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 Descriptor
DTC U182A 00: Lost Communication With Battery Energy Control Module on Bus BDiagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
B+ From 200 A Mega fuse | U182A* | U182A* | -- | |
PTLAN + 2 circuits at EBCM | U0074* | U182A* | U0074* | -- |
PTLAN - 2 circuits at EBCM | U0074* | U182A* | U0074* | -- |
Wake Up Signal circuit 932 | B137B* | U182A* | U189A* | -- |
* Other modules/DTCs will set with this fault. | ||||
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 module (SDGM) energizes the wake up signal to activate the accessory DC power control module (APM) when communication is needed. The SDGM monitors the signal circuit for faults.
Conditions for Running the DTC
| • | The system voltage is between 9-16 volts. |
| • | The ignition in RUN. |
Conditions for Setting the DTC
| • | The APM wake up signal is open. |
| • | The APM does not receive battery voltage. |
| • | The PTLAN circuits between the SDGM and the APM are open. |
Action Taken When the DTC Sets
The modules is never signaled, therefore the specific subsystems may not function. Depending on the fault, the MIL, battery indicator may illuminate and several DIC messages be present.
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
| • | 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 Verification
With a scan tool, verify that DTC B137B or U189A are not present in the SDGM.
| ⇒ | If any listed DTC is present, refer to Diagnostic Trouble Code (DTC) List - Vehicle to diagnose that DTC prior to this diagnostic. |
Circuit/System Testing
- Ignition OFF, disconnect harness connector X1 of the APM.
- Ignition ON, test for B+ between the wake up signal circuit terminal 3 and ground.
- Ignition OFF, disconnect harness connector X3 of the APM.
- Ignition ON, test for B+ between the B+ circuit terminal 1 and ground.
- Disconnect harness connector X1 of the EBCM.
- Test for less than 1.0 ohm between the APM and the EBCM on the following circuit terminals.
- Ignition OFF, disconnect harness connector X1 of the SDGM.
- Test for less than 1.0 ohm between the EBCM and the SDGM on the following circuit terminals.
| ⇒ | If less than the specified value, test the circuit for an open/high resistance. If the circuit tests normal, replace the SDGM. |
| ⇒ | If less than the specified value, test the circuit for an open/high resistance. If the circuit tests normal, replace the SDGM. |
| • | PTLAN + APM terminal 5 and EBCM terminal 33 |
| • | PTLAN - APM terminal 4 and EBCM terminal 21 |
| ⇒ | If greater than the specified range, test the circuit for an open/high resistance. |
| • | PTLAN + EBCM terminal 34 and SDGM terminal 13 |
| • | PTLAN - EBCM terminal 22 and SDGM terminal 11 |
| ⇒ | If greater than the specified range, test the circuit for an open/high resistance. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for module replacement, setup, and programming |
