U209A
DTC U209A
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview) provides an overview of each diagnostic category.
DTC Descriptor
DTC U209A 00
- High Speed Communication Enable Circuit Low
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.
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.
Reference Information
Schematic Reference
* Data Communication Schematics (Electrical Diagrams)
* Control Module References (Programming and Relearning)
Connector End View Reference
Component Connector End Views (Connector Views)
Description and Operation
Data Link Communications Description and Operation (Description and Operation)
Electrical Information Reference
* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)
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 (Diagnostic Trouble Code Descriptions) to diagnose that DTC prior to this diagnostic.
Circuit/System Testing
1. Ignition OFF, disconnect the harness connector X2 at the SDGM.
2. Verify less than 0.5 volts between the wake up signal circuit terminal 19 and ground.
• If greater than the specified range, test the circuit for a short to voltage. If the circuit tests normal, replace the BCM.
3. Ignition ON, verify B+ between the communication enable signal circuit terminal 16 and ground.
• If less than the specified value, test the circuit for an open/high resistance. If the circuit tests normal, replace the BCM.
4. If all circuits test normal, replace the SDGM.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
GMLAN Wiring Repairs (Component Tests and General Diagnostics)