← View Generic P0400 Guide Severity: Medium
🚗 Vehicle-Specific Guide

This guide is customized for your 2021 Honda PASSPORT

P0400: P0400: Emissions Control System Malfunction

on 2021 Honda PASSPORT

Fix Cost
$100 - $500
Parts & Labor
Difficulty
3/5
1-2 hours
DIY Possible?
✅ Yes
Save money
Your Vehicle
2021 Honda
PASSPORT
⚠️

Important for 2021 Honda PASSPORT Owners

Before starting repairs, verify which engine your 2021 Honda PASSPORT has. Check your VIN or engine code to ensure you order the correct parts.

📖 What Does P0400 Mean on 2021 Honda PASSPORT?

The engine control module (ECM) has detected that the emissions control system is not operating within normal parameters, which can cause increased emissions and potentially harm the environment.
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Symptoms

  • • Rough idle
  • • decreased fuel efficiency
  • • increased emissions
  • • and a check engine light on the dashboard.
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Common Causes

  • • Faulty EGR valve
  • • clogged EGR passages
  • • faulty EGR sensor
  • • or a malfunctioning emissions control module.
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How to Fix P0400 on 2021 Honda PASSPORT

1. Clear any trouble codes and test drive the vehicle to see if the issue persists. 2. Inspect and clean the EGR passages and valve. 3. Replace the EGR valve if it's faulty. 4. Check and replace the EGR sensor if necessary. 5. Update the emissions control module's software if it's outdated.

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Need Maintenance Info for Your PASSPORT?

Get oil capacity, filter specs, and torque settings for your specific 2021 Honda PASSPORT.

View 2021 Honda PASSPORT Specs

Parts for 2021 Honda PASSPORT

EGR valve Shop ↗ EGR sensor Shop ↗ EGR passages cleaning kit Shop ↗

Essential Tool

Must Have

OBD2 Scanner

Read & clear codes on your 2021 Honda PASSPORT

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Related Diagnostic Codes

Other codes that may appear with P0400

P0398 Sequential Code

P0398: Ignition System Misfire

Medium
P0399 Sequential Code

P0399: Ignition System Misfire

Medium
P0401 Sequential Code

Exhaust Gas Recirculation Flow Insufficient Detected

Medium
P0402 Sequential Code

Exhaust Gas Recirculation Flow Excessive Detected

Medium

💡 Why These Codes Are Related:

  • • Similar Issues: Same root cause or component failure
  • • Related Problems: Often occur together due to system interactions
  • • Sequential Codes: Progressive failure stages or multiple sensors
  • • Same System: Components within the same automotive system