Possible Battery Issue
This bulletin applies to 2015 and later Nissan Frontier vehicles equipped with a 4.0L engine. If you confirm that the MIL is on and DTC P0603 (ECM back up/circuit) is stored, confirm that the battery voltage is 11 volts or more with the ignition on and engine off.
Erase the DTC and perform DTC confirmation steps in the service procedure. Confirm 1st trip DTC P0603 is not stored. DTC P0603 is often the result of low battery voltage, a discharged battery or battery terminal disconnections.
The specific steps are as follows:
1. Confirm battery voltage with ignition on/engine off. While checking voltage, make sure that battery cables are clean and tight. Resolve any low battery issues before continuing.
2. Connect C-III plus VI to the vehicle.
3. Open C-III plus on the CONSULT PC.
4. Turn the ignition on, but do not start the engine.
5. Erase DTCs.
6. Turn the ignition off.
7. Turn the ignition on and wait for at least 1 second.
8. Turn the ignition off and wait for at least 10 seconds.
9. Repeat step 7 and 8 TEN times, then proceed to Step 10.
10. Turn the ignition on.
11. If P0603 is not stored as a 1st trip DTC, the procedure is done. If the code appears again, continue diagnostics referring to the electronic service manual section Engine Control System.