• 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.

Refer to Control Module U Code List.

Some devices are constantly receiving information from other devices through serial data communication network. The invalid data code will be set when a receiving device detects a discrepancy in information it receives from another device 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.

Battery voltage is between 9–16 V and data link communications operate normally.

The device is not configured properly.

• 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.

This diagnostic procedure can be used to diagnose these common DTCs: U0400, U0401, U0402, U0403, U0404, U0405, U0406, U0407, U0408, U0409, U040D, U040F, U0410, U0414, U0415, U0416, U0417, U0418, U041B, U041E, U0420, U0421, U0422, U0423, U0424, U0425, U0426, U0427, U0428, U0429, U042B, U042E, U0430, U0431, U0432, U0433, U0435, U0436, U0437, U0438, U0439, U043A, U043B, U043C, U0440, U0447, U0452, U0456, U0459, U045A, U0461, U0462, U0463, U0464, U0465, U0466, U0467, U0468, U0469, U046A, U046B, U046C, U046D, U0481, U0482, U0483, U0485, U0486, U0492, U0493, U0497, U0498, U0499, U04B1, U04B5, U0507, U0508, U0513, U0514, U0515, U052A, U0532, U0533, U0534, U0536, U0537, U053B, U053C, U053D, U0546, U0549, U054B, U0551, U0555, U0558, U0563, U0564, U0565, U056B, U056E, U0585, U0586, U0588, U0594, U0595, U0596, U059B, U05A1, U05A2, and other DTCs within U0400–U05FF range.

• Data Communication Schematics
• Control Module References

Master Electrical Component List

Data Link Communications Description and Operation

• Circuit Testing
• Connector Repairs
• Testing for Intermittent Conditions and Poor Connections
• Wiring Repairs

Control Module References for scan tool information

1. Engine running for 10 s.
2. Ignition ON/Vehicle In Service Mode, engine OFF, verify DTC U0400-U05FF is not set.
• If DTC U0400-U05FF is set along with other DTCs set or symptoms

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

• If DTC U0400-U05FF is set without other DTCs set or symptoms
1. Program the device specified by the DTC descriptor.
2. Verify the DTC does not set.
• If the DTC sets, replace the appropriate device.
• If the DTC does not set
3. All OK.
• If DTC U0400-U05FF is not set
3. All OK

Perform the Diagnostic Repair Verification after completing the repair.

Control Module References for device replacement, programming and setup