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U0401 Network

Invalid Data Received from ECM/PCM

The ECM/PCM is present on the data bus but the values it reports are implausible — out of range, frozen, or failing the checksum or rolling-count check. The receiving modules reject the data. Implausible engine data can force limp mode or stall the engine. Causes include a faulty sensor feeding the module, internal computation errors, a software or calibration mismatch after a repair, or bus interference corrupting the frames.

Affected components

  • Ecm
  • Can bus wiring

Common causes

  • Medium likelihood: ECM software bug or outdated calibration
  • Medium likelihood: ECM internal sensor or processing fault
  • Medium likelihood: CAN corruption causing checksum errors

Possible symptoms

  • Multiple warning lights may illuminate
  • Affected modules may go into limp mode or shut down
  • Specific functions inoperative depending on module
  • Diagnostic tools may show communication faults

Diagnostic notes

  • The malfunction indicator lamp may illuminate
  • This code can affect emissions
  • Reduced-power or limp mode may occur

Sources

Diagnostic information is provided for reference only. Confirm the code with a compatible scan tool and follow the vehicle manufacturer's service procedures before replacing components.

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