P0603 Code – Meaning, Causes, Symptoms (& How To Fix)

P0603 - Internal Control Module Keep Alive Memory (KAM) Error

P0603 Trouble Code

When you get the P0603 code on your OBDII scanner, you might wonder how difficult of a fix you are facing. In some cases, it’s an easy fix, but it can also be something complicated. 

That’s why it’s important to figure out the P0603 meaning and examine the causes. We will also look at the P0603 symptoms and show you the possible solutions. 

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Code P0603 Definition

P0603 – Internal Control Module Keep Alive Memory (KAM) Error

What Does the P0603 Code Mean?

The P0603 code is a generic trouble code that shows the Powertrain Control Module (PCM) failed the Keep Alive Memory (KAM) self-test. This memory is required to keep all of the driving information for the transmission, engine timing, ignition and ABS stored. 

The PCM is the main computer that regulates numerous systems in the vehicle. It’s programmed to have factory default settings, but these aren’t always ideal for your driving style. Over time, the PCM makes adjustments to these settings so the car is better suited to your needs. 

Instead of making these changes every time you start the vehicle, the PCM stores these settings in the Keep Alive Memory. If the settings can’t be retrieved when you start the car, the P0603 alerts you to trouble. 

RELATED: 6 Symptoms of a Bad PCM (& Replacement Cost)

P0603 Trouble Code Symptoms

The most common P0603 code symptom will be that the Check Engine Light comes on. You could also notice difficulty starting the engine and performance issues.

Here are the most common symptoms:

  • Check Engine Light
  • Engine difficult to start
  • Rough acceleration/idling
  • Issues with shifting
  • Misfires
  • Stalling

Causes of the P0603 Code

Several issues can cause the P0603, from simple electrical problems to a malfunctioning sensor.

Here are the most common causes:

How Serious is the P0603 Code?

High – In some rare cases, you might notice any other symptoms with the P0603 code, but that’s not normally what happens. Because the KAM holds the performance settings, the inability to get this powered up means that acceleration, idling and starting the car can all be hindered.

Even if the car runs okay at first, it could quickly create issues while you are away from home. Resolve the problem quickly to avoid getting stranded in a remote location. 

What Repairs Can Fix the P0603 Code?

Here are a few repairs that might resolve the P0603 trouble code. You should always perform a proper diagnostic before replacing expensive car parts.

  • Clean off battery corrosion, re-establish the connection
  • Replace defective KAM wiring
  • Replace PCM

Common P0603 Diagnosis Mistakes

Many people jump right to replacing a PCM that isn’t defective. In fact, the performance issues alone might make one think that the PCM is to blame, but it can be any number of smaller issues. 

You don’t want to replace the PCM when the root problem comes down to a bad connection. Replacing a battery or checking the wiring is a much easier and less expensive fix, so that’s where you should start. 

Recommended Tools for Diagnosis

How to Diagnose the P0603 Trouble Code

It’s not always easy figuring out the P0603 code, but these steps can set you on the right path.

  1. Start with a fully charged battery.
  2. Inspect the terminals and connections for corrosion. Ensure everything is making a good connection and nothing is loose.
  3. Check the wires going into the fuse box wiring harness. If anything is damaged, replace it.
  4. Check the wiring going to the PCM. If anything is damaged, replace it.
  5. Measure voltage going to the PCM. You should be able to get more guidance on how to do this from your service manual. 
  6. Look for any signs of water near the PCM. Any intrusion can damage the module.
  7. Flash the module and set it to default settings. Try driving the car again to see if the code re-emerges. 
  8. Replace the PCM. 

Estimated Cost of Repair

The cost to repair the P0603 code can range widely from a few dollars to several hundred. 

  • Battery Corrosion Cleaning – the cost of supplies
  • Replace wiring – $50-$1,000
  • Replace PCM – $700-$1,500

Mechanics Tips about the P0603 Code

If you are using an aftermarket tuner, this could be creating issues. Take the tuner off of the car and see if it still exists.

Additionally, it’s possible to see other trouble codes with the P0603 alert. Here are a few you might see:

  • P0607 – Control Module Performance error
  • P0605 – Internal Control Module Read Memory (ROM) Failure
  • P0604 – Internal Control Module Random Access Memory (RAM) Error
  • P0601 – Internal Control Module Memory Check Sum Error
  • P0600 – Serial Communication Error

If any of these trouble codes exist with P0603, you want to troubleshoot and repair these first. Any one of them could resolve the other problem or at least help you figure it out.