DTC U2401
Diagnostic Instructions
DTC Descriptor
DTC U2401 00: Battery Energy Control Module Dedicated Bus 1 Off
Diagnostic Fault Information
Circuit
| Short to Ground
| Open/High Resistance
| Short to Voltage
| Signal Performance
|
BECM Dedicated Serial Data (+)
| U2401
| U2401, U2603-U2606
| U2401
| -
|
BECM Dedicated Serial Data (-)
| U2401
| U2401, U2603-U2606
| U2401
| --
|
Circuit/System Description
The battery energy control module (BECM) dedicated bus is a communication bus used to communicate between the BECM and the hybrid battery interface control modules inside the hybrid battery pack assembly. The BECM dedicated bus does not communicate with the scan tool.
This diagnostic is used to check the internal BECM dedicated bus off. If the transmit error counter of a bus is greater than 255 (carry condition in case of an 8-bit transmit error counter) then the supervisor requests the physical layer to set the bus into the "Bus Off" state. At this time, the battery energy control module increases its fail count. When this fail count is over X Cal Value (7) during Y Cal Value (10 samples), this fail code will happen.
Conditions for Running the DTC
| • | The system voltage is at least 9 V. |
Conditions for Setting the DTC
The control module setting the DTC has received too many transmit errors on the BECM dedicated serial data circuits.
Action Taken When the DTC Sets
| • | DTC U2401 is a type A DTC. |
| • | The battery energy control module sends all hybrid battery interface control module data to Invalid, 0 V, and -40°C (-40°F) on high-voltage energy high-speed GMLAN bus. |
Conditions for Clearing the DTC
| • | DTC U2401 is a type A DTC. |
Diagnostic Aids
| • | Sometimes, while diagnosing a specific customer concern or after a repair, you may notice a history U-code present. However, there is no associated "current" or "active" status. Loss-of- communication U-codes such as these can set for a variety of reasons. Many times, they are transparent to the vehicle operator and technician, and/or have no associated symptoms. Eventually, they will erase themselves automatically after a number of fault-free ignition cycles. This condition would most likely be attributed to one of these scenarios: |
| - | A control module on the data communication circuit was disconnected while the communication circuit is awake. |
| - | Power to one or more control modules was interrupted during diagnosis. |
| - | A low battery condition was present, so some control modules stop communicating when battery voltage drops below a certain threshold. |
| - | Battery power was restored to the vehicle and control modules on the communication circuit did not all re-initialise at the same time. |
| - | If a loss-of-communication U-code appears in history for no apparent reason, it is most likely associated with one of the scenarios above. These are all temporary conditions and should never be interpreted as an intermittent fault, causing you to replace a part. |
| • | Do not replace a control module reporting a U-code. The U-code identifies which control module needs to be diagnosed for a communication issue. |
| • | The engine will not start when there is a total malfunction of the BECM dedicated bus. |
| • | Technicians may find various Local Area Network (LAN) communication Diagnostic Trouble Codes (DTC) with the scan tool. |
Reference Information
Schematic Reference
Connector End View Reference
Component Connector End Views
Description and Operation
Data Link Communications Description and Operation
Electrical Information Reference
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Verification
Verify that DTC U2401 is not set.
| ⇒ | If the DTC is set, replace the A4 hybrid/EV battery pack. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| ©© Copyright Chevrolet. All rights reserved |
