How to Fix a P0401 Code on Chevy (Step by Step – Solved!)

P0401 Code Chevy

Do you know how to fix a P0401 code on Chevy vehicles (models like Silverado, Impala, Malibu, Volt, Duramax, Equinox, Uplander, and Monte Carlo)? this is one of the questions our readers ask a lot. Well, we´ve got you covered.

Having to deal with the pesky P0401 code on a Chevy can be a real pain on some of their models.

Especially on smaller ones, with crowded engine bays such as Volt.

But in case that you are experiencing this code, your Chevy will very likely fail the emission testing.

Additionally, because this is a permanent code, your vehicle can fail the vehicle inspection.

So, how to fix a P0401 code on Chevrolet vehicles? To fix a P0401 code on Chevy vehicles (models like Silverado, Impala, Malibu, Volt, Duramax, Equinox, Uplander, and Monte Carlo) you need to follow the steps below:

  • Step #1 Check EGR valve
  • Step #2 Check EGR pipe
  • Step #3 Check EGR cooler
  • Step #4 Check EGR passages

Meaning: What is the P0401 Code on Chevy

The P0401 code (Exhaust Gas Recirculation Flow Malfunction) is one of many standard OBD-II diagnostic trouble codes and it stands for EGR insufficient flow detected.

Exhaust Gas Recirculation or EGR is a system for decreasing the emissions of the internal combustion engines.

Primarily it decreases the generation of NOx by decreasing the temperature in cylinders during the combustion.

This is done by allowing for small amounts of the exhaust gases to be reintroduced into the intake manifold, which decreases the oxygen level in it.

The P0401 means that the exhaust gases are not being recirculated at the desired rate for this system to have wanted results.

This situation leads to the increase of NOx present at the tailpipe, but also the increase of the combustion temperature.

Hotter combustion always leads to the hotter engine, which can cause pre-ignition, a situation in which the air-fuel mixture ignites on its own.

This is a different phenomenon from engine knock, but pre-ignition increases the likelihood of knock, and the damage it can cause to the engine.

Read also: How To Fix P0304 Code in a Chevy?

Causes of the P0401 Code

Many people erroneously assume that this code on Chevys, and many other makes and models, that this code is related only to the EGR valve’s function.

In reality, it means that there is the insufficient flow when the ECM sends the signal to the EGR valve to open.

In Chevy, it is more often related to the other parts of the EGR system.

The most common cause is the blockage of the EGR port on the intake manifold caused by the carbon buildup.

This port is relatively small, and eventually, it will get clogged.

Many of the Chevy models have a cooler for the exhaust gases, which cools them before recirculating them through the intake manifold.

This serves to protect the engine from overheating but also to prevent the pre-ignition.

Over time, the channels of the cooler through which the exhaust gasses travel can become partially or completely clogged by carbon buildup.

The same clogging can happen on the EGR pipe that leads from the cooler to the EGR valve, as the denser and slower-moving gases easier deposit carbon on its surface.

Though the first suspect on Chevy vehicles, the least common cause is failed EGR valve.

It can become clogged by carbon buildup or stuck in a partially open position by fouling, but most common is the failure of the electronic parts of the valve and the inability to be opened.

P0401 EGR insufficient flow >> Check out the video below:

Diagnosis: Reading P0401 Code

Just like any other standard OBD-II code, reading the P0401 is a very simple procedure.

All you need is an OBD scanner and a little bit of time.

When it comes to scanners, you do not need expensive professional handheld devices.

Any kind will be good enough for reading the codes.

The difference between various models is various additional functions, such as sending commands to the engine and its parts.

This is something you do not need for diagnosis, and you can simply grab one of those cheap scanners that connect to a smartphone over the Bluetooth connection.

Once you have a scanner, you need to do is connect it to the OBD-II port on your Chevy, which is most commonly located on the underside of the dashboard.

Once connected you will need to scan the codes and all stored codes will be displayed.

Troubleshooting P0401 Code on Chevy (Step by Step)

To fix any problem you need to troubleshoot for its causes.

Generally, you would go about this by first checking for the most common ones, and then for the less common.

But, because of the engine packaging on many Chevy models that wouldn’t be easy nor sensible.

For example, to check the EGR cooler of Chevy Spark, you need to remove the EGR valve and the exhaust manifold.

Though the failed EGR valve is the least common cause, it only makes sense to check it while removing it to get to the EGR cooler.

So, the troubleshooting procedure on Chevy cars is to go from the easiest accessible parts.

Step #1 Check EGR valve: Checking the EGR valve is easiest done with a 9 volts battery and two jump wires with the alligator clips.

When you remove the connector from the valve you will need to connect one wire to the left-most pin and the positive terminal of the battery.

The other wire to the right-most pin and the negative terminal of the battery.

The engine should be on and idling.

When you close the circuit, you should hear the clicking sound from the valve, and engine RPM should drop.

If there is no clicking and no drop of RPM, the valve’s electronic is dead and needs replacement.

If there is clicking but no drop of RPM, there is clogging somewhere in the EGR system that you can start hunting by visually inspecting the valve’s underside, and clean it if needed.

Step #2 Check EGR pipe: The EGR pipe can get clogged at both ends, and you will have to visually inspect it and remove any considerable carbon buildup.

Step #3 Check EGR cooler: If your Chevy has the EGR cooler, once you get to it you will be able to inspect it for carbon build-up.

If there is a significant amount of it, it will obstruct the flow so you need to clean it.

Step #4 Check EGR port: The most likely cause of the obstructed flow of the EGR system on Chevy cars is the EGR port on the intake manifold.

It is a relatively small port and it will get fouled after around 100,000 miles.

Cleaning it is relatively easy because you need to take off the intake manifold.

But once off, all you need to do is spray it with a brake or carburetor cleaner, or any industrial-strength degreaser, even oven cleaners work well.

Prevent P0401 Code

The P0401 code on Chevys is almost exclusively caused by the clogging of the EGR system.

This happens over time due to the nature of exhaust gases, they contain soot and it gets stuck on various parts of the EGR system.

Fortunately, it takes quite a bit of time for this buildup to become significant enough to trigger this code.

While it is not practical to clean the whole EGR system often, in an effort to prevent it you can take out the intake manifold and EGR cooler, if your car has it, and clean them after some 80,000 to 90,000 miles.

Though the EGR valve can malfunction, it takes much more time for it to happen, and only if you are very unlucky you could have to change it once during the life of your Chevy.

Repair Cost of P0401

If you are fixing the P0401 code on your Chevy, the most important price component is the labor, because on some Chevy models it can take up to three hours.

The replacement gaskets for various components cost less than $5, but if the EGR valve is broken it costs between $150 and $250.

But, the most expensive thing when repairing it at a dealership is the fact that you will certainly be quoted a new EGR valve even if it is not broken.

So, fixing it by yourself can be a more affordable, though time-consuming option.


The P0401 code on Chevy cars, just like in all other makes and models, means that there is insufficient flow through the EGR system.

The most common cause of this is fouling of the EGR port on the intake manifold, which can be easily cleaned.

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Jeff is an automotive technician, technical writer, and Managing Editor. He has held a lifelong passion for cars, with a particular interest in cars like the Buick Reatta. Jeff has been creating written and video content about transportation, automotive, electric cars, future vehicles as well as new, used for more than 18 years. Jeff is based in Boulder, Colorado.

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