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P0603 Nissan Code - Engine Control Module Power Supply Circuit

Quick Answer

The P0603 diagnostic trouble code for Nissan vehicles indicates a malfunction in the Engine Control Module (ECM) power supply circuit. Common causes include Faulty power supply relay or fuse, Damaged wiring harness, ECM malfunction. Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

What it means
P0603 Nissan indicates Engine Control Module Power Supply Circuit.
Common causes
Common causes include Faulty power supply relay or fuse, Damaged wiring harness, ECM malfunction.
Severity
High - diagnose this code as soon as possible.
Can I drive?
Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.
What is this?
Table of contents Created and updated by William Orellana on Aug 30, 2024
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Code P0603 Nissan Description

The P0603 diagnostic trouble code for Nissan vehicles indicates a malfunction in the Engine Control Module (ECM) power supply circuit. The ECM, also known as the engine control unit, plays a crucial role in regulating various engine functions, such as fuel injection, ignition timing, and emissions control. The power supply circuit provides the necessary voltage and current to ensure the ECM operates correctly. When this circuit malfunctions, it can lead to serious issues with the vehicle's performance and efficiency.

OBDII Code P0603 Nissan - Engine Control Module Power Supply Circuit
P0603 Nissan Code - Engine Control Module Power Supply Circuit

Common Causes of P0603 Nissan

  1. Faulty power supply relay or fuse
  2. Damaged wiring harness
  3. ECM malfunction
  4. Corrosion or poor connections in the power supply circuit
  5. Electrical issues such as short circuits or voltage spikes

Symptoms of P0603 Nissan

  1. Check engine light illuminated on the dashboard
  2. Poor fuel economy
  3. Rough idling or engine misfires
  4. Stalling or hesitation during acceleration
  5. Increased emissions

How to Fix P0603 Nissan

  1. Begin by performing a thorough inspection of the power supply circuit, checking for any visible damage or corrosion.
  2. Test the power supply relay and fuse to ensure they are functioning correctly. Replace any faulty components.
  3. Inspect the wiring harness for any signs of damage or wear. Repair or replace as needed.
  4. If the ECM is suspected to be the source of the issue, it may need to be reprogrammed or replaced.
  5. Clear the diagnostic trouble codes from the vehicle's computer and test drive to verify that the issue has been resolved.

Cost to Fix P0603 Nissan

The typical repair costs for addressing a P0603 code in a Nissan vehicle can range from $200 to $600, including parts and labor. However, it is essential to note that actual costs may vary based on factors such as the specific diagnosis time, labor rates at the auto repair shop, and the extent of the repairs needed. It is advisable to consult with a qualified mechanic or service center to obtain a more accurate estimate based on your vehicle's make and model.

What does this mean?

Tech Notes for P0603 Nissan

Start by charging the vehicles battery and clean terminal, once the battery is charged and the terminals are clean and secure, erase code. If the code comes back ON you may have to reprogram or replaced ECM

When is the Code Detected?

Indicates the ECM has experienced an internal memory fault.

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Information for Specific Nissan Models

About the author: William Orellana is a Master Mechanic and Mechanical Engineer with over 30 years of experience diagnosing and repairing vehicles. Learn more about his background.

Frequently Asked Questions about P0603 Nissan Code

1. What does the OBDII code P0603 Nissan indicate?

The P0603 code on a Nissan indicates an issue with the Engine Control Module (ECM) power supply circuit, suggesting there might be a problem with the internal memory (KAM) which can affect the settings stored in the ECM.

2. What are common symptoms of the P0603 code in a Nissan?

Symptoms can include the Check Engine Light coming on, erratic engine behavior, poor fuel economy, and potentially the engine failing to start or stalling unexpectedly.

3. What can cause the P0603 code to appear in my Nissan?

Causes of the P0603 code include a faulty ECM, poor electrical connections to the ECM, low battery voltage, or issues with the power supply circuit such as corroded or loose wires.

4. How do I fix the P0603 code on my Nissan?

Repairing the P0603 code involves checking and correcting the battery voltage if it's low, ensuring that all ECM connections are secure and free from corrosion, or replacing the ECM if it is found to be defective.

5. Is it safe to drive my Nissan with the P0603 code?

While you may be able to drive with this code active, it is not recommended as it can lead to more serious issues like engine stalling, which can compromise vehicle safety.

6. How urgent is it to address the P0603 code in a Nissan?

It is fairly urgent to address the P0603 code because prolonged issues with the ECM power supply can lead to decreased performance and potential engine damage.

7. What tools are needed to diagnose the P0603 code on a Nissan?

Diagnosing the P0603 code typically requires an OBD-II scanner, a digital multimeter, and sometimes a scope, to check the integrity and voltage of wiring and connections in the ECM power supply circuit.

8. Can a weak car battery cause the P0603 code to appear?

Yes, a weak or failing battery can cause insufficient power supply to the ECM, which might trigger the P0603 code.

9. What is the cost implication of fixing the P0603 code in a Nissan?

The cost can vary widely depending on the underlying issue. Battery replacement, if needed, can be relatively inexpensive, whereas ECM replacement can be costly, potentially running into several hundred dollars.

10. How can I prevent the P0603 code from recurring in my Nissan?

Regular maintenance of the vehicle’s electrical system, including checking the battery and ensuring all ECM connections are clean and secure, can help prevent recurrence of the P0603 code.

Discuss the causes and fixes for P0603 Nissan OBDII Code

Submit a New Comment

  • Hi this code came about since I have been having problems with my battery.I bought a new battery 4 days ago. The manager put the new battery in however I was still having to go under the hood and tap positive post to crank my vehicle. Today the check engine light came on and when I had it checked this is the code it gave, so my question is should I replace the post now?

    Reply to Comment

  • You mean replace the battery terminal? it depends how bad it is. You could just try to tighten the terminal.

    Reply to Comment

  • I check my frontier Nissan 2008 my scanner l have the light common service engine soon
    The scanner give me code p 0603 l don’t know what to do

    Reply to Comment

  • Start by charging the vehicles battery and clean terminal, once the battery is charged and the terminals are clean and secure, erase code. If the code comes back ON you may have to reprogram or replaced Engine Control Module (ECM) at the dealer.

    Reply to Comment

  • this code came up on our 2006 nissan titan. when i went to get in my truck all the dash lights were on but no key was in the ignition and it would not start. I switched a few relays and it started but It will not turn off until i take out the relays and unhook the battery cable.

    Reply to Comment

  • Do you know what relays did you swap? swapping relay is not a good idea, not all the relays are the same.
    There is a factory service bulletin that recommends checking the battery charge first and clearing the codes.
    I recommend swapping back the relays to the original place and then check the battery charge. Make sure the battery terminals are clean and tight.

    Reply to Comment

  • I have a battery disconnect to shut my battery off because It will set for a week before I run it again, would this cause this code PO603 to come on?

    Reply to Comment

    • Yes, a battery disconnect can cause P0603 on a Nissan. That code means the ECM lost its keep-alive memory power, and disconnecting the battery cuts that memory feed completely.

      If the code only appears after you use the battery disconnect and the vehicle otherwise runs normally, that may be the reason. I would still make sure the battery terminals and ECM power supply connections are clean and tight. If P0603 starts returning even when the battery has not been disconnected, then check for low battery voltage, a poor power/ground connection, or an ECM power supply circuit problem.

      Reply to Comment