - Vehicle»(/chevrolet/colorado/i-2004-2012/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-system-check-vehicle) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/chevrolet/colorado/i-2004-2012/remont/oem-general-information/#vehicle-diagnostic-information__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/chevrolet/colorado/i-2004-2012/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. DTCs may be set due to this symptom and during this diagnostic procedure.

1. 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/colorado/i-2004-2012/remont/communication-devices/#data-communication-system) for diagnostics.
2. An open in the class 2 serial data circuit between the DLC and the BCM will only effect the scan tool communication and will not effect module to module communication
3. An open between the data link connector (DLC) and The BCM will only effect the communication with the scan tool. The vehicle modules will still communicate, and the vehicle will start.
4. 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 class 2 serial data circuit shorted to ground or voltage. A module internal malfunction that causes a short to voltage or ground on the class 2 serial data circuit.
5. When the class 2 serial data circuit is shorted to ground or to voltage, the following DTCs may set as history. If the short is removed and communication returns, these DTCs indicate an intermittent condition. U1300 U1301 U1305

Schematic Reference

Data Communication Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Data Link Communications Description and Operation

Electrical Information Reference

1. «Circuit Testing»(/chevrolet/colorado/i-2004-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__circuit-testing)
2. «Connector Repairs»(/chevrolet/colorado/i-2004-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/colorado/i-2004-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__testing-for-intermittent-conditions-and-poor)
4. «Wiring Repairs»(/chevrolet/colorado/i-2004-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__wiring-repairs)

Scan Tool Reference

Control Module References for Scan Tool Information

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 module harness connectors listed one at a time, attempting to communicate with the BCM after each disconnect. Communication should not be available. Digital radio receiver - X1 Vehicle communication interface module (VCIM) - X2 Transfer case shift control module - X2 Instrument panel cluster (IPC) - X1 Radio - X1, X2 Powertrain control module (PCM) -X1 Inflatable restraint sensing and diagnostic module (SDM) - X1 Electronic brake control module (EBCM) - X1 Generator battery control module - X1 If communications are available after a module disconnect, test all the serial data circuits to the last module disconnected for a short to ground or short to voltage. If the circuits test normal, replace the last module disconnected.
3. Ignition OFF, disconnect the BCM harness connector X1 and X2.
4. Connect a test lamp between B+ and the following BCM connector terminals. The test lamp should not illuminate. X2, terminal A38 X2, terminal A39 X2, terminal A44 X1, terminal A41 X1, terminal A42 X1, terminal A47 If the test lamp illuminates, test the serial data circuit for a short to ground.
5. Connect a test lamp between ground and the following BCM connector terminals. The test lamp should not illuminate. X2, terminal A38 X2, terminal A39 X2, terminal A44 X1, terminal A41 X1, terminal A42 X1, terminal A47 If the test lamp illuminates, test the serial data circuit for a short to voltage.
6. If the circuits test normal, replace the BCM.

Perform the Diagnostic Repair Verification after completing the repair.

1. «Control Module References»(/chevrolet/colorado/i-2004-2012/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for module replacement, setup, and programming
2. «GMLAN Wiring Repairs»(/chevrolet/colorado/i-2004-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis)

1. Perform the «Diagnostic System Check - Vehicle»(/chevrolet/colorado/i-2004-2012/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-system-check-vehicle) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/chevrolet/colorado/i-2004-2012/remont/oem-general-information/#vehicle-diagnostic-information__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/chevrolet/colorado/i-2004-2012/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

Scan Tool Does Not Communicate with High Speed GMLAN Device

Modules connected to the GMLAN serial data circuit monitor for serial data communications on the GMLAN network during normal vehicle operation. Operating information and commands are exchanged among the modules. The high speed GMLAN serial data buss uses two 120 ohm terminating resistors that are in parallel with the high speed GMLAN (+) and (-) circuits. One of the resistors is connected near the data link connector (DLC) end of the link and the other is internal to the ECM/PCM, end of the link. When a module detects a bus-off condition a DTC U2100 will be set. This DTC can be retrieved as history only.

1. When testing for a short between the high speed GMLAN (+) and (-) circuits (ECM/PCM disconnected), a resistance reading of 120 ohms is normal. To test for shorts to voltage or ground in the high speed GMLAN (+) and (-) circuits ensure that all modules, resistors and the scan tool are disconnected from the buss. A normal resistance reading across the high speed GMLAN buss with the resistors, all module and scan tool disconnected is infinite ohms.
2. The engine may not start when there is a total malfunction of the high speed GMLAN serial data bus. The following conditions may cause a total loss of high speed GMLAN data communication: A short between high speed GMLAN (+) and high speed GMLAN (-) circuits Any of the high speed GMLAN serial data circuits shorted to ground or voltage A module internal malfunction that causes a short to voltage or ground on the high speed GMLAN circuits

Schematic Reference

Data Communication Schematics

Connector End View Reference

Component Connector End Views

Description and Operation Reference

Data Link Communications Description and Operation

Electrical Information Reference

1. «Circuit Testing»(/chevrolet/colorado/i-2004-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__circuit-testing)
2. «Connector Repairs»(/chevrolet/colorado/i-2004-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/colorado/i-2004-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__testing-for-intermittent-conditions-and-poor)
4. «Wiring Repairs»(/chevrolet/colorado/i-2004-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__wiring-repairs)

Scan Tool Reference

Control Module References for Scan Tool Information

1. Test for less than 1.0 ohm of resistance between the DLC ground circuit terminal 5 and ground. If greater than the specified range, test the ground circuit for open/high resistance.
2. Ignition OFF, disconnect the harness connector X 3 at the engine control module (ECM).
3. Test for less than 1 ohm of resistance between each ground circuit of the ECM and ground. If greater than the specified range, repair the ground circuit for an open/high resistance.
4. Ignition ON, test for battery voltage between each voltage input circuit of the ECM and ground. If less than specified, test each voltage input circuit of the ECM for a short to ground or open/high resistance, and each voltage output circuit of the ECM for a short to ground. If the circuits test normal, replace the ECM.
5. Test for infinite resistance between DLC serial data circuit terminal 14 and ground. If less than the specified range, test both serial data circuits for a short to ground. If the circuits test normal, replace the transmission control module (TCM).
6. Test for 0 volts between DLC serial data circuit terminal 14 and ground. If greater than the specified value, test both serial data circuits for a short to voltage. If the circuits test normal, replace the TCM.
7. Ignition OFF. Test for less than 1 ohm of resistance between the DLC serial data circuit terminal 14 and the ECM serial data circuit terminal 33. If greater than the specified range, test the serial data circuit for open/high resistance. If the circuits test normal, replace the TCM.
8. Ignition OFF. Test for less than 1 ohm of resistance between the DLC serial data circuit terminal 6 and the ECM serial data circuit terminal 53. If greater than the specified range, test the serial data circuit for open/high resistance. If the circuits test normal, replace the TCM.
9. Ignition OFF, disconnect the harness connector at the TCM.
10. Test for 110-130 ohms between the DLC serial data circuit terminal 6 and terminal 14. If greater than the specified range, replace the terminator resistor. If less than the specified range, test for a short between the + and - serial data circuits. If the circuits test normal, replace the terminator resistor.
11. Connect the harness connector at the TCM.
12. Test for 115-125 ohms between the DLC serial data circuit terminal 6 and terminal 14. If less than the specified range, test for a short between the + and - serial data circuits between the TCM and ECM. If the circuits test normal, replace the TCM.
13. If the circuits test normal, replace the ECM.

Perform the Diagnostic Repair Verification after completing the repair.

1. «Control Module References»(/chevrolet/colorado/i-2004-2012/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for module replacement, setup, and programming
2. «GMLAN Wiring Repairs»(/chevrolet/colorado/i-2004-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis)

Data Link References

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

Data Link References

Removal Procedure

1. Ensure the ignition switch is in the OFF position.
2. Remove the right front hinge pillar trim panel. Refer to «Body Hinge Pillar Trim Panel Replacement - Right Side»(/chevrolet/colorado/i-2004-2012/remont/exteriorinterior-trim/#interior-trim-and-paneling) .
3. Disconnect the body wiring harness electrical connector (1) from the BCM.
4. Disconnect the I/P wiring harness electrical connector (1) from the BCM.
5. Release the fastener retaining the body wiring harness electrical connector to the BCM.
6. Remove the 2 fasteners retaining the BCM to the hinge pillar.
7. Remove the BCM from the hinge pillar by unlocking the integral tab.
8. Remove the BCM from the vehicle.

Installation Procedure

1. Position the BCM to the vehicle.
2. Attach the BCM to the hinge pillar with the integral tab.
3. Install the 2 fasteners retaining the BCM to the hinge pillar.
4. Install the fastener retaining the body wiring harness electrical connector to the BCM.
5. Connect the body wiring harness electrical connector (1) to the BCM.
6. Connect the I/P wiring harness electrical connector (1) to the BCM.
7. Install the right front hinge pillar trim panel. Refer to «Body Hinge Pillar Trim Panel Replacement - Right Side»(/chevrolet/colorado/i-2004-2012/remont/exteriorinterior-trim/#interior-trim-and-paneling) .
8. If installing a replacement BCM, program the BCM. Refer to «Control Module References»(/chevrolet/colorado/i-2004-2012/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) .

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/colorado/i-2004-2012/remont/gauges-instrument-panels/#instrument-panel-system-displays-gages__audible-warnings-description-and-operation) .
2. Automatic door locks-Refer to «Power Door Locks Description and Operation»(/chevrolet/colorado/i-2004-2012/remont/door-locks-anti-theft-systems/#door-lock-systems-door-handles) .
3. Automatic headlamp control-Refer to «Exterior Lighting Systems Description and Operation»(/chevrolet/colorado/i-2004-2012/remont/exterior-lights/#lighting-systems) .
4. Horns-Refer to «Horns System Description and Operation»(/chevrolet/colorado/i-2004-2012/remont/horns/#horn-system) .
5. Interior lighting-Refer to «Interior Lighting Systems Description and Operation»(/chevrolet/colorado/i-2004-2012/remont/exterior-lights/#lighting-systems) .
6. Keyless entry-Refer to «Keyless Entry System Description and Operation»(/chevrolet/colorado/i-2004-2012/remont/door-locks-anti-theft-systems/#keyless-entry-system-remote-functions__keyless-entry-system-description-and-operation) .
7. Passlock theft deterrent-Refer to «Immobilizer Description and Operation (North America, except Canada)»(/chevrolet/colorado/i-2004-2012/remont/door-locks-anti-theft-systems/#immobilizer-system) or «Immobilizer Description and Operation (Canada, Europe, Middle East, and Asia)»(/chevrolet/colorado/i-2004-2012/remont/door-locks-anti-theft-systems/#immobilizer-system__immobilizer-description-and-operation-canada-europe) .
8. Retained Accessory Power (RAP)-Refer to «Retained Accessory Power (RAP) Description and Operation»(/chevrolet/colorado/i-2004-2012/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-introduction) .
9. Theft deterrent-Refer to «Content Theft Deterrent (CTD) Description and Operation»(/chevrolet/colorado/i-2004-2012/remont/door-locks-anti-theft-systems/#theft-deterrent-system__content-theft-deterrent-ctd-description-and) .
10. Wipers/Washer-Refer to «Wiper/Washer System Description and Operation»(/chevrolet/colorado/i-2004-2012/remont/wiperwasher-systems/#wiper-system-washer-system) .

Power Mode

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

The data link connector (DLC) allows a scan tool to communicate with the class 2 serial data line. The serial data line is the means by which the microprocessor-controlled modules 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 diagnostic trouble codes (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.

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. Class 2 serial data at terminal 2
4. Common signal ground at terminal 5

Class 2 Serial Data Line

The class 2 serial data line on this vehicle is a combination ring-star configuration, where body control module (BCM) is connected to multiple modules. Refer to Data Communication Schematics . The following modules communicate on class 2 bus

1. The BCM
2. The communication interface module (OnStar®), w/UE1
3. The digital radio receiver (DRR), w/U2K
4. The electronic brake control module (EBCM)
5. The inflatable restraint sensing and diagnostic module (SDM)
6. The instrument panel cluster (IPC)
7. The powertrain control module (PCM)
8. The radio
9. The transfer case shift control module (TCSCM), w/4WD

See also:
• Diagnostic System Check - Vehicle
• Strategy Based Diagnosis
• Diagnostic Procedure Instructions
• Diagnostic Repair Verification
• Control Module References
• Component Connector End Views
• Circuit Testing
• Connector Repairs
• Testing for Intermittent Conditions and Poor Connections
• Wiring Repairs
• Diagnostic Trouble Code (DTC) List - Vehicle
• GMLAN Wiring Repairs
• Checking Aftermarket Accessories
• Body Hinge Pillar Trim Panel Replacement - Right Side
• Audible Warnings Description and Operation
• Power Door Locks Description and Operation
• Exterior Lighting Systems Description and Operation
• Horns System Description and Operation
• Keyless Entry System Description and Operation
• Immobilizer Description and Operation (North America, except Canada)
• Immobilizer Description and Operation (Canada, Europe, Middle East, and Asia)
• Retained Accessory Power (RAP) Description and Operation
• Content Theft Deterrent (CTD) Description and Operation
• Wiper/Washer System Description and Operation
• DTC B1000