Part 2
Conditions for Running the DTC
Voltage supplied to the module is in the normal operating voltage range of 9 - 16 volts.
DTCs B1327, B1328, U1300, U1301, U1305 are not set as current.
The vehicle power mode requires serial data communication to occur.
Conditions for Setting the DTC
A message containing a critical operating parameter has not been received within the last 5 seconds after establishing class 2 serial data communication.
Action Taken When the DTC Sets
The module uses a default value for the missing parameter.
Conditions for Clearing the DTC
A current DTC clears when the malfunction is no longer present.
A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.
Diagnostic Aids
When a malfunction such as an open fuse to a module occurs while modules are communicating, a DTC U1001-1254 Loss of XXX Communications is set current. When the modules stop communicating the current DTC U1001-1254 Loss of XXX Communications 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 is set current by the other modules. If the malfunction occurs when the modules are not communicating, only U1000 or U1255 is set.
Test Description
DTC U1001 and U1254
Circuit/System 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 monitoring. A critical operating parameter is one which, when not received, requires that the module use a default value for that parameter. Once an identification number is learned by a module, it will monitor for that module's Node Alive message. Each module on the class 2 serial data circuit which is powered and performing functions that require detection of a communications malfunction is required to send a Node Alive message every 2 seconds. When no message is detected from a learned identification number for 5 seconds, a DTC U1XXX where XXX is equal to the 3-digit identification number is set.
The control module ID number list above provides a method for determining which module is not communicating. A module with a class 2 serial data circuit malfunction or which loses power during the current ignition cycle will have a Loss of Communication DTC set by other modules that depend on information from that failed module. The modules that can communicate will set a DTC indicating the module that cannot communicate.
Diagnostic Order
When more than one Loss of Communication DTC is set in either one module or in several modules, diagnose the DTCs in the following order:
1. Current DTCs before history DTCs unless told otherwise in the diagnostic table.
2. The DTC which is reported the most times.
3. From the lowest number DTC to the highest number DTC.
Conditions for Running the DTC
The following DTCs do not have a current status:
^ B1327
^ B1328
^ U1300
^ U1301
^ U1305
AND
^ The vehicle power mode requires serial data communication to occur.
Conditions for Setting the DTC
A node alive message has not been received from a module with a learned identification number within the last 5 seconds.
Action Taken When the DTC Sets
The module uses a default value for the missing parameter.
Conditions for Clearing the DTC
A current DTC clears when the malfunction is no longer present.
A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.
Diagnostic Aids
When multiple Loss of Communication DTCs are set concurrently, the cause is likely to be 2 opens in the ring portion of the class 2 serial data circuit. Use the Control Modules and Devices ‐ Description and Identification Number table in order to determine which modules are not communicating. Use the class 2 serial data circuit schematic in order to determine the location of the opens.
Test Description
The number above refers to the step number on the diagnostic table.
DTC U0073 or U2100
DTC Descriptors
DTC U0073 00: Control Module Communication Bus Off
DTC U0073 71: ECU HS Bus Off
DTC U0073 72: ECU LS Bus Off
DTC U2100 00: Controller Area Network (CAN) Bus Communication
DTC U2100 47: Controller Area Network (CAN) Bus Communication
Circuit/System Description
The serial data circuits are serial data buses used to communicate information between the control modules. The serial data circuits also connect directly to the data link connector (DLC).
Conditions for Running the DTCs
Supply voltage at the modules are in the normal operating range.
The vehicle power mode requires serial data communications.
Conditions for Setting the DTC
The module setting the DTC has attempted to establish communications on the serial data circuits more than 3 times.
Action Taken When the DTCs Sets
The module suspends all message transmission.
The module uses default values for all parameters received on the serial data circuits.
The module inhibits the setting of all other communication DTCs.
Conditions for Clearing the DTC
A current DTC clears when the malfunction is no longer present.
A history DTC clears when the module ignition cycle counter reaches the reset threshold of 50, without a repeat of the malfunction.
Circuit/System Verification
Refer to Data Link References to determine which serial data system is used for a specific module.
This DTC cannot be retrieved with a current status. Diagnosis is accomplished using the following symptom procedures:
Scan Tool Does Not Communicate with High Speed GMLAN Device in SI.
OR
Scan Tool Does Not Communicate with Low Speed GMLAN Device in SI.
DTC U0140 - U0184
Circuit Description
Modules connected to the GMLAN 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 GMLAN serial data circuit. When the module detects one of the following conditions on the GMLAN serial data circuit, a DTC will set.
Operating information and commands are exchanged among the modules. In addition to this, Node Alive messages are transmitted by each module on the GMLAN serial data circuit.
Conditions for Setting the DTCs
Diagnostic algorithms are designed so that a single point failure within a particular node shall result in a single DTC/FTB combination being set. Any recognized faults shall generate one DTC. Recognized faults may include but are not limited to the following:
^ Open or shorted condition on an I/O Circuit outside of normal operation of that circuit.
^ Erratic signal of a circuit, outside of normal operation, which can be readily and repeatedly recognized as erratic.
^ A condition, outside of normal operation, which causes a customer perception of a performance problem.
^ A condition whether hardware or data link error, which causes a device to operate in a default or fail soft mode.
^ A condition which changes or limits system performance.
^ Network supervision/signal supervision errors.
^ ECU Internal errors.
^ Criteria determined by legislation.
An initialization or shutdown self-test shall be performed and may include but is not limited to the following:
^ RAM check
^ ROM/EEPROM/Flash check
^ I/O check
Any faults detected during the initialization self-test shall generate a DTC. All nodes also continuously perform a self-test while in an active state.
DTCs and their associated telltales will set as a result of unprogrammed or unlearned information.
DTCs, which are defined for system configuration (e.g. Vehicle Option Content not programmed) do not support the history status bit (set =0). Warning indicator bit is also set, when applicable, while this DTC is present.
Action Taken When the DTCs Sets
The module suspends all message transmission.
The module uses default values for all parameters received on the serial data circuits.
The module inhibits the setting of all other communication DTCs.
Conditions for Clearing the DTC
A current DTC clears when the malfunction is no longer present.
A history DTC clears when the module ignition cycle counter reaches the reset threshold of 50, without a repeat of the malfunction.
Circuit/System Verification
Refer to Data Link References to determine which serial data system is used for a specific module.
The DTCs cannot be retrieved with a current status. Diagnosis is accomplished using the following symptom procedures:
Scan Tool Does Not Communicate with High Speed GMLAN Device in SI.
OR
Scan Tool Does Not Communicate with Low Speed GMLAN Device in SI.
DTC U1300, U1301, or U1305
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. 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.
Conditions for Running the DTCs
Voltage supplied to the module is in the normal operating voltage range.
The vehicle power mode requires serial data communication to occur.
Conditions for Setting the DTCs
No valid messages are detected on the Class 2 serial data circuit.
The voltage level detected on the Class 2 serial data circuit is in one of the following conditions:
High
OR
Low
The above conditions are met for more than 3 seconds.
Circuit/System Verification
These DTCs cannot be retrieved with a current status. To diagnose use the Scan Tool Does Not Communicate with a Class 2 Device. Refer to SI.
An intermittent condition is likely to be caused by a short on the Class 2 serial data circuit. To diagnose use the Scan Tool Does Not Communicate with a Class 2 Device. Refer to SI.
DTC B2455
DTC Descriptors
DTC B2455 01: Cellular Phone Microphone Circuit Short to Battery
DTC B2455 02: Cellular Phone Microphone Circuit Short to Ground
DTC B2455 04: Cellular Phone Microphone Circuit Open Circuit
Circuit/System Description
Without RPO UAV
The vehicle communication interface module (VCIM) uses the cellular phone microphone to allow driver communication with OnStar(R).
With RPO UAV
The vehicle communication interface module (VCIM) and navigation radio use the cellular phone microphone to allow driver communication with OnStar(R), as well as to operate the voice recognition/voice guidance feature of the navigation radio.
Conditions for Running the DTC
The ignition is in RUN or ACC position.
System voltage is between 9.5 - 15.5 volts.
The above conditions are met for more than 10 seconds.
Conditions for Setting the DTC
B2455 01: A short to battery is detected on the cellular microphone signal circuit.
B2455 02: A short to ground is detected on the cellular microphone signal circuit.
B2455 04: An open circuit is detected on the cellular microphone signal circuit.
Action Taken When the DTC Sets
The VCIM and/or navigation radio (RPO UAV) will not receive any signal from the microphone.
The OnStar(R) status LED turns red.
Voice recognition will not function.
Conditions for Clearing the DTC
A current DTC clears when the condition for setting the DTC is no longer present.
A history DTC clears after 50 malfunction-free ignition cycles.
Circuit/System Testing
Without RPO UAV
1. Turn OFF the ignition and all electrical components, including the scan tool.
2. Disconnect the harness connector at the cellular microphone.
3. Test for less than 5 Ohms between the low reference circuit terminal A and ground.
^ If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the VCIM.
4. Ignition ON, test for 9 - 11 volts between the signal circuit terminal B and ground.
^ If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the VCIM.
^ If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the VCIM. Refer to the appropriate vehicle in SI.
5. If all circuits test normal, test or replace the cellular microphone.
Circuit/System Testing
With RPO UAV
1. Turn OFF the ignition and all electrical components, including the scan tool.
2. Disconnect the X4 harness connector at the navigation radio and the harness connector at the cellular microphone.
3. Test for less than 5 Ohms between the low reference circuit terminal A and ground.
^ If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the VCIM. Refer to the appropriate vehicle in SI.
4. Ignition ON, test for 9 - 11 volts between the signal circuit terminal B and ground.
^ If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the VCIM.
^ If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the VCIM.
5. If all circuits test normal, test or replace the cellular microphone.
6. Connect the X4 harness connector at the navigation radio.
7. With a scan tool, verify that DTC B2455 is not set as current in the navigation radio.
^ If DTC B2455 is set as current, replace the navigation radio. Refer to the appropriate vehicle in SI.
DTC B2462, B2483, or B2484
Circuit/System Description
The vehicle communication interface module (VCIM) receives information from a specific navigation antenna located on the outside of the vehicle. The navigation antenna is connected to the VCIM via a shielded coaxial cable. The antenna cable also provides a path for DC current for powering the antenna.
DTC Descriptors
DTC B2462 02: Global Positioning System (GPS) Antenna Malfunction Short to Ground
DTC B2462 04: Global Positioning System (GPS) Antenna Malfunction Open Circuit
DTC B2483: Global Positioning System (GPS) Antenna Malfunction Short to Ground
DTC B2484: Global Positioning System (GPS) Antenna Malfunction Open Circuit
Conditions for Running the DTCs
The ignition is in RUN or ACC position
System voltage is between 9.5 - 15.5 volts.
The above conditions are met for more than 1 second.
Conditions for Setting the DTCs
B2462 02: The CIM detects a short to ground on the navigation antenna signal circuit.
B2462 04: The CIM detects an open/high resistance on the navigation antenna signal circuit.
B2483: The CIM detects a short to ground on the navigation antenna signal circuit.
B2484: The CIM detects an open/high resistance on the navigation antenna signal circuit.
Action Taken When the DTCs Set
The OnStar(R) status LED turns red.
The OnStar(R) Call Center cannot locate the vehicle.
Conditions for Clearing the DTCs
The condition responsible for setting the DTC no longer exists.
A history DTC will clear once 50 consecutive malfunction-free ignition cycles have occurred.
Circuit/System Testing
Turn OFF the ignition.
1. Disconnect the navigation antenna coax cable from the VCIM.
2. Ignition ON, test for 4.5-5.5 volts between the VCIM coax cable center conductor terminal at the VCIM and ground.
^ If not within the specified range, replace the VCIM. Refer to the appropriate vehicle in SI.
3. Reconnect the coax cable to the VCIM.
4. Disconnect the coax cable from the navigation antenna.
5. Test for 4.55.5 volts between the coax cable center conductor and the outer shield.
^ If not within the specified range, replace the coax cable.
6. If all circuits test normal, replace the navigation antenna. Refer to the appropriate vehicle in SI.
DTC B2470
DTC Descriptor
DTC B2470 04: Cellular Phone Antenna Circuit Malfunction Open Circuit
Circuit/System Description
The cellular antenna is connected to the vehicle communication interface module (VCIM) with an RG-58 coax cable. The VCIM collects the data from the cellular antenna once every second.
Conditions for Running the DTC
Ignition is in RUN or ACC position
System voltage is between 9.5 - 15.5 volts.
The above conditions are met for more than 1 second.
Conditions for Setting the DTC
The VCIM does not detect the presence of a cellular antenna for more than 1 second.
Action Taken When the DTC Sets
The vehicle is unable to connect to the OnStar(R) Call Center.
The OnStar(R) status LED turns red.
Conditions for Clearing the DTC
The VCIM detects the presence of a cellular antenna.
A history DTC clears after 50 malfunction-free ignition cycles.
Circuit/System Testing
Perform a visual inspection as shown above in order to verify that the cellular antenna and the cellular antenna coupling assembly are not damaged. If any components are damaged replace the assembly.
DTC B2476 or B2482
DTC Descriptors
DTC B2476 04: Cellular Phone Select Service Switch Open Circuit
DTC B2476 59: Cellular Phone Select Service Switch Stuck Button
DTC B2482 00: Cellular Phone Select Service Switch Range/Performance
Circuit Short to Ground Open / High Resistance Short to Voltage Signal Performance
Circuit/System Description
The OnStar(R) button assembly consists of 3 buttons, Call/Answer, OnStar(R) Call Center, and OnStar(R) Emergency.
The vehicle communication interface module (VCIM) supplies the OnStar(R) button assembly with 10 volts via the keypad supply voltage circuit. Each of the buttons, when pressed, completes the circuit across a resistor allowing a specific voltage to be returned to the VCIM over the keypad signal circuit. Depending upon the voltage range returned, the VCIM is able to identify which button has been activated.
Conditions for Running the DTCs
The ignition is ON.
System voltage is between 9 - 16 volts.
Conditions for Setting the DTCs
B2476 04: The VCIM detects an open/high resistance on the keypad supply voltage circuit.
B2482 and B2476 59: The VCIM detects a valid signal on the keypad signal circuit for more than 15 seconds. If one of the OnStar(R) buttons is held or stuck for 15 seconds or more, the VCIM will set these DTCs.
Action Taken When the DTCs Set
The OnStar(R) status LED turns red.
No calls can be placed.
The VCIM will ignore all inputs from the OnStar� button assembly.
Conditions for Clearing the DTCs
The condition responsible for setting the DTC no longer exists.
A history DTC will clear once 100 consecutive malfunction-free ignition cycles have occurred.
Circuit/System Testing
Component Testing