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U2603




DTC U2603

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 U2603
- Battery Energy Control Module Lost Communication with Hybrid/EV Battery Interface Control Module 1

For symptom byte information, refer to Symptom Byte List Symptom Byte List.

Diagnostic Fault Information






Circuit/System Description

Devices connected to the serial data circuits monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the devices. The devices 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 device as an availability indication of the transmitter device. Each message contains the identification number of the transmitter device.

The scan tool does not communicate the Hybrid/EV Battery Interface Control Module 1 on Battery Energy Control Module (BECM) dedicated bus.

Conditions for Running the DTC

* The device 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/EV Battery Interface Control Module 1 to Battery Energy Control Module within 4 seconds.

Action Taken When the DTC Sets

* Cell voltage or cell temperature corresponding to Hybrid/EV Battery Interface Control Module 1 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 U2603 is a type A DTC.

Conditions for Clearing the DTC

The DTC U2603 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 device on the data communication circuit was disconnected while the communication circuit is awake.

- Power to one or more devices was interrupted during diagnosis.

- A low battery condition was present, so some devices stop communicating when battery voltage drops below a certain threshold.

- Battery power was restored to the vehicle and devices 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 device may have a U-code stored in history that does not require any repairs. Issues with late or corrupted messages between devices can be temporary with no apparent symptom or complaint; this does not mean the device is faulty. Do not replace a device based only on a history U-code.

* Do not replace a device reporting a U-code. The U-code identifies which device needs to be diagnosed for a communication issue.

* Communication may be available between the device and the scan tool with one or more GMLAN serial data systems inoperative. This condition is due to the device using multiple GMLAN busses.

* Use Data Link References Initial Inspection and Diagnostic Overview to determine what GMLAN serial data communications the non communicating device uses.

* The device 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 device.

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. Vehicle in Service Mode.

2. Verify that DTC U2401 is not set.

• If the DTC is set
Refer to DTC U2401 U2401.

• If the DTC is not set

3. Verify each scan tool Hybrid/EV Battery 1-96 parameters are between 3.0-4.1 V and within 0.1 V of each other.

• If any parameters are not within the specified range
Refer to DTC P0B3B-P0BBB, P1B16-P1B2D, P1B45-P1BFE, P1E01-P1E06, or P1E4C-P1E8A P0B3B.

• If all parameters are within the specified range

4. Refer to Circuit/System Testing.

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 includes the following steps:


* 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 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 if you have any questions.


Note: Use the schematics and connector end views to identify the device's 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, all access doors closed, all vehicle systems OFF, and all keys at least 3 meters (9.8 feet) away from vehicle. Disconnect the X1 harness connector at the K112A Hybrid/EV Battery Interface Control Module 1. It may take up to 2 minutes for all vehicle systems to power down.

4. Test for less than 10 ohms between the low reference circuit terminal 12 X1 and ground.

• If 10 ohms or greater

1. Vehicle OFF, disconnect the X2 harness connector at the K16 Battery Energy Control Module.

2. Test for less than 2 ohms in the low reference circuit end to end.

• If 2 ohms or greater, repair the open/high resistance in the circuit.

• If less than 2 ohms, replace the K16 Battery Energy Control Module.

• If less than 10 ohms

5. Vehicle in Service Mode.

6. Test for 4.8-5.2 V between the 5 V reference circuit terminal 9 X1 and ground.

• If less than 4.8 V

1. Vehicle OFF, disconnect the X2 harness connector at the K16 Battery Energy Control Module.

2. Test for infinite resistance between the 5 V reference circuit and ground.

• If less than infinite resistance, repair the short to ground on the circuit.

• If infinite resistance

3. Test for less than 2 ohms in the 5 V reference circuit end to end.

• If 2 ohms or greater, repair the open/high resistance in the circuit.

• If less than 2 ohms, replace the K16 Battery Energy Control Module.

• If greater than 5.2 V

1. Vehicle OFF, disconnect the X2 harness connector at the K16 Battery Energy Control Module, Vehicle in Service Mode.

2. Test for less than 1 V between the 5 V reference circuit and ground.

• If 1 V or greater, repair the short to voltage on the circuit.

• If less than 1 V, replace the K16 Battery Energy Control Module.

• If between 4.8-5.2 V

7. Vehicle in Service Mode.

8. Test for 4.8-5.2 V between the high voltage fault signal circuit terminal 13 X1 and ground.

• If less than 4.8 V

1. Vehicle OFF, disconnect the X2 harness connector at the K16 Battery Energy Control Module.

2. Test for infinite resistance between the high voltage fault signal circuit and ground.

• If less than infinite resistance, repair the short to ground on the circuit.

• If infinite resistance

3. Test for less than 2 ohms in the high voltage fault signal circuit end to end.

• If 2 ohms or greater, repair the open/high resistance in the circuit.

• If less than 2 ohms, replace the K16 Battery Energy Control Module.

• If greater than 5.2 V

1. Vehicle OFF, disconnect the X2 harness connector at the K16 Battery Energy Control Module, Vehicle in Service Mode.

2. Test for less than 1 V between the high voltage fault signal circuit and ground.

• If 1 V or greater, repair the short to voltage on the circuit.

• If less than 1 V, replace the K16 Battery Energy Control Module.

• If between 4.8-5.2 V

9. Vehicle OFF, all access doors closed, all vehicle systems OFF, and all keys at least 3 meters (9.8 feet) away from vehicle. Disconnect the X2 harness connector at the K16 Battery Energy Control Module. It may take up to 2 minutes for all vehicle systems to power down.

10. Test for less than 2 ohms in each serial data circuit between the K112A Hybrid/EV Battery Interface Control Module 1 and K16 Battery Energy Control Module:

* K112A Hybrid/EV Battery Interface Control Module 1 terminal 10 X1 and K16 Battery Energy Control Module terminal 12 X2

* K112A Hybrid/EV Battery Interface Control Module 1 terminal 11 X1 and K16 Battery Energy Control Module terminal 11 X2

• If 2 ohms or greater
Repair the open/high resistance in the serial data circuit.

• If less than 2 ohms

11. Replace the K112A Hybrid/EV Battery Interface Control Module 1.

Repair Instructions

Perform the Diagnostic Repair Verification Verification Tests after completing the repair.

* GMLAN Wiring Repairs GMLAN Wiring Repairs

* Control Module References Programming and Relearning for device replacement, programming and setup

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