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U2605




DTC U2605

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions 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/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-initialize 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 Initial Inspection and Diagnostic Overview 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 ground, ensure none of the control circuits are shorted to ground before replacing the non communicating control module.

Reference Information
Schematic Reference

* Data Communication Schematics [1][2]Electrical Diagrams
* Hybrid Energy Storage Schematics Hybrid Energy Storage Schematics
* Control Module References Programming and Relearning

Connector End View Reference

Component Connector End Views Hybrid/EV Battery Pack X1
Description and Operation

Data Link Communications Description and Operation Description and Operation
Electrical Information Reference

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

Scan Tool Reference

Control Module References Programming and Relearning for scan tool information
Special Tools

EL-48900 - HEV Safety Kit

For equivalent regional tools, refer to Special Tools Tools and Equipment.

Circuit/System Verification

1. Verify that DTC U2401 is not set.

• If the DTC is set, refer to DTC U2401 U2401.

2. Verify that DTC U2603 or U2604 is not set.

• If any of the DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle Diagnostic Trouble Code (DTC) List - Vehicle.

3. 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.

• 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 P0B3B.

Circuit/System Testing

Danger: Always perform the High Voltage Disabling procedure prior to servicing any High Voltage component or connection. Personal Protection Equipment (PPE) and proper procedures must be followed.


The High Voltage Disabling procedure will perform the following tasks:


* Identify how to disable high voltage.

* Identify how to test for the presence of high voltage.

* Identify condition under which high voltage is always present and personal protection equipment (PPE) and proper procedures must be followed.


Before working on any high voltage system, be sure to wear the following Personal Protection Equipment:


* Safety glasses with appropriate side shields when within 15 meters (50 feet) of the vehicle, either indoors or outdoors.

* Certified and up-to-date Class "0" Insulation gloves rated at 1000V with leather protectors.


- Visually and functionally inspect the gloves before use.

- Wear the Insulation gloves with leather protectors at all times when working with the high voltage battery assembly, whether the system is energized or not.


Failure to follow the procedures exactly as written may result in serious injury or death.


Danger: The Volt Battery Pack will utilize an exchange program. Please consult the most recent revision of bulletin/PI #PIP4841, available in Service Information (SI), for a list of approved Volt Battery Pack service procedures. Components that may be removed and serviced without exchanging the complete battery pack are identified in the bulletin/PI. Please contact the GM Technical Assistance Center (1-877-446-8227) if you have any questions.


Note: Use the schematic to identify the following:

* The control module locations on the battery energy control module dedicated serial data circuits
* The control module 5 V reference, high voltage fault signal, low reference, and serial data circuit terminals

1. Perform the High Voltage Disabling procedure before proceeding with this diagnostic. Refer to High Voltage Disabling High Voltage Disabling.
2. Reconnect the 12 V battery.
3. Vehicle OFF, disconnect the X1 harness connector at the K112C hybrid battery interface control module 3.
4. Vehicle OFF and all vehicle systems OFF, all keys at least 3 meters away from vehicle, all access doors closed. It may take up to 2 minutes for all vehicle systems to power down. Test for less than 10 ohm between the low reference circuit terminal 12 X1 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 K112B hybrid battery interface control module 2.

5. Vehicle in Service Mode, test for 4.8-5.2 V between the 5 V reference circuit terminal 9 X1 and ground.

• If less than the specified range, test the 5 V reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K112B hybrid battery interface control module 2.
• If greater than the specified range, test the 5 V reference circuit for a short to voltage. If the circuit tests normal, replace the K112B hybrid battery interface control module 2.

6. Vehicle in Service Mode, test for 4.8-5.2 V between the high voltage fault signal circuit terminal 13 X1 and ground.

• If less than the specified range, test the high voltage fault signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K112B hybrid battery interface control module 2.
• If greater than the specified range, test the high voltage fault signal circuit for a short to voltage. If the circuit tests normal, replace the K112B hybrid battery interface control module 2.

7. Vehicle OFF, disconnect the X1 harness connector at the K112B hybrid battery interface control module 2.
8. Vehicle OFF and all vehicle systems OFF, all keys at least 3 meters away from vehicle, all access doors closed. It may take up to 2 minutes for all vehicle systems to power down. Test for less than 2 ohm in each serial data circuit between the K112C hybrid battery interface control module 3 and K112B hybrid battery interface control module 2.

* K112C hybrid battery interface control module 3 serial data circuit terminal 10 X1 and K112B hybrid battery interface control module 2 serial data circuit terminal 17 X1
* K112C hybrid battery interface control module 3 serial data circuit terminal 11 X1 and K112B hybrid battery interface control module 2 serial data circuit terminal 16 X1

• If greater than the specified range, test the serial data circuit for an open/high resistance between the K112C hybrid battery interface control module 3 and the K112B hybrid battery interface control module 2.

Note: The K112C hybrid battery interface control module 3 has a loop in the harness that connects its 5 V reference circuit terminal 21 X1 to its signal ground circuit terminal 20 X1. Test this circuit for the appropriate failure mode short to voltage, short to ground, or open/high resistance prior to replacing the K112C hybrid battery interface control module 3.

9. If all circuits test normal, replace the K112C hybrid battery interface control module 3.

Repair Instructions

Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.

* GMLAN Wiring Repairs GMLAN Wiring Repairs
* Control Module References Programming and Relearning for control module replacement, programming and setup

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