P0603 is a generic OBD2 fault code. It indicates that the maintenance memory of your Nissan Murano has had an error.
Life maintenance memory is the data that your Murano’s PCM (Powertrain Control Module) has learned about the health of your engine. All of this sensor and driving data is used to maintain efficient operation. Keep-life memory requires battery power to maintain stored data and will be erased on battery power.
When the life support memory fails (such as when you unplug the battery) your Murano reverts to the default values that were programmed into the memory at the factory. Typically, there will be no noticeable difference in engine performance when this occurs, unless the PCM is compensating for an engine problem.
P0603 Symptoms: Nissan Murano
The only symptom of P0603 may be the check engine light. This is especially true if the life-sustaining power circuit has failed. You may notice that the engine stalls or that your Murano does not start at all.
P0603 Causes and Diagnosis: Nissan Murano
These are the most common causes of P0603:
A good place to start to see what is causing P0603 on your Murano is the battery terminals. If they are loose, damaged, or corroded you can reset the life support memory. This will force the PCM to return to factory specifications and throw the code.
Check the battery cables and make sure they are not corroded and are tight. If they are, make sure the wiring from the battery terminal to the fuse box is correct. Make sure the ground wiring is not corroded.
A good trick to see if the charging system is faulty is to erase the code (you will need a good scanner) and disconnect the alternator. Now start your Murano and see if the P0603 comes back. If it does, it indicates that you probably have a bad alternator or voltage regulator.
Check the wiring harness around the coil packs. Look at the spark plug wires. Check the coil packs for cracks. You’re looking for something that may be putting strain on your Murano’s wiring harness.
A proven trick is to wait until it’s dark and start the engine. You should see the spark “bleed” from the ignition system if there is a problem with it.
A faulty PCM can, and often does, cause P0603. Water damage is an especially common culprit. Vibrations or a power surge can also damage it. Don’t start with the PCM, but if you don’t find any obvious problems, it may very well be the problem.
The keep-alive memory circuit may have an open circuit or a short circuit. In that case, life support data cannot be recorded at all. Check the tension and move the harness. Check if it remains constant.
Conclusion: P0603 Nissan Murano
P0603 can be a difficult code to locate. It could be a wiring problem or a bad PCM. If there is anything you would like to add that might help someone with their Nissan Murano, leave a comment below. Good luck!