AutoCodes – Honda – P0401 Honda

P0401 Honda Code - Exhaust Gas Recirculation Insufficient Flow

Quick Answer

The exhaust gas recirculation (EGR) system reduces oxides of nitrogen (NOx). Common causes include Exhaust Gas Recirculation Valve harness is open or shorted, Exhaust Gas Recirculation Valve circuit poor electrical connection, Faulty Exhaust Gas Recirculation Valve. Severity is Moderate - service should be scheduled soon. The vehicle may still be drivable for short trips if it runs normally, but avoid hard driving and repair it soon.

What it means: P0401 Honda indicates Exhaust Gas Recirculation Insufficient Flow.
Common causes: Common causes include Exhaust Gas Recirculation Valve harness is open or shorted, Exhaust Gas Recirculation Valve circuit poor electrical connection, Faulty Exhaust Gas Recirculation Valve.
Severity: Moderate - service should be scheduled soon.
Can I drive?: The vehicle may still be drivable for short trips if it runs normally, but avoid hard driving and repair it soon.

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Code Popularity 118,320

How popular is this code, among other codes? Medium

Repair Importance Level

Moderate (Service soon) (2 / 3)

Repair Difficulty Level

Intermediate (2 / 3)

What is this?

Table of contents Created and updated by William Orellana on Dec 04, 2022

Description
Step-by-Step Diagnostic Guide
Possible Causes
How To Fix
Tech Notes ▶
Cost to Diagnose
FAQs
Comments
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Code P0401 Honda Description

The exhaust gas recirculation (EGR) system reduces oxides of nitrogen (NOx). NOx is generated by high combustion temperatures.
The EGR system lowers peak combustion temperature by recirculating inactive exhaust gas into the air/fuel mixture, thus reducing NOx emissions.
The EGR valve position sensor is built into the EGR valve and detects the amount of valve lift. The command value for the target valve lift is previously stored in the Powertrain Control Module (PCM) so that exhaust gas recirculation can be optimized according to driving conditions.
Comparing this command value with the EGR valve position sensor output signal value, the PCM controls the EGR valve to make the amount of actual valve lift equal to the command value.
If the EGR valve position sensor output signal value differs greatly from the command value in the PCM memory for a set period of time, the EGR valve or the EGR valve position sensor is considered faulty and a DTC is stored.

OBDII Code P0401 Honda - Exhaust Gas Recirculation Insufficient Flow - AutoCodes.com — P0401 Honda Code - Exhaust Gas Recirculation Insufficient Flow

What does this mean?

What are the Possible Causes of the DTC P0401 Honda?

Exhaust Gas Recirculation Valve harness is open or shorted
Exhaust Gas Recirculation Valve circuit poor electrical connection
Faulty Exhaust Gas Recirculation Valve
Exhaust Gas Recirculation Valve clogged
Exhaust gas leaks

How to Fix the DTC P0401 Honda?

Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.

What does this mean?

Code Tech Notes

In some 1999-2003 Honda Odysseys and 2003 Honda Pilots, the EGR system may become contaminated or clogged. If this happens, the vehicle may hesitate or surge during light acceleration, and the MIL (malfunction indicator lamp) may come on with DTC P0401 (EGR insufficient flow) or P1491 (EGR valve insufficient lift). If DTC P0401 or P1491 is stored, or if the engine hesitates or surges, clean the EGR port, install an EGR pipe kit, and clear the code.

The problem is also common in most 1998-2001 Honda Accord. The factory released a bulletin with instructions on how to clean the intake system.
1998-2001 Honda Accord EGR Port Clogging OBDII Code P0401

P0401, 1999 Acura TL Honda V6

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What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P0401 Honda code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.

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Information for Specific Honda Models

P0401 1998 Honda Accord — Exhaust Gas Recirculation Insufficient Flow
P0401 1999 Honda Accord — Exhaust Gas Recirculation Insufficient Flow
P0401 2000 Honda Accord — Exhaust Gas Recirculation Insufficient Flow
P0401 2001 Honda Accord — Exhaust Gas Recirculation Insufficient Flow
P0401 1996 Honda Civic — Exhaust Gas Recirculation Insufficient Flow
P0401 1997 Honda Civic — Exhaust Gas Recirculation Insufficient Flow
P0401 1998 Honda Civic — Exhaust Gas Recirculation Insufficient Flow
P0401 1999 Honda Civic — Exhaust Gas Recirculation Insufficient Flow
P0401 2000 Honda Civic — Exhaust Gas Recirculation Insufficient Flow

About the author: William Orellana is a Master Mechanic and Mechanical Engineer with over 30 years of experience diagnosing and repairing vehicles. Learn more about his background.

Frequently Asked Questions about P0401 Honda Code

1. What are the common symptoms of OBDII code P0401 (Exhaust Gas Recirculation Insufficient Flow) in a Honda?

The common symptoms include a check engine light, rough idling, decreased fuel efficiency, and potentially, engine knocking or pinging.

2. What are some possible causes of the P0401 code in a Honda vehicle?

Possible causes of the P0401 code in a Honda include a faulty EGR valve, clogged EGR passages, a malfunctioning EGR temperature sensor, or a damaged vacuum hose connected to the EGR system.

3. How can I diagnose the P0401 code in my Honda?

To diagnose the P0401 code, you can use an OBDII scanner to retrieve the code and perform a visual inspection of the EGR system components, check for vacuum leaks, and test the EGR valve and related sensors for proper functioning.

4. Can I drive my Honda with the P0401 code?

While it may be possible to drive your Honda with the P0401 code, it is not recommended as it can lead to decreased engine performance and potential long-term damage. It's best to address the issue promptly.

5. How can I repair the P0401 code in my Honda?

Repairing the P0401 code in a Honda may involve cleaning or replacing the EGR valve, clearing clogged EGR passages, replacing the EGR temperature sensor, or fixing any vacuum leaks in the system.

6. Will resetting the check engine light resolve the P0401 code in my Honda?

Resetting the check engine light may temporarily clear the code, but if the underlying issue causing the P0401 code is not addressed, the code is likely to reappear after some driving cycles.

7. Are there any maintenance tips to prevent the P0401 code in my Honda?

Regularly servicing the EGR system, using high-quality fuel, and ensuring proper engine maintenance can help prevent issues leading to the P0401 code in your Honda.

8. Can a clogged catalytic converter cause the P0401 code in a Honda?

While a clogged catalytic converter can cause related issues, such as engine performance problems, it is not typically a direct cause of the P0401 code. The primary culprits are usually EGR system components.

9. Is it safe to ignore the P0401 code in my Honda?

Ignoring the P0401 code can lead to reduced engine efficiency, increased emissions, and potential long-term damage to the engine. It's best to address the issue promptly to prevent further complications.

10. How much does it cost to repair the P0401 code in a Honda?

The cost of repairing the P0401 code in a Honda can vary depending on the specific cause of the issue, parts needed for replacement, and labor costs. It's recommended to consult a qualified mechanic for an accurate estimate.