A friend got this code today U0101. There is another diagnostic for it under the BCM diagnostics. The one I posted above was under the PCM diagnostics. Unless you have have alfaOBD, you can't be sure which diagnostic to use, U0101-00 or U-0101-87.
Here is the other:
28 - DTC-Based Diagnostics / MODULE, Body Control (BCM) / Diagnosis and Testing
U0101-87-LOST COMMUNICATION WITH TCM - MISSING MESSAGE
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Theory of Operation
The primary communication network between electronic control modules is the Controller Area Network (CAN) data bus system. The Controller Area Network (CAN) data bus allows all electronic modules connected to the bus to share information with each other. Regardless of whether a message originates from a module on the higher speed CAN C (500K) Bus or on the lower speed bus, CAN Interior High Speed (IHS) (125K) Bus, the message structure and layout is similar, which allows the Body Control Module (BCM) to process and transfer messages between the CAN buses. The BCM stores Diagnostic Trouble Codes (DTCs) for certain bus network faults on the CAN C (500K) Bus and CAN IHS (125K) Bus.
The CAN bus modules are connected in parallel to the two-wire bus using a twisted pair, where the wires are wrapped around each other to provide shielding from unwanted electromagnetic induction, thus preventing interference with the relatively low voltage signals being carried through them. While the CAN bus is operating (active), one of the bus wires will carry a higher voltage and is referred to as the CAN High or CAN bus (+) wire, while the other bus wire will carry a lower voltage and is referred to as the CAN Low or CAN bus (-) wire.
For additional information on the communication network and star connector locations, (Refer to 08 - Electrical/8E - Electronic Control Modules/COMMUNICATION - Description) .
•When Monitored:
With the ignition on for at least five seconds.
Battery voltage between 10 and 16 volts.
Body Control Module (BCM) is configured correctly.
•Set Condition:
Bus messages not received from the Transmission Control Module (TCM) for approximately two to five seconds.
Possible Causes
CAN C BUS (+) CIRCUIT SHORTED TO VOLTAGE
CAN C BUS (-) CIRCUIT SHORTED TO GROUND
DTCS RELATED TO BATTERY VOLTAGE, IGNITION, OR VIN MESSAGES
BCM NOT CONFIGURED CORRECTLY
TCM POWER AND GROUND
TRANSMISSION CONTROL MODULE (TCM)
MODULE THAT SET THIS DTC
1.VERIFY DTC IS ACTIVE
NOTE: Make sure the battery voltage is between 10 and 16 volts before proceeding.
1. With the scan tool, read active DTCs.
Is this DTC active?
Yes
•Go To 2
No
•(Refer to 29 - Non-DTC Diagnostics/Communication - Diagnosis and Testing) and perform the Stored Lost Communication DTCs diagnostic procedure.
2.CHECK FOR ANY OF THE FOLLOWING ACTIVE DTCS
1. With the scan tool, read all active DTCs from all modules.
NOTE: Check for BCM configuration, CAN C hardware electrical, VIN Missing/Mismatch, battery or ignition related DTCs.
Does the scan tool display any active DTCs to the conditions listed above?
Yes
•Go to and perform the appropriate diagnostic procedure.
No
•Go To 3
3.VERIFY THE TCM IS ACTIVE ON THE BUS
1. Turn the ignition on.
2. With the scan tool, verify the TCM is active on the bus.
Is the TCM active on the bus?
Yes
•Go To 4
No
•(Refer to 29 - Non-DTC Diagnostics/Communication - Diagnosis and Testing) and perform the NO RESPONSE FROM TCM diagnostic procedure.
4.CHECK FOR ADDITIONAL COMMUNICATION RELATED DTCS
1. With the scan tool, read all the DTCs.
Is there more than one module with active DTCs “Logged Against” the TCM?
Yes
•Replace/update the TCM in accordance with the Service Information. ) .
•Perform the TRANSMISSION VERIFICATION TEST. Refer to 28 - DTC-Based Diagnostics/MODULE, Transmission Control (TCM) /Standard Procedure
No
•Go To 5
5.CLEAR DTC IN MODULE SETTING FAULT
1. With the scan tool, select the module setting the DTC against the TCM.
2. Clear active DTCs.
Is this DTC still active?
Yes
•Replace/update the module that set this DTC in accordance with the Service Information.
•Perform the appropriate verification test for the module being replaced. If there is no verification test for the associated module perform the BODY VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Body Control (BCM) - Standard Procedure).
No
•Go To 6
6.CYCLE IGNITION
1. Cycle the ignition from RUN to OFF three times ending with the key in the RUN position.
Does this DTC become active?
Yes
•Go To 7
No
•The condition is not present at this time. Using the wiring diagram/schematic as a guide, inspect the wiring for chafed, pierced, pinched, and partially broken wires and the wiring harness connectors for broken, bent, pushed out, and corroded terminals.
•Perform the appropriate verification test for the module. If there is no verification test for the associated module perform the BODY VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Body Control (BCM) - Standard Procedure).
7.CHECK FOR ADDITIONAL LOST COMMUNICATION FAULTS
1. With the scan tool, view the modules.
Does the BCM and other CAN C BUS modules show Lost Communication with the remaining CAN C BUS modules?
Yes
•Go To 8
No
•Replace/update the module that set this DTC in accordance with the Service Information.
•Perform the appropriate verification test for the module being replaced. If there is no verification test for the associated module perform the BODY VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Body Control (BCM) - Standard Procedure).
8.CHECK THE CAN C BUS (+) CIRCUIT FOR A SHORT TO VOLTAGE
1. Measure the voltage between the (D57) CAN C Bus (+) circuit and ground.
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Is the voltage above 5.0 volts?
Yes
•Repair the short to voltage in the CAN C Bus (+) circuit. The short to voltage is present in one of the CAN C Bus circuits. Use the Star Connectors to isolate portions of the CAN C Bus in order to locate the concern.
•Perform the BODY VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Body Control (BCM) - Standard Procedure).
No
•Go To 9
9.CHECK THE CAN C BUS (-) CIRCUIT FOR A SHORT TO GROUND
1. Turn the ignition off.
2. Measure the resistance between ground and the (D58) CAN C Bus (-) circuit.
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Is the resistance below 10k Ohms?
Yes
•Repair the short to ground in the CAN C Bus (-) circuit. The short to ground is present in one of the CAN C Bus circuits. Use the Star Connectors to isolate portions of the CAN C Bus in order to locate the concern.
•Perform the BODY VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Body Control (BCM) - Standard Procedure).
No
•Replace/update the module that set this DTC in accordance with the Service Information.
•Perform the appropriate verification test for the module being replaced. If there is no verification test for the associated module perform the BODY VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Body Control (BCM) - Standard Procedure).
