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MIL On With Code P0603 Stored For ECM Back Up Circuit

Models: 2015 and later Nissan vehicles. Does not apply to Titan equipped with Cummins V8 Diesel engine.

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Condition: The MIL is on with code DTC P0603 ECM BACK UP/CIRCUIT.


  1. Confirm that the battery voltage is 11 volts or more, with the ignition on and engine off.
  2. Erase DTC.
  3. Perform DTC confirmation steps in the service information.
  4. Confirm 1st trip DTC P0603 is not stored. P0603 is often the result of low battery voltage, discharged battery or battery terminal disconnections.

Service Procedure:

  1. The P0603 DTC may have been stored due to low battery voltage, discharged battery or battery terminal disconnections.
    >Confirm the battery voltage is at least 11 volts, or more, with the ignition ON.
    >While checking the battery voltage, make sure the battery cables are clean and tight.
  2. Resolve any low battery condition before proceeding. Repairs for a low battery condition are not covered by this bulletin.
  3. Connect a scan tool to the vehicle.
  4. Open C-III plus on the CONSULT PC.
  5. Turn the ignition “ON”, but Do Not Start the engine.
  6. Erase DTCs.
  7. Turn the ignition OFF.
  8. Turn the Ignition ON and wait for at least one second.
  9. Turn the ignition OFF and wait for at least 10 seconds.
  10. Repeat step 7 and step 8 ten times and then proceed to step 10.
  11. Turn ignition ON.
  12. Is P0603 currently stored as a 1st trip DTC?
    >NO: Service Procedure is complete.
    >YES: Refer to the service information section “Engine Control System” for further diagnostic information.

Courtesy of Mitchell1

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