U1862
DTC U1862
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 U1862 00
- Battery Energy Control Module Lost Communication with Serial Data Gateway Module
Diagnostic Fault Information
Circuit/System Description
Modules connected to the high and low speed GMLAN serial data circuits monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules. The 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 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.
The enable signal circuit is energized by the body control module (BCM) to activate multiple modules when the BCM determines that communication is required. Some modules may still become active due to their own ignition voltage source if the enable circuit is not functional. The serial data gateway (SDG) module translates serial data messages between the high speed GMLAN serial data bus, the low speed GMLAN serial data bus, and the high speed hybrid GMLAN serial data bus. Messages between the drive motor generator battery control module and the other hybrid system control modules must pass thru the SDG module. DTC U1862 is set by the drive motor generator battery control module, but is stored in and reported by the hybrid powertrain control module (HPCM).
Conditions for Running the DTC
* The system voltage is between 9-16 volts.
* The vehicle power mode master requires serial data communication to occur from the drive motor generator battery control module via the SDG module.
Conditions for Setting the DTC
A supervised periodic message that includes the SDG module availability has not been received by the drive motor generator battery control module.
Action Taken When the DTC Sets
* The charging system will not operate properly and the vehicle battery will discharge as the vehicle is driven.
* The driver information center (DIC) displays the message Service Hybrid System.
* Multiple DTCs may set depending on the fault location and when the fault occurred.
Conditions for Clearing the DTC
* A current DTC clears when the malfunction is no longer present.
* A history DTC clears when the module ignition cycle counter reaches the reset threshold of 50, without a repeat of the malfunction.
Diagnostic Aids
* If the SDG module becomes inoperative, the drive motor generator battery control module will set DTC U1862 and other modules will set loss of communication DTCs against the SDG module.
* If serial data is lost between the SDG module and the drive motor generator battery control module multiple modules will set loss of communication DTCs against the drive motor generator battery control module.
Reference Information
Schematic Reference
* Data Communication Schematics Electrical Diagrams
* Hybrid Energy Storage Schematics
Connector End View Reference
Component Connector End Views Connector End Views By Name
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
Circuit/System Testing
1. Ignition OFF, disconnect the harness connector X2 at the SDG module.
Important: The scan tool must be disconnected and the ignition switch OFF for 30 seconds for proper test results.
2. Ignition OFF and the scan tool disconnected, open and close the driver door, and wait 1 minute.
3. Test for less than 5.0 ohms between the ground circuit terminal 18 X2 and ground.
• If greater than the specified range, test the circuit for an open/high resistance.
4. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal 8 X2 and ground.
• If the test lamp does not illuminate, test the circuit for a short to ground or an open/high resistance.
5. Test for 10.5-12.5 volts between the serial data communication enable circuit terminal 16 X2 and ground.
• If less than the specified range, test the circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the applicable communication/control module.
6. Ignition OFF, connect the harness connector X2 to the SDG module.
7. Ignition OFF, disconnect the harness connector X1 at the SDG module.
8. Ignition ON, test for 2.1-2.5 volts between the high speed GMLAN serial data bus low circuit terminal listed below and ground:
* Terminal 15 X1
* Terminal 16 X1
• If greater than the specified range, test the circuit for a short to voltage. If the circuit tests normal, replace the applicable communication/control module.
• If less than the specified range, test the circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the applicable communication/control module.
9. If all circuits test normal, replace the SDG module.
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 Relearningfor module replacement, setup, and programming