Diagnostic Instructions
| • | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
| • | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
| • | 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 HighDiagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
Wake Up Signal (circuit 968) | B137A* in SDGM | U1812** | U1813*** | -- |
* Other modules will set other DTC with this fault. ** Open at SDGM or BECM will set DTC U1812 in HPCM. Open at PIM will set DTC U189A in the HPCM. *** Will set DTC U1813, U1875, U1876, U1878, U1879 as current in the HPCM with the key OFF, and as history with the key ON. Will also likely cause a parasitic drain on battery. | ||||
Circuit/System Description
Modules connected to the LAN 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.
A wake up signal circuit (968) is energized by the serial data gateway module (SDGM) to activate the hybrid powertrain control module (HPCM) which is part of the drive motor generator power inverter module (PIM) and the drive motor generator battery control module (BECM) when serial data is required. The SDGM determines that serial data is required when a wake up signal (circuit 5986) is received from the body control module (BCM). The wake up signal (circuit 5986) from the BCM is also connected to the BECM, and the BECM compares the status of both circuits.
Conditions for Running the DTC
| • | The system voltage is between 9-18 volts. |
| • | Ignition key OFF. |
Conditions for Setting the DTC
The BECM receives voltage from the SDGM on wake up signal circuit 968 for 3 seconds with the ignition 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 only set as current with the ignition in the OFF position. It will become history when the ignition is turned ON. |
| • | When testing circuits to the SDGM access can be accomplished by removing the instrument panel center trim panel. Note that this procedure does not allow removal of the SDGM, only access to the connector. Refer to Instrument Panel Center Trim Panel Replacement . |
| • | Different DTCs may set in different modules along with this DTC depending on where the fault occurs and the vehicle operating conditions when the fault occurs. |
Reference Information
Schematic Reference
Connector End View Reference
Description and Operation
Data Link Communications Description and Operation
Electrical Information Reference
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. |
- Perform the High Voltage Disabling procedure.
- Ignition OFF, disconnect harness connector X1 of the BECM and the PIM.
- Reconnect the 12-volt battery.
- Ignition OFF and scan tool disconnected, test for less than 1 volt between the PIM wake up signal terminal 19 and ground.
| ⇒ | If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the SDGM. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
Control Module References for module replacement, setup, and programming
