U1888

DTC U1888

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 U1888 00
- Lost Communication with Battery Pack

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 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.

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. Only the modules using high speed GMLAN serial data are connected to the enable or wake up circuits. Refer to the schematics to determine which modules activate and are activated using the enable or wake up circuits. DTC U1888 is set by the drive motor generator battery control module, but is stored in and reported by the hybrid powertrain control modul

Conditions for Running the DTC

* The system voltage is between 9-16 volts.
* The vehicle power mode master requires serial data communication to occur fro this specific module.

Conditions for Setting the DTC

A supervised periodic message that includes the transmitter module availability has not been received.

Action Taken When the DTC Sets

* 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.
* The vehicle will not start or run because the 300 volt battery contactors are OPEN.

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.

Circuit/System Verification

With a scan tool, ensure the following DTCs are not present in the modules as follows:
BCM

U2099
PSCM

U0146
SDG module

* SDG module - U0111
* SDG module - B1453

If the DTC is set, refer to Diagnostic Trouble Code (DTC) List - Vehicle (Diagnostic Trouble Code (DTC) List - Vehicle).