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
- Primary High Speed CAN Bus Subnet Configuration List

DTC U18BF
- Secondary High Speed CAN Bus Subnet Configuration List

Circuit/System Description

Control modules 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 modules on the bus based on RPO configuration. If a control module was not properly configured after installation, the appropriate U Code may be set for that module. No external circuit diagnosis is involved.

Conditions for Running the DTC

* Voltage supplied to the module is in the normal operating voltage range.
* The vehicle power mode requires serial data communication to occur.

Conditions for Setting the DTC

* The control module 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 module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.

Reference Information
Schematic Reference

Data Communication Schematics (Electrical Diagrams)
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 (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 References

Control Module References (Programming and Relearning) for scan tool information

Circuit/System Verification

1. Verify the appropriate DTC is not set.

• If the DTC is set along with other codes, diagnose all other codes first. If no other codes are set, program the control module that set the DTC.

2. With a scan tool, clear the DTCs.
3. Ignition OFF, remove the scan tool, open and close the drivers door.
4. Wait 60 seconds, then verify the DTC is not set.

• If the DTC is set, replace the appropriate control module.

Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.

Control Module References (Programming and Relearning) for control module replacement, setup, and programming