P1604: Code Word Unregestered

MediumPowertrainEngine/Powertrain

What does P1604 mean?

P1604 is a diagnostic trouble code indicating "Code Word Unregestered". This code relates to your vehicle's engine/powertrain and should be diagnosed to determine the root cause. The severity level helps indicate how urgently this should be addressed.

Common causes

  • Faulty engine/powertrain component
  • Wiring or connector issue in the related circuit
  • Failed sensor providing incorrect readings
  • Software/calibration issue requiring ECU update
  • Related component causing secondary fault

What should you do?

Schedule a diagnostic appointment at your earliest convenience. The vehicle is generally safe to drive short distances, but the underlying issue should be addressed to prevent it from worsening.

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Code P1604 can mean different things depending on your vehicle. TorqueBot gives you a diagnosis specific to your make, model, and year.

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Related codes

P1603EEPROM Malfunction
P1605Keep Alive Memory Test Failure
P1602Immobilizer/ECM Communication Error
P1606ECM Control Relay O/P Circuit Malfunction