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DTC U2605

Diagnostic Instructions

    • Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
    • Review Strategy Based Diagnosis for an overview of the diagnostic approach.
    • Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptor

DTC U2605 00: Battery Energy Control Module Lost Communication with Hybrid/EV Battery Interface Control Module 3

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

5 V Reference

U2605

U2605

--

--

High-Voltage Fault Signal

U2605

U2605

--

--

BECM Dedicated Serial Data (+)

U2401

U2401, U2605

U2401

-

BECM Dedicated Serial Data (-)

U2401

U2401, U2605

U2401

-

Low Reference

-

U2605

--

--

Circuit/System Description

Control modules connected to the serial data circuits monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the control modules. The control 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 also, some 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.

Scan tool does not communicate the hybrid battery interface control module 3 on battery energy control module dedicated bus.

Conditions for Running the DTC

    • The control module is awake and communicating.
    • The system voltage is at least 9 V.

Conditions for Setting the DTC

There is no temperature report message from hybrid battery interface control module 3 to battery energy control module within 4 seconds.

Action Taken When the DTC Sets

    • Cell voltage or cell temperature corresponding to hybrid battery interface control module 3 will be reported by the battery energy control module to the hybrid powertrain control module 2 as 0 V or -40°C (-40°F).
    • The DTC U2605 is a type A DTC.

Conditions for Clearing the DTC

The DTC U2605 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.
    • A control module may have a U-code stored in history that does not require any repairs. Issues with late or corrupted messages between control modules can be temporary with no apparent symptom or complaint; this does not mean the control module is faulty. Do not replace a control module based only on a history U-code.
    • 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.
    • Communication may be available between the control module and the scan tool with one or more GMLAN serial data systems inoperative. This condition is due to the control module using multiple GMLAN busses.
    • Use Data Link References to determine what GMLAN serial data communications the non communicating control module uses.
    • The control module may not have internal protection for specific control circuits and may open a B+ or ignition fuse. If a fuse is open and the B+ or ignition circuit is not shorted to earth, ensure none of the control circuits are shorted to earth before replacing the non communicating control module.

Reference Information

Schematic Reference

    •  Data Communication Schematics
    •  Hybrid Energy Storage Schematics
    •  Control Module References

Connector End View Reference

Component Connector End Views

Description and Operation

Data Link Communications Description and Operation

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

  1. Vehicle in Service Mode, observe the scan tool Hybrid/EV Battery 1-96 parameters. Verify that each reading is between 3.0-4.1 V, and all readings are within 0.1 V of each other.
  2. If any of the scan tool Hybrid/EV Battery 1-96 parameters are not within the specified range, refer to DTC P0B3B-P0BBB, P1B16-P1B2D, P1B45-P1BFE, P1E01-P1E06, or P1E4C-P1E8A .
  3. Verify that DTC U2605 is not set.
  4. If the DTC is set, replace the A4 hybrid/EV battery pack.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Drive Motor Battery Replacement and Shipping Preparation
    • Control Module References for control module replacement, programming and setup
   


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