U18B9

DTC U18B9-U18BF

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 U18B9

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Primary High Speed CAN Bus Subnet Configuration List

DTC U18BF

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Secondary High Speed CAN Bus Subnet Configuration List

For symptom byte information, refer to Symptom Byte List Symptom Byte List.

Circuit/System Description

Devices on the high speed GMLAN serial data bus and the chassis high speed GMLAN serial data bus must be programmed with software that specifically identifies the correct type and quantity of devices on the bus based on RPO configuration. If a device was not properly configured after installation, the appropriate U Code may be set for that device. No external circuit diagnosis is involved.

Conditions for Running the DTC

* Voltage supplied to the device is in the normal operating voltage range.

* The vehicle power mode requires serial data communication to occur.

Conditions for Setting the DTC

* The device is not configured properly.

* Control unit recognizes a programming error.

* CAN-Bus configuration is invalid

Conditions for Clearing the DTC

* A current DTC clears when the malfunction is no longer present.

* A history DTC clears when the device ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.

Reference Information

Schematic Reference

* Data Communication Schematics [1][2]Electrical Diagrams

* Control Module References Control Module References

Connector End View Reference

Component Connector End Views Fuel Pump and Level Sensor Assembly

Description and Operation

Data Link Communications Description and Operation Description and Operation

Electrical Information Reference

* Circuit Testing Circuit Testing

* Connector Repairs Connector Repairs

* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections

* Wiring Repairs Wiring Repairs

Scan Tool Reference

Control Module References Control Module References for scan tool information

Circuit/System Verification

1. Ignition ON.

2. Verify DTC U18B9-U18BF is not set.

• If DTC U18B9-U18BF is set along with other DTCs set

Diagnose all other DTCs first. Refer to Diagnostic Trouble Code (DTC) List - Vehicle Diagnostic Trouble Code (DTC) List - Vehicle.

• If DTC U18B9-U18BF is set without other DTCs set

1. Program the device that set the DTC.

2. Ignition OFF, remove the scan tool, open and close the driver door. Wait 60 seconds.

3. Verify the DTC does not set.

• If the DTC sets, replace the appropriate device.

• If the DTC does not set

4. All OK.

• If DTC U0400-U05FF is not set

3. All OK

Repair Instructions

Perform the Diagnostic Repair Verification Verification Tests after completing the repair.

Control Module References Control Module References for device replacement, programming and setup