P0603 Error Code: An In-depth Analysis

The car computer, also known as the PCM or ECM, oversees all car sensors and system components in a car. In addition, it learns how you drive so it can fine-tune the system components and offer you an optimum driving experience. It assembles and stores these data in memory.

The storage memory is the Keep Alive Memory (KAM) system. The car computer continuously works with this stored information. Anytime the ECM stores P0603, it means it is not using the data on the ‘Keep Alive Memory.’ Instead, it is running on default.

Most times, the logged Error code P0603 is not common, especially on diesel vehicles. This error mainly occurs after installing aftermarket parts. This article will outline the symptoms and causes of P0603. You’ll also learn how to diagnose and fix the problem. But first, let’s look at the meaning of P0603 on Nissan Maxima and other car models. 

p0603 6.0 powerstroke

What does engine code P0603 mean?

The P0603 diagnostic trouble code is a generic code that shows the engine control module (ECM) failed to use the store information on the ‘Keep-Alive Memory’ system. As reiterated above, the KAM system should keep all your driving habits. These include data collected from the car engine timing, ignition, transmission, and ABS.

A P0603 fault code means the car computer failed to use its stored information. If you do not track and fix the root cause, the vehicle will not provide an optimal experience. In some cases, you may continually experience engine stalling and rough idling.

What is the symptom of error code P0603?

You’ll experience a few symptoms when the car computer throws a P0603 error code. At first, the check engine light will illuminate on the dashboard, followed by rough idling and engine stalling.

Here are the most common symptoms of P0603 trouble codes.

Check engine light

The car computer projects the engine warning light on the dashboard whenever it detects a problem in various system units. And the P0603 error code is no exception. So whenever you see the illumination of the check engine light on the instrument cluster, diagnose the vehicle with a scan tool. It could mean the powertrain control module (PCM) has failed to use the store data in the Keep Alive Memory (KAM) system.

Rough Idling

Another common sign of a registered P0603 error code is rough idling. Normally, default settings should not cause rough idling because new cars with no data on the KAM run perfectly fine. But, it could mean you have a lousy KAM module or a malfunctioning PCM.

Engine Stalling

Since the car computer oversees the engine timing, transmission, ignition, ABS, etcetera, and can also cause P0603 on Infiniti G35 and other car models when it fails to use the KAM data, it may cause the engine to stall. Let’s get this straight, several factors can cause engine stalling. Therefore, when your engine stalls, run a proper diagnosis to track the root cause and proffer solutions.

Increased fuel consumption

If the P0603 error code is caused by a malfunctioning engine control unit (ECU), you’ll experience bad gas mileage. This is because a malfunctioning ECU will cause several problems, including high fuel consumption.

You may notice other symptoms like

What Causes error code P0603?

Several reasons can cause the car computer to trigger error code P0603 on Ford 7.3 and other car models. Here are the common probable causes.

  • Powertrain control module wiring problems
  • Defective or malfunctioning powertrain control module
  • Ignition system wiring issues
  • Corrosion on battery terminals
  • Loose battery connections
  • Damaged KAM module.
  • Aftermarket tuning products

The repair procedures depend on the cause of the problem. For example, suppose the car computer throws a P0603 on Infiniti or any car model because you installed an aftermarket tuning product. In that case, the only solution is to replace the aftermarket product with an OEM product. Let’s see how serious the code is before discussing the P0603 fix and diagnostics.

How serious error code P0603 is?

In most cases, the P0603 on Nissan Altima and other car models is a severe issue. Because your driving habits are stored in the Keep Alive Memory system, if the car computer fails to retrieve this data, you may experience poor acceleration and rough idling. In some situations, the vehicle will take multiple kicks before starting.

Even if the vehicle runs smoothly when it starts, it may keep you stranded in the middle of nowhere. Therefore, it’s crucial to proffer solutions to the problem once you track the culprit.

How to diagnose

Learning P0603 code; how to fix and diagnose is an essential skill every DIYer should know. While some root causes of the P0603 fault code may be easy to track, others are not. In any case, this simplified guide will make diagnostics easier. Before you delve into the diagnostic procedure, you’ll need some tools and items.

Tools and Items Needed

  • Electrical contact cleaner
  • Multimeter
  • Scan tool
  • Basic hand tools
  • Car battery charger

Your car-specific repair manual

  • Start the vehicle with a recharged battery
  • Examine the battery connections. Make sure it’s well-tightened, and there is no corrosion on the terminals.
  • Inspect the wires that connect to the fuse box. If you see frayed, burnt, or damaged wires, replace them.
  • Examine the wires connecting to the engine control unit
  • Grab your multimeter and examine the voltages that are reaching the ECU. If you don’t know how to do this, check the instructions on your service manual.
  • Inspect the ECU if there’s water on it. If water enters inside this component, it will damage it.
  • Reset the ECU and test drive the car for 30 to 45 minutes. Drive as if the vehicle is working fine
  • Swap or replace the ECU if the code returns

Common P0603 diagnosis mistakes

The most common P0603 diagnostic mistake among mechanics and DIYers is replacing the powertrain control module without checking minor issues that can cause the problem.

It will save you time and money to start the diagnostics by checking battery connections and inspecting the wiring harness. You won’t want to replace the engine control unit where a loose connection or frayed wire is the root cause.

How do you fix P0603?

Always diagnose the vehicle before proffering solutions if you have a P0603 on a Peugeot boxer or any car model. Here are a few fixes that’ll rectify a P0603 fault code.

Approx. Repair Cost

If you want a service technician to track and fix the P0603, the auto mechanic will start with an hour of diagnostics. Most technicians charge $75 to $150 per hour. They’ll add the diagnostic charge to the service fee. In any case, the cost of repairing a P0603 is between $50 to $1,500. Here are estimated repair costs for individual products.

  • Tightening loose battery connection $50 to $100
  • Cleaning corrosion on battery terminals $50 to $100
  • Replace burnt, frayed, or damaged wiring harness $50 to $1000
  • Replace engine control module $600 to $1,500.

p0603 code how to fix


Q: What is a Kam error?

Auto manufacturers design cars to collect data from various system components as you drive around and store them. This is a collection of your driving habits. As the car computer monitors your driving style, it stores this information in Keep Alive Memory system.

Whenever you see a KAM error or the powertrain control module throws error code P0603, the engine control unit has failed to work with the stored information. Instead, it is working with default settings.

Q: What is Kam module?

The KAM module, also known as the Keep Alive Memory system, is where the car computer stores your driving habits. The car computer also collects this information from the KAM module whenever you start the vehicle again. By doing so, it’ll help offer the best driving experience.

Q: How do I clear keep alive memory?

A few reasons will prompt you to clear the data on the Keep Alive Memory System. For instance, if a technician replaces the electronic engine controls (EEC), he’ll need to clear the stored information from the previous vehicle. This will prevent the car computer from working with false information.

To erase the Keep Alive Memory, disconnect the negative battery terminal for around 15 to 20 minutes. After that, start the vehicle and test run it for 20 to 30 minutes. The KAM module will collect your driving style during the test run. Therefore, drive as if you’re not working on the vehicle.

Q: Where is the PCM on a 7.3 Powerstroke?

Malfunctioning PCMs are commonly the cause of P0603 code on 7.3 Powerstroke. If proper diagnostics prove that you have a malfunctioning PCM, your technician will have to find and replace it. The PCM on a 7.3 Powerstroke is located below the brake master cylinder at the driver-side firewall.

Q: What is the difference between ECU and ECM?

The ECU means engine control unit, and the ECM stands for the engine control module. These two components have different names, but technically, they mean the same thing. These modules are known as the car computer or brain of the car. They control multiple systems in a car, including the engine timing, ABS, cruise control, air conditioning systems, airbags, etcetera.

Q: What happens when you reset Kam?

A Keep Alive Memory (KAM) system reset will clear the collected data about your driving habits. In other words, it’ll unlearn your driving habits by rebooting each module on the vehicle. This will not render the vehicle inoperable. Instead, it’ll return the KAM system to default settings.

Final words

In summary, the Keep Alive Memory (KAM) system is an essential component that learns how you drive your vehicle and stores the information for an optimal driving experience. If the car computer fails to retrieve and work with this information, it’ll project the check engine light on the dashboard and throw a P0603 error code.

The P0603 is a severe case because it can keep you stranded in the middle of nowhere. We don’t want the P0603 fault code to frustrate you. That’s why we explained the meaning, causes, and the most common symptoms associated with KAM issues.

You can also diagnose and fix the root cause using the above guides. However, contact a professional mechanic if you can’t relate to the diagnosing and repair procedures or you’re not a DIYer. They will track the root cause and proffer solutions.

Osuagwu Solomon

Osuagwu Solomon is a certified mechanic with over a decade of experience in the mechanic garage, and he has over five years of experience in the writing industry. He started writing automotive articles to share his garage experience with car enthusiasts and armature mechanics. If he is not in the garage fixing challenging mechanical problems, he is writing automotive repair guides, buyer’s guides, and car and tools comparisons.

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