What Is P0603 Code on 7.3 Powerstroke: How to Fix?

A P0603 code is one of the most common DTC (Diagnostic Trouble Codes) errors that your 7.3L engine can generate. If your code scanner shows this code, it could carry any meaning, like the small inconvenience of changing the battery. And sometimes it could mean major powertrain issues such as mistimed shifting.

If your engine gives this type of error code & you don’t know what is P0603 code on 7.3 Powerstroke, then this article may help. Check out the details on the P0603 code.  

What Is P0603 Code on 7.3 Powerstroke: How to Fix?

The P0603 code error on 7.3L Powerstroke means that the (PCM) of your car’s engine is damaged. It fails to run its own Keep Alive Memory (KAM) test.  There is a digital device in your car called PCM. It controls the necessary functions of your car, like engine timing, ignition, anti-lock brakes, etc.  

While manufacturing a car engine, PCM is programmed to run default settings. But this default is not optimal every time. 

PCM requires the adjustment data so that you can perform optimally. It computes the driving habits, weather conditions, and area of driving.  

You may make thousands of tweaks in every drive, but your PCM saves it in its Keep alive memory. But what if PCM fails? When it is unable to run this default setting after a few attempts it shows the P0603 code error. 

Related:   What is Code P1211 on 7.3 Powerstroke & How to FIx It?

Causes of P0603 Code for Your Car

Well, the P0603 code is shown because of the failure of the PCM. But there are severe causes that can damage your car’s PCM. Sometimes it depends on the difference between the default settings of your car and the new defaults manufactured.  

As your car changes after a long period of using the old default settings need adjustments.  So it is quite simple that the older the car is, the more problems you’ll face with PCM. 

Among all the problems, the most important one is the air and mixture problem and transmission issues. It also reduces the fuel efficiency of your car and causes severe damage to the engine.  

Sometimes when the engine timing problem arises, it can create unwanted tears on your engine, and faulty transmission settings can make rough shifting. 

And many users complained that their KAM module was damaged from the beginning.  So maybe it’s not always your car’s fault. It could be the default settings problem while manufacturing the car. 

Primary Symptoms Related to the P0603 Code Error

When the code scanner shows P0603 code error, you can experience any of these symptoms. Such as – 

  • Check the light of your car’s engine. Is it always on?
  • The engine creates difficulties at every starting 
  • A very rough noise and speeding up
  • Bad timing shifting
  • misfires of your engine 

TCM failure may show some of the same symptoms as this. So it is difficult to diagnose the PCM failure only with the symptoms.  So you just need one code scanner to confirm the P0603 code error.

How to Fix the P0603 Code Error on 7.3 Powerstroke?

There are so many DTC that you can diagnose and repair on your own.  P0603 code is one of the most common errors you can fix with a few DIY steps. 

But make sure you have the tools I’ve mentioned below before you go for troubleshooting the P0603 code. 

Equipment You’ll Need for Repairing P0603 Code  

  • A flashlight: To check the difficult parts of the engine 
    • A car battery charger: To charge the car battery in case it fails during the fixing 
    • A multi meter: To calculate some electrical values like the voltage, current, and resistance 
    • An OBD2 code scanner: To check the P0603 code error and confirm PCM failure. 
Related:   How to Make a 6.4 Powerstroke Bulletproof? Explained

# Diagnosing and Repairing P0603 Code Issues

If you want to fix the code permanently, you need to follow a few steps. If you are fortunate, the code can be removed by itself after a few days of uninstalling these tools. Let’s see how can you diagnose and repair P0603 code.

1. Eradicate All the Aftermarket Engine Management Products 

Manufacturing the car with aftermarket engine management goods is mostly used by the consumers. When you install any chip on your own to speed up the engine performance, it is confirmed to have a DTC error. Some users may face it earlier, some may face it after a few use. 

2. Check the Condition of Your Car’s Battery 

Here you’ll need a multi meter that is going to help you to measure the voltage of your car’s battery. If you see low voltage conditions, immediately connect the engine with the battery charger of your car.  Let the battery charge till it’s fully charged.  

Now it is time to reset those codes and let it be in rest for a couple of days. After that, check the scanner again. If so, then maybe you need to change the battery or the alternator. 

If the voltage of your car’s battery is normal, then no need to replace it.  Just connect it to the charger because it needs to be fully charged during the whole period of diagnosis and fixing.  

3. Scan Battery Associated Wiring

Check the battery wires carefully if there is any fracture or damage present.  Corrosion or loss of connection can also cause battery damage.  If you find these faults with the cables, fix the wiring or replace it. Maybe the battery problem can be fixed. 

Related:   Can I Use 5W30 Instead of 0W20? Explained (Not Recommended)

4. Check If There Is Any PCM Wiring Leakage

The PCM wiring can be a major issue in creating these error codes. So check the power-providing wires. Confirm that they are providing sufficient voltage (12.5V) to the engine. 

Sometimes the voltage may show 12.5V but check the wire again. If there is a change in voltage – it could mean that the wire is damaged or has a lost connection.

# Scan the Contacts and the Connections with Ground

If the code is still there, then you can be sure that the battery is not the problem. Now it is time for the visual scan of the battery contacts. Check if there’s any moisture or dirt which can cause the car to get low voltage, and clean it properly.

Now, disconnect the PCM, and check all ground connections to make sure that they have not been short or corroded. 

If your car still shows a P0603 code error, it is time to replace the PCM.

# Install the Latest PCM Software 

Sometimes the manufacturers launch new PCM software without people’s awareness at the starting. So what if you are running the outdated PCM? It must result in a P0603 error code.

So go to the nearest dealer & update your   PCM to the latest version. This time it is almost confirmed that you will not get the P0603 code again. But in the rare case, if you still see the code, just replace the PCM. 

Final Words

So, now you know what is P0603 code on 7.3 Powerstroke and how to fix it. Our guide will be pretty much enough for you. However, if you still face any complication, feel free to seek expert’s help.

Read More:
What Are the Symptoms of a Blown ECM Fuse? Explained
What Is P1316 Code on 7.3 Powerstroke and How to Fix It?
What Is P20BA Code on 6.7 Powerstroke and How to Fix It?
Signs and Symptoms of Bad MDS Solenoid (Explained)

Rate this post

Brian Polk

Brian is an automotive expert who has 12 years of experience in the industry. He has worked on a variety of cars, from high-end luxury vehicles to budget-friendly options, and has a wealth of knowledge on the subject. He is passionate about automobile and enjoys sharing his knowledge with others, whether they are looking to purchase a new motorized vehicle or simply learn more about the inner workings of these machines. In his free time, Brian enjoys working in his automobile workshop and spending time at the track.

Recent Posts