WRENCHIFY
Quick decodeBack to home
All codes/P0401

P0401

Exhaust Gas Recirculation (EGR) Flow Insufficient Detected

Moderate severity

This means the system that recirculates exhaust gases back into the engine to reduce emissions isn't working properly, usually because it's clogged with carbon.

The Powertrain Control Module (PCM) has detected that the Exhaust Gas Recirculation (EGR) system is not flowing enough exhaust gas.

Common causes

  • Clogged EGR valve or passages

    Carbon buildup is the most common cause, restricting the flow of exhaust gas.

    high

    Typical part cost: $0-200 part/cleaning

  • Faulty EGR valve

    The valve itself may be stuck closed or not opening sufficiently due to internal failure.

    medium

    Typical part cost: $100-400 part

  • See all causes + fix costs

    Create a free Wrenchify account to unlock the rest for P0401.

    Unlock causes

    Free forever · No credit card

First things to check

  1. 1Inspect EGR valve and passages for carbon buildup
  2. 2Test EGR valve operation (e.g., with a vacuum pump or scan tool)

Get the full step-by-step diagnosis

Create a free Wrenchify account to unlock the rest for P0401.

Unlock diagnosis

Free forever · No credit card

Tools you may need

Already have a compatible scanner? Use it. If not, a Bluetooth OBD2 adapter can help you confirm engine codes and check supported live sensor data before replacing parts.

Illustration of a Bluetooth OBD2 adapter, not a product photo

Basic checks

Veepeak OBDCheck BLE

A Bluetooth LE adapter for reading standard engine codes and supported live data.

View on Amazon
Illustration of a Bluetooth OBD2 adapter, not a product photo

Regular diagnostics

vgate iCar Pro BLE 4.0

A Bluetooth LE adapter with an automatic sleep feature for routine code and sensor checks.

View on Amazon
Illustration of a Bluetooth OBD2 adapter, not a product photo

Another option

OBDLink CX

A Bluetooth LE adapter to consider when comparing supported vehicles and diagnostic apps.

View on Amazon

Illustrations shown, not product photos. Check vehicle, phone and app compatibility before buying. These adapters do not guarantee access to ABS, airbags or manufacturer-specific systems. Clearing a code does not repair the fault and can reset emissions readiness monitors.

As an Amazon Associate, Wrenchify earns from qualifying purchases. This supports the app at no extra cost to you.

Related codes

See related trouble codes

Create a free Wrenchify account to unlock the rest for P0401.

Unlock related codes

Free forever · No credit card

Frequently asked questions

Can I clean an EGR valve?

Yes, often an EGR valve can be removed and cleaned of carbon buildup using carburetor cleaner or a wire brush, which can resolve the P0401 code.

Does P0401 affect fuel economy?

A P0401 code itself might not directly cause a significant drop in fuel economy, but the underlying issue (like engine knocking) can indirectly lead to less efficient combustion.

Get the full P0401 diagnosis for your vehicle

Year, make, model + step-by-step repair help — free plan included.

Diagnose P0401