Code P0603: All That You Need To Know

There are a lot of codes and keeping them all straight isn’t easy, which is why we created this site. So you have a place to bookmark when unfamiliar codes pop up in your diagnostics tool. This code has a specific meaning, diagnosis, and remedy, which we explain below. So why waste any more time. 

Code P0603

A P0603 comes up when the Powertrain Control Module (PCM) and it’s failure to retrieve settings from the Keep Alive Memory (KAM). It’s a low voltage issue. This code is rather universal to all cars with the OBD-II system, particularly created since 1996. Repairs, including parts and costs, are not the same no matter how generic the code is.


Powertrain control module
Image Source :

The PCM handles a myriad of responsibilities for the engine including keeping an eye on the ignition system, the fuel injection, emission systems, the position of the rotating assembly, transmission, and the exhaust.

This is basically the brain of your car. It’s the computer that controls a ton of areas in your engine that we listed above and are essential. 


The KAM adjusts the factory default settings for your vehicle regarding things like road and weather conditions and other preferences to your area. This allows you to get the best performance out of your engine. When the PCM is unable to retrieve those area-specific settings a code P0603 appears. 

When the PCM does not connect with the KAM, which is keeping track of the ever-changing needs of your specific engine and vehicle. 

Novosibirsk/ Russia – March 22, 2020: Kia Sportage, Close up detail of car engine, front view. Internal combustion engine, car parts, deteyling

Other indicators that your PCM is having a difficult time connecting with the KAM

  • Check engine light is on
  • Engine misfires
  • Difficulty starting engine
  • Shifting is badly timed
  • Acceleration and idling are rough
  • Stalling engine
  • Lowered fuel economy
  • Car dies when stopping

Note: These are also symptoms of a failed Transmission Control Module (TCM) so you never want to diagnose on symptoms alone. The diagnostic tools are essential. 

Is It Important?

This code could be a minor issue to a major problem. It all depends on what is causing this to happen and what it’s going to take to repair it. Don’t forget all the time it takes to pinpoint the issues.

Getting To the Root Of It

Cropped view auto mechanic with mud on hands fixing automobile in car repair station

Now that we know where the problem might lie, let’s take a look at some of the usual suspects for a code P0603.

  • The KAM module isn’t working correctly or is broken
  • The KAM has shorted out
  • The battery ground has shorted out
  • The KAM isn’t getting the power it needs
  • A program fault in the internal PCM
  • Damaged PCM
  • Water in the PCM or fault internally
  • KAPWR circuit has an open wire
  • Faults in the charging system or ignition system
  • Interference with the secondary ignition voltage
  • The routing of the KAPWR circuit wiring
  • Loose battery wiring
  • Battery terminal corrosion

How To Find The Problem

Step One

Mechanic troubleshooting a car engine

First, we’ll check the battery. Get the multimeter and check the voltage. If it’s below 14 volts when the car is idle or below 12 volts when the engine is turned off charge the battery. If the battery is normal then charge it anyway. It can’t hurt.

Step Two

Reset the codes and drive the car for a couple of days and then check the code again. If it shows up then you may need a new alternator or battery.

Step Three

Now you want to investigate the contacts on your battery. Keep an eye out for corrosion, excess moisture, dirt, or anything that looks like it might be getting in the way of the low voltage reading. If you find anything then make sure it is cleaned up or repaired. 

Step Four

If you’ve reached this step and the P0603 code has not been remedied then you may need to replace the entire PCM, which may require the help of a professional. 

Things To Look Out For

Man inspection holding Battery Capacity Tester Voltmeter.for service maintenance of industrial to engine repair.In Factory transport automobile automotive image

One of the most common errors people make with the P0603 is to forget to check the voltage when the car is in idle and inspecting the ground connections. But remembering to do these two things you may save yourself a good deal of money by uncovering a repair opposed to a replacement.

Another common mistake is that people replace their entire PCM without finding out whether or not there is enough voltage going to the PCM KAM circuit. If that is the issue the repair is much simpler than replacing the entire PCM. 

Some related codes include P0601 (Internal Control Module Memory Check Sum Error), P0602 (Control Module Programming), P0604 (Internal Control Module Random Access Memory (RAM), and P0605 (Internal Control Module Read Only Memory (ROM) Error. 

How To Fix It

Most P0603 codes are cleared up by the following actions. 

car mechanic at repair work with thermostat
  • Restoring faulty or damaged connectors
  • Securing all connectors
  • Using individual control modules
  • Replacing the damaged PCM

The Cost Of Repair

Depending on what caused the P0603 to appear and what you found when you did your inspection this can cost you very little or more than you are wilting to spend on a repair. Of course, the factors that play in include parts and labor, which is why DIY projects are so attractive. 


Generic codes are a bit more difficult to deal with because there are so many possible causes and solutions you start to feel like a detective more than a hobby mechanic. Now that you are familiar with the P0603 you can take your engine intrigue to the next level by checking out some of our other pieces explaining codes. 

If you enjoyed this post let us know in the comments section below. Feel free to pass this or any of our posts to your social media newsfeed or friends who are interested in fixing cars.

More Diagnostic Codes: