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DTC U0400-U05FF

DTC U0400-U05FF

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

Refer to Control Module U Code List .

Circuit/System Description

Some control modules are constantly receiving information from other control modules through serial data communication network. The invalid data code will be set when a receiving control module detects a discrepancy in information it receives from another control module causing its integrity to be questioned. 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 V 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

Connector End View Reference

Component Connector End Views

Description and Operation

Data Link Communications Description and Operation

Electrical Information Reference


• Circuit Testing

• Connector Repairs

• Testing for Intermittent Conditions and Poor Connections

• Wiring Repairs


Scan Tool References

Control Module References 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.

3. 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 .

4. 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 after completing the diagnostic procedure.

Control Module References for control module replacement, setup, and programming