2010 Cadillac Truck Escalade RWD V8-6.2L Page 2851
DTC U1813
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Diagnostic System
Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Strategy Based Diagnosis) for an
overview of the diagnostic approach.
* Diagnostic Procedure Instructions (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Diagnostic Procedure
Instructions) provides an overview of each diagnostic category.
DTC Descriptors
DTC U1813 00
- Battery Energy Control Module Bus B High Speed Communication Enable Circuit High
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 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. The wake up circuit sends a voltage from the SDG module to the drive motor
generator battery control module to initiate certain module functions. DTC U1813 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 9-18 volts.
* Ignition is OFF.
Conditions for Setting the DTC
The drive motor generator battery control module receives voltage on wake up signal circuit for greater than 3 seconds when the ignition is OFF.
Action Taken When the DTC Sets
The hybrid system signals the engine control module (ECM) to request illumination of the malfunction indicator lamp (MIL).
Conditions for Clearing the DTC
* A current DTC clears when the malfunction is no longer present, including a key ON condition when both wake up signals are energized.
* A history DTC clears when the module ignition cycle counter reaches the reset threshold of 50, without a repeat of the malfunction.
Diagnostic Aids
DTC U1813 will always set with SDG module DTC B137A 01.
Reference Information
Schematic Reference
* Data Communication Schematics (See: Powertrain Management/Computers and Control Systems/Information Bus/Diagrams/Electrical
Diagrams)
* Hybrid Controls Schematics ()
Connector End View Reference
