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P0603 Code: How to Fix This Engine Error Code!

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The check engine light turns on while you’re driving, and there happens to be a misfiring from the engine while you’re driving. It can be quite a hassle while you’re driving to your home or workplace. Using the OBD-II scanner detects that your car activated the P0603 code. But what does that imply? 

A P0603 code indicates that your car’s powertrain control module (PCM) has detected an unexpected error in its Keep Alive Memory (KAM). It differs from the ‘limp’ mode because the PCM does not detect a fault. The PCM memory hasn’t got updated to reflect the required engine parameters. Though the code is a generic engine error code, the repair steps may vary based on the model. 

That is why it is critical to determine the P0603 code meaning and examine the causes. Our article also covers its typical symptoms and how to fix the error code! 

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What does code P0603 mean? 

The code implies that the PCM failed the Keep Alive Memory (KAM) self-test. The code gets stored when the PCM works on its default parameters. In contrast, it should be working with the information stored from drive cycles. The memory stored in the PCM is the drive cycle, also known as the Keep Alive Memory (KAM). 

This memory constantly varies in response to the two major driving and sensor inputs. However, when the battery is disconnected, this memory gets erased. The PCM enters ‘numb’ mode when and when this memory gets erased. It is because the KAM runs the engine using the built-in parameters. Though the code applies to all OBD-II-equipped cars, the definition, troubleshooting methods, and repairs vary slightly from one car model to another.  

How serious is the P0603 code? 

The seriousness of the code differs based on the car model. The issue may be minor and insignificant with a brand-new car without much of a KAM change. The problem can be very serious and have adverse consequences for an older car that stores much information in its KAM. This code could indicate a simple problem with your battery or a serious problem with your car’s PCM. If the code implies a problem with your car’s PCM, it is vital to discover the issue immediately. 

Is it safe to drive with code P0603? 

Ideally, you can drive with this code for a short distance, like to a nearby repair shop. You shouldn’t have serious enough problems that you need to consider the safety of your car, particularly if this is your only issue. However, you can note a decrease in driving quality until this error code gets resolved and you can access the KAM module again. 

What causes code P0603?  

A lot of issues can lead the code to appear. However, these faults are typically associated with the PCM, battery connection, and KAM system connection.  

  • Corrosion of battery terminals or loose connections 
  • Circuit wire routing for Keep Alive Power (KAPWR) 
  • The KAPWR circuit has an open wire 
  • Faulty PCM, water intrusion, or an internal fault 
  • Faulty charging system 
  • A fault in the ignition system fault causes secondary ignition voltage inference 
  • Fault in the internal PCM program 
  • Battery charge is low 

What are the symptoms of the P0603 code? 


Like most engine error codes, the most evident symptom of this error code will be the check engine light illuminating. The following are other symptoms you can observe. 

  • It isn’t easy to start the car’s engine 
  • Acceleration and rough idling 
  • The transmission shift gets bad 
  • Misfires in the engine 
  • Other warning lights illuminates 
  • The engine stalls 
  • Rough running/idle  
  • Emission test fails 
  • The traction control/ABS light turns on 

How do I fix code P0603? 

Solving complex issues will require the help of a mechanic. But if the car activates the code, you can easily check for some common issues with your car’s battery. 

Check the voltage of your battery 

Your battery may not always supply enough power to the PCM. Then check your battery with a multimeter. You must charge the battery if the voltage is less than 12 volts with the engine off or less than 14 volts with the engine idling. Do a replacement if the battery is over four years old. Reset the code and check if it reappears after a few days of driving. 

Inspect your battery contacts 

Examine your battery contacts as well. The car’s battery will overcharge if the contacts are corroded or dirty. 

What repairs can fix code P0603? 

After successfully diagnosing your car with this code, do the following repairs to ensure the code gets successfully cleared. 

  • Consider replacing your alternator and battery. 
  • Repair or replace faulty or damaged connectors, wirings, and components, and ensure that the components are securely connected. 
  • Replace or repair all defective components in individual control modules. 
  • Consider replacing any damaged PCM or battery grounds. 

How much does it cost to fix the P0603 code? 

It may take time to solve the issue. Suppose the issue is with your car’s battery. Then a professional will charge between $180 and 230 for replacement, depending on the make and model of your car. If the PCM becomes faulty, it will cost you $1,000. The repair shops ideally charge between $75 and $150. 

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