EGR Not Ready: Meaning, Causes and Fixes

Getting the Exhaust Gas Recirculation (EGR) monitor can be daunting. What’s more challenging is when your car displays the notorious ‘EGR not ready.’ Guess what? Yet, you’ve added more miles to your car and the check engine light doesn’t illuminate. 

What should do if this happens? I’ve taken out time to provide useful insights into what the EGR means.

Plus, what causes the EGR monitor to indicate ‘not ready.’. You’ll also learn what fix to apply if this code shows up during EGR scanning. Let’s take the walk together. 

What is the EGR?

To understand what the ‘EGR flow not ready’ means, let me explain how the EGR monitor itself works and what it does. Exhaust Gas Recirculation is a technique in your vehicle’s engine management system.

It’s responsible for reducing nitrogen oxide emissions. This emissions assembly subsystem helps reduce pressures and temperatures in the combustion chambers. This way, it regulates how much nitrogen oxide emits. 

The EGR components are an actuator solenoid, an EGR valve, and differential pressure sensors. The latter is called the DPFE. When these parts sync, they ensure that your car engine works with the accurate amount of gas recirculation, relative to the engine load and temperature.

The EGR monitor is designed to check the issues with your car components, especially the emissions assembly. However, an ‘EGR not ready’ outcome will mean that the system monitor isn’t able to check for these problems. 

The components of the emission controls are in sound health and working perfectly. But if the monitor cannot determine the health of this system, the OBD checks will be incomplete.

As an onboarding computer system, the EGR system monitors and reports all problems. These include high gas consumption, excessive exhaustive emissions, and poor engine performance. 

Causes of EGR not Ready

Many issues can be responsible for code P0401 to display. But, the five common causes of a malfunctioning EGR monitor or valve are:

  • Recent Battery replacement 
  • ECU Memory resetting
  • Emissions control system problem 
  • Software Updates 
  • Component Replacement or Repair

Recent Battery Replacement 

One of the common reasons the EGR monitor will display the infamous ‘not ready’ is if you recently replaced your car battery. This sign will also show if the battery is disconnected or has no charge left in it.

As a rule of thumb, you’ll need to disconnect your battery’s black terminals when you want to replace the EGR valve.

After replacement, the EGR monitor may not immediately be ready to complete a self-test.

Likewise, it won’t detect any problems with the components or emission assembly.

ECU Memory Reset

Resetting your car’s Electronic Control Unit, ECU means using scan tools to wipe off all the long-standing data on the ECU memory. This process will require you to disconnect the battery for a few minutes.

You will then reconnect it, before driving the car for about 10 miles. While this is on, the EGR valve may be affected, causing the EGR monitor to fail to detect any component problem.

In the process, the ECU will store all diagnostic trouble codes. 

Emissions Control System Problem 

Any issue with the emission assembly will prevent the EGR monitor from self-testing. Emission control problems can result from a wide range of reasons.

A faulty oxygen sensor is a major culprit as it indicates whether your car is running too lean or too rich. It also monitors the rate at which the engine burns fuel.

Yet, if it fails, the emission control system will not work as it should. The result is that the EGR monitor does not determine any problem or self-test. 

Software Updates 

Once you carry out any software update on your car, there is a chance that the EGR will temporarily falter. Until you carry out the road testing, you may not be able to enjoy the optimal function of the EGR monitor. 

Recent Component Replacement or Repair

If you recently carried out a major repair on your car, there’s a chance that the EGR monitor won’t work. Repairs usually could affect the functionality of the monitor. 

How to Fix EGR Not Ready

To fix the EGR Not Ready, you need to take the car through a readiness test, also called a road test. Here are steps to carry out the road tests to fix the EGR not ready issue. 

Step 1: Park your vehicle

Park the car and allow the engine to cool for at least 8 hours. Refill your gas tank up to three-quarters (75%), or at least a little above one-quarter (15%). Make sure the initial coolant temperature ranges from 0oF-104oF. 

Step 2: Start the engine

The next step is to start your car engine and allow it to idle for 3-5 minutes. Switch off all accessories, including the rear defroster and air conditioner.

Step 3: Turn off the AC and Defroster

While the air conditioning system and defroster are off, speed up your car up to 50 mph within 15 seconds.

Then engage the vehicle’s 4th gear and drive the car for about 10 to 15 minutes at highway speeds.

Continue with driving the car for another 20 minutes. But this time, drive in stop-and-go traffic. 

Step 4: Decelerate and brake

Make sure you maintain the steady 50mph speed in the 4th gear for up to 5 minutes or so without interruptions.

Decelerate by braking down to 45 mph with the same gear for another 3 seconds or so. 

Step 5: Increase speed to full throttle 

Increase in full throttle up to a speed of 55 mph with 4th gear for 3 seconds. Decelerate and brake speed again to 45 mph for 3 seconds.

Repeat the acceleration and deceleration procedures a few more times and finish at 55 mph.

Step 6: Finish the process

Stop the vehicle, park it, and allow it to idle for about 5 minutes. By this time, the EGR system readiness monitor should be complete and the EGR should show ready.

If the process is unsuccessful, you can repeat it until the system displays ‘EGR ready.’ 

Read more:

Can EGR Monitor be Replaced? 

Unfortunately, you cannot replace the EGR monitor. ‘Why?’ you may want to ask. The EGR system monitor performs emission controls which are essentially internal self-test.

The process of self-testing different emission controls is a Drive Cycle. The EGR monitor is not a smog component of the car. The EGR monitor, through the ECU, ensures the car is running efficiently without polluting through emissions. 

Final Thoughts

Once you notice the EGR-not-ready code, it’s time to take your car to the technician for a prompt diagnosis. I hope you found this article helpful as you drive around. Remember to make safety your watchword. Like I always say: no auto fault is too small to ignore or too big to resolve. 

  • James Smith

    I'm James Smith, a car enthusiast and a content writer for Daily Car Tips. I have a passion for all things cars, from classic muscle cars to the latest electric vehicles. When I'm not writing about cars, you can usually find me tinkering with my car or checking out the latest automotive trends.

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