U0400
DTC U0400-U05FF
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
Control Module U Code List.
Circuit/System Description
Some control modules must be configured with specific software, serial numbers, vehicle options, or other information. If a control module was not properly configured after installation that module may set the appropriate U Code. The symptom byte listed in the DTC Descriptor is for engineering reference only. No external circuit diagnosis is involved.
Conditions for Running the DTC
Battery voltage is between 9-16 volts and data link communications operate normally.
Conditions for Setting the DTC
The control module is not configured properly.
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 (with WHB) (Data Communication Schematics (with WHB))Data Communication Schematics (without WHB) (Data Communication Schematics (without WHB))
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. Engine running for 10 seconds.
2. Ignition ON, engine OFF, verify the DTC U0400-U05FF is not set.
• If the DTC U0400-U05FF is set along with other DTCs set, diagnose all other codes first. Refer to Diagnostic Trouble Code (DTC) List - Vehicle (Diagnostic Trouble Code (DTC) List - Vehicle).
• If the DTC U0400-U05FF is set without other DTCs set, program the control module specified by the DTC descriptor. If the DTC resets, 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