P0603 Code 7.3 Powerstroke – What Does it Mean? Reasons, Signs & Fixing Guide

The P0603 diagnostic trouble code that you found from your 7.3 Powerstroke engine is actually a generic or universal code that concerns the powertrain control module of the engine.

In 7.3 Powerstroke, the P0603 code refers to a malfunction in the engine control module’s Keep Alive Memory (KAM). The issues behind this code can vary from a simple dead battery to something extremely serious.

A generic code is universal for vehicles of all models and brands released from 1996 to date, but the repair process may vary a bit for different models.

In this article, we’ll take a look at the causes, signs, and fixes related to this code.

What Does P0603 Code Mean on 7.3 Powerstroke?

As I stated earlier, the P0603 DTC means that your engine’s PCM was unable to pass its Keep Alive Memory self-test. In other words, the PCM couldn’t access the data and values it stored in that memory, thus, printing this code.

This code is often found in vehicles with onboard diagnostic systems that use the KAM to store various settings and control data regarding key processes, like the transmission, ignition, engine timing, fuel-air mixture ratio, etc. 

The purpose of the KAM is to preserve important data and settings to avoid the need for reprogramming or relearning every time the vehicle is restarted.

This becomes more crucial because as the vehicle gets older, it goes through constant changes and needs further adjustment in the settings to provide optimal performance.

It also includes crucial information such as fuel trim values, idle speed settings, sensor calibration data, and other performance-related parameters.

When the KAM experiences a fault or error, it can result in the loss or corruption of data stored in the memory. This can lead to issues with engine performance, emissions, and the triggering of diagnostic trouble codes (DTCs) such as the P0603 code.

Is the P0603 Code Serious for 7.3 Powerstroke Engines?

The seriousness of the P0603 code can vary depending on specific circumstances and the extent of the issue. This code can be triggered by a petty issue like a dead battery to something way more severe and dangerous.

Access to the KAM is crucial for ensuring smoother and more efficient operation of the vehicle. As I said earlier, the more a vehicle ages, the more changes its key components go through.

That’s why older vehicles are more relied on these stored settings and adjustments and can suffer from serious performance, efficiency, and emission-related issues when the KAM malfunctions. So, the older the vehicle, the worse its P0603-related problems are likely to be. 

P0603-related issues mostly cause several engine problems like transmission operation, fuel-air mixing, engine timing, combustion, etc. Poor engine performance, such as rough idling, hesitation, misfires, or decreased power and acceleration, is often seen.

In the case of the transmission process, causing erratic or harsh shifting, difficulty in shifting gears, or transmission slipping is pretty common.

A malfunctioning KAM can also lead to increased emissions and failed emissions tests, which may trigger other emissions-related DTCs.

All these issues occur because the engine delves into a temporary dumb mode. It means the engine has no prior settings and is learning to adapt from the start.

Moreover, the PCM is one of the most crucial components of any engine. So, any DTCs that relate to it should be checked out and repaired without any delay. 

Common Signs to Detect the P0603 Code on 7.3 Powerstroke

The P0603 code will mostly be accompanied by the following signs –

  1. Illuminated check engine light (CEL) or malfunction indicator lamp (MIL)
  2. Difficult startup and engine hesitation
  3. Facing difficulty while shifting gears and badly timed shifting.
  4. Engine stalling
  5. Rough acceleration and idling
  6. Engine misfiring and transmission slipping
  7. Increased emissions and degraded emission quality

You May Like to Know: Ford 7.3 Powerstroke Engine Weight.

Common Reasons that Trigger the P0603 Code in the 7.3 Powerstroke Engines

The P0603 code can be triggered by various factors that ultimately result in a malfunction or loss of data in the control module KAM. Let’s take a look at some of the common ones below –

1. Battery Issues

Insufficient battery voltage, disconnected battery, or anything that causes disruptions in the power supply to the ECM/PCM, intentionally or unintentionally, leads to the loss of KAM data and triggers the code.

The battery voltage may be insufficient due to the battery being weak, damaged, or experiencing charging system issues. Other ways to trigger the code are when the battery is taken out for replacement, maintenance, or jump-starting.

2. Keep Alive Power (KAPWR) Circuit Malfunction

The KAPWR circuit is responsible for supplying continuous power to the engine PCM to maintain the KAM when the vehicle’s ignition is turned off. Any possible damage or fault in the KAPWR circuit may lead to the loss of KAM data.

KAPWR circuit malfunctions include damaged or loose wire, fuse or relay-related fault, or mismatched wire routing.

3. Faulty or Damaged PCM

A malfunctioning or defective PCM can lead to errors in the KAM. This can occur due to internal hardware or software issues within the module or any external damage like water intrusion.

4. Ignition System Fault

Certain issues within the vehicle’s ignition system can cause secondary ignition voltage interference, which may lead to the triggering of the P0603 code.

Various ignition faults, like a malfunctioning ignition coil, spark plug wires, or spark plugs, can generate erratic secondary ignition voltage.

Your engine’s PCM is sensitive to electrical disturbances or noise, as it relies on responding to signals for proper operation. So, if the secondary ignition voltage value is high enough, it can affect the PCM’s functionality and potentially disrupt the KAM.

Read More: Do Diesel Engines Have Spark Plugs?

Fixing the P0603 Code on 7.3 Powerstroke Engines

Pinpointing a P0603-related issue can be a bit challenging. These fixes below should help you in the process. Let’s take a look.

#1 – Inspect the Battery

Since an interrupted power supply can cause the KAM to malfunction, your first instinct with the P0603 should be to check the battery condition. Besides the battery voltage, check if there are any corroded terminals and contacts.

If the battery voltage is below 14V (idle) or 12V (engine-off), it needs a recharge. Charge the battery fully and drive the vehicle. If the code doesn’t resolve after a day or two, the issue may be somewhere else, or you may need to replace the battery or the alternator.  

#2 – Check the KAPWR Wires and Connectors

Properly inspect the wires and lines related to the KAPWR supply for loose or damaged connections. Also, check the fuses and relays related to the system for any potential faulty components.

If there is any faulty component or damaged line, fixing them should resolve the issue regarding the code.

#3 – Perform Software Update

In some cases, a software update or reprogramming of the ECM/PCM may be required. This typically needs to be done by a dealership or a qualified technician with the appropriate equipment.

#4 – Address External Interference

If your vehicle has aftermarket accessories or modifications, ensure they are not interfering with the PCM operation. Also, beware of the secondary ignition voltage interference, as they can often affect the PCM operation.

Also Check: Symptoms of a Bad IPR on 7.3 Powerstroke.


Can the P0603 code be cleared without fixing the underlying issue?

Resetting and clearing the P0603 code will temporarily remove the check engine light, but it will not fix the underlying problem causing the code. The issue should be diagnosed and resolved to prevent further complications.

Video: How To Clear Ford Keep Alive Memory (KAM) Reset Procedure

Can aftermarket modifications trigger the P0603 code?

Certain aftermarket modifications, such as incompatible performance chips or tuners, can interfere with the PCM operation and potentially trigger the P0603 code.

Will a P0603 code cause a vehicle to fail an emissions test?

It is possible for a P0603 code to cause a vehicle to fail an emissions test. Losing valuable emission system-related settings can affect engine performance and emissions quality severely.

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