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 U209A 00: High Speed Communication Enable Circuit LowDiagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
Ignition Voltage (Circuit 2139) | P2534* ** | P2534** | U209A** or B1453 | -- |
Ignition Voltage (Circuit 239) | B1453* ** | B1453** | U209A** or B1453 | -- |
Communication Enable Signal (Circuit 5986) | U209A** or U2099 | U209A** | -- | -- |
Wake Up Signal (Circuit 5985) | U1814* | U1812* | U209A* | -- |
* Circuit fuse will open ** May set other module/DTCs. | ||||
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.
Wake up signal circuits are energized by the body control module (BCM) to activate the serial data gateway module (SDGM) and other modules, including the BECM, immediately when serial data is required. Additionally after receiving this signal the SDGM energizes another wake up signal to activate the drive motor generator battery control module (BECM) among others.
Conditions for Running the DTC
| • | The system voltage is between 9-16 volts. |
| • | The ignition key is OFF. |
Conditions for Setting the DTC
| • | The communication enable signal circuit is open/high resistance. |
| • | The wake up signal circuit is shorted to voltage. |
Action Taken When the DTC Sets
The MIL may illuminate and the DIC may display multiple messages.
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 .
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, ensure the following DTCs are not present in the modules as follows:
BCM
| • | U1814 |
| • | U2099 |
SDGM
| • | U1812 |
| • | B1453 |
| ⇒ | 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 the harness connector X2 at the SDGM.
- Verify less than 0.5 volts between the wake up signal circuit terminal 19 and ground.
- Ignition ON, verify B+ between the communication enable signal circuit terminal 16 and ground.
- If all circuits test normal, replace the SDGM.
| ⇒ | If greater than the specified range, test the circuit for a short to voltage. If the circuit tests normal, replace the BCM. |
| ⇒ | If less than the specified value, test the circuit for an open/high resistance. If the circuit tests normal, replace the BCM. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
